Luminescence modulations of rhenium tricarbonyl complexes induced by structural variations

Article abstract of DOI:10.1021/ic5007007

Octahedral d⁶ low-spin Re(I) tricarbonyl complexes are of considerable interest as noninvasive imaging probes and have been deeply studied owing to their biological stability, low toxicity, large Stokes shifts, and long luminescence lifetimes. We reported recently the bimodal IR and luminescence imaging of a Re(I) tricarbonyl complex with a Pyta ligand (4-(2-pyridyl)-1,2,3-triazole) in cells and labeled such metal-carbonyl complexes SCoMPIs for single-core multimodal probes for imaging. Re(I) tricarbonyl complexes have unique photophysical properties allowing for their unequivocal detection in cells but also present some weaknesses such as a very low luminescence quantum yield in aqueous medium. Further optimizations would thus be desirable. We therefore developed new Re(I) tricarbonyl complexes prepared from different ancillary ligands. Complexes with benzothiadiazole- triazole ligands show interesting luminescent quantum yields in acetonitrile and may constitute valuable luminescent metal complexes in organic media. A series of complexes with bidentate 1-(2-quinolinyl)-1,2,3-triazole (Taquin) and 1-(2-pyridyl)-1,2,3-triazole (Tapy) ligands bearing various 4-substituted alkyl side chains has been designed and synthesized with efficient procedures. Their photophysical properties have been characterized in acetonitrile and in a H ₂O/DMSO (98/2) mixture and compared with those of the parent Quinta- and Pyta-based complexes. Tapy complexes bearing long alkyl chains show impressive enhancement of their luminescent properties relative to the parent Pyta complex. Theoretical calculations have been performed to further characterize this new class of rhenium tricarbonyl complexes. Preliminary cellular imaging studies in MDA-MB231 breast cancer cells reveal a strong increase in the luminescence signal in cells incubated with the Tapy complex substituted with a C12 alkyl chain. This study points out the interesting potential of the Tapy ligand in coordination chemistry, which has been so far underexploited.

Full text of DOI:10.1021/ic5007007

Article
pubs.acs.org/IC
Luminescence Modulations of Rhenium Tricarbonyl Complexes
Induced by Structural Variations
Helene C. Bertrand,*,†,‡,§ Sylvain Clede,†,‡,§ Regis Guillot,∥ Francois Lambert,†,‡,§ and Clotilde Policar†,‡,§
̧
́
̀
̀
́
†Sorbonne Universites
‡CNRS, UMR 7203, Laboratoire des Biomolec
́
, UPMC Univ Paris 06, UMR 7203, Laboratoire des Biomolec
ules, F-75005 Paris, France
artement de Chimie, Laboratoire des Biomolecules, 24 rue Lhomond, 75005 Paris, France
Paris-Sud, ICMMO, UMR CNRS 8182, 91405 Orsay, France
́
ules, F-75005 Paris, France
́
§ENS, Dep
́
́
∥Universite
́
S
* Supporting Information
ABSTRACT: Octahedral d6 low-spin Re(I) tricarbonyl
complexes are of considerable interest as noninvasive imaging
probes and have been deeply studied owing to their biological
stability, low toxicity, large Stokes shifts, and long
luminescence lifetimes. We reported recently the bimodal IR
and luminescence imaging of a Re(I) tricarbonyl complex with
a Pyta ligand (4-(2-pyridyl)-1,2,3-triazole) in cells and labeled
such metal−carbonyl complexes SCoMPIs for single-core
multimodal probes for imaging. Re(I) tricarbonyl complexes
have unique photophysical properties allowing for their
unequivocal detection in cells but also present some
weaknesses such as a very low luminescence quantum yield
in aqueous medium. Further optimizations would thus be
desirable. We therefore developed new Re(I) tricarbonyl complexes prepared from different ancillary ligands. Complexes with
benzothiadiazole−triazole ligands show interesting luminescent quantum yields in acetonitrile and may constitute valuable
luminescent metal complexes in organic media. A series of complexes with bidentate 1-(2-quinolinyl)-1,2,3-triazole (Taquin) and
1-(2-pyridyl)-1,2,3-triazole (Tapy) ligands bearing various 4-substituted alkyl side chains has been designed and synthesized with
efficient procedures. Their photophysical properties have been characterized in acetonitrile and in a H2O/DMSO (98/2) mixture
and compared with those of the parent Quinta- and Pyta-based complexes. Tapy complexes bearing long alkyl chains show
impressive enhancement of their luminescent properties relative to the parent Pyta complex. Theoretical calculations have been
performed to further characterize this new class of rhenium tricarbonyl complexes. Preliminary cellular imaging studies in MDA-
MB231 breast cancer cells reveal a strong increase in the luminescence signal in cells incubated with the Tapy complex
substituted with a C12 alkyl chain. This study points out the interesting potential of the Tapy ligand in coordination chemistry,
which has been so far underexploited.
developed with a pendant side chain of different chemical
nature, an alkyl or aromatic group, or a functionalization suitable
for further grafting on a biomolecule.5 Our group recently
reported the use of such metal−carbonyl complexes to couple
infrared and luminescence detection in cells.6 Indeed, a Re(I)
tricarbonyl complex with a Pyta ligand enabled its multimodal
imaging in cells. This bioimaging study is at the origin of the
concept of a single-core multimodal probe for imaging
(SCoMPI).6 This has been successfully applied to the
investigation of the cellular location of an estrogen derivative
conjugate in breast cancer cells.7
INTRODUCTION
■
Organometallic complexes have become of major interest as
noninvasive imaging probes.1 Among them, luminescent
polypyridine-based transition-metal complexes have received
considerable attention, with their photophysical properties
being valuable for bioimaging.2 In particular, octahedral d6
low-spin Re(I) tricarbonyl complexes have been deeply studied
owing to their biological stability, low toxicity, large Stokes
shifts, and long luminescence lifetimes.3 In this class of
compounds, the photophysical properties of the complexes are
closely dependent on the ligand. Originally developed with 2,2′-
bipyridine derivatives, numerous Re(I) tricarbonyl complexes
have been designed that incorporate other aromatic poly-
azaheterocycles2b,4 of easier synthetic access and functionaliza-
tion. In that context the ligand 4-(2-pyridyl)-1,2,3-triazole
(Pyta) has been widely used for the preparation of luminescent
Re(I) complexes. Many functionalized derivatives have been
Re(I) tricarbonyl complexes have unique photophysical
properties allowing for their unequivocal detection in cells but
present also some weaknesses such as a very low luminescence
Received: March 26, 2014
© XXXX American Chemical Society
A
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Inorganic Chemistry
Article
1H NMR (300 MHz, CDCl3): δ (ppm) 9.60 (s, 1H), 8.68 (dd, J =
1.2, 8.1 Hz, 1H), 8.36 (dd, J = 1.5, 8.1 Hz, 1H), 7.97 (td, J = 1.5, 8.1 Hz,
1H), 7.91 (td, J = 1.5, 8.1 Hz, 1H). 13C NMR (75 MHz, CDCl3): δ
(ppm) 142.5, 141.3, 136.9, 131.9, 130.9, 130.0, 125.1, 116.5.
Tetrazolo[1,5-a]quinoline (2). 2-Chloroquinoline (500.0 mg, 3.06
mmol, 1.0 equiv) was dissolved in a DMF/H2O 13/5 mixture (18 mL),
and NaN3 (1.19 g, 18.34 mmol, 6.0 equiv) was added. The mixture was
stirred at 85 °C under Ar for 3 days. The mixture was diluted with H2O
and extracted twice with EtOAc. The organic phase was washed with
H2O, dried over MgSO4, filtered, and evaporated to afford tetrazolo-
[1,5-a]quinoline (2) as a white solid (480.0 mg, 92% chemical yield).
The analytical data were in accordance with those in the literature.8,11
1H NMR (300 MHz, CDCl3): δ (ppm) 8.70 (d, J = 8.4 Hz, 1H), 7.98
(m, 2H), 7.88 (m, 2H), 7.72 (td, J = 1.2 Hz, 8.4 Hz, 1H). 13C NMR (75
MHz, CDCl3): δ (ppm) 133.4, 131.4, 131.0, 129.1, 128.1, 124.0, 117.0,
112.8.
General Procedure A for (CuOTf)2·C6H6-Catalyzed CuAAC Click
Reaction. A vial was charged with the tetrazolo or azido derivative (1.0
equiv) and copper(I) trifluoromethanesulfonate benzene complex (10
mol %). After three vacuum/N2 purges, dry toluene (1.0 mL/0.15
mmol) was added under an inert atmosphere, followed by the alkyne
derivative (1.1 equiv). The vial was closed with a screwed cap and
secured by Teflon tape. The reaction mixture was stirred at 100 °C. The
reaction mixture was then diluted with EtOAc or DCM and H2O. The
organic phase was decanted out, washed with water and saturated brine,
dried over Na2SO4, filtered, and evaporated. The residue was purified
by column chromatography on silica gel to afford the desired
compound.
quantum yield in aqueous medium (typically around 0.7%).
Further optimizations would thus be desirable: a higher
excitation wavelength would allow freeing images from cell
autofluorescence and an increase in the quantum yield in
aqueous medium would be beneficial. We therefore developed
new Re(I) tricarbonyl complexes prepared from different
ancillary ligands. We particularly focused on the 1-(2-pyridyl)-
1,2,3-triazole ligand and derivatives with extended aromatic
surfaces.8 This ligand is called thereafter Tapy by analogy with
Pyta, which is a regioisomer and only differs in the position of
the bridge between the pyridine and the triazole rings. The
coordination properties of such ligands have been surprisingly
overlooked, and no example of rhenium tricarbonyl complexes
incorporating such ligands in their coordination sphere has been
found in the literature. We also developed complexes prepared
from a Tapy analogue, labeled TaBTD, in which the pyridine
ring was substituted with a benzothiadiazole unit.
We present here the synthesis and characterization of these
new ligands along with their corresponding rhenium tricarbonyl
complexes. Their photophysical properties have been studied in
detail, and theoretical studies were performed to further
characterize some of the complexes described. A rhenium
tricarbonyl complex with a Tapy ligand bearing a C12 alkyl
chain showed an unexpectedly high increase in luminescence
intensity and quantum yield in aqueous solution in comparison
to the corresponding Pyta complex. Preliminary imaging studies
show a strong luminescence intensity enhancement in incubated
breast cancer MDA-MB-231 cells.
2-(4-Octyl-1H-1,2,3-triazol-1-yl)quinoxaline (3). This compound
was obtained following the general procedure A starting from
tetrazolo[1,5-a]quinoxaline (1; 26.4 mg, 0.15 mmol, 1.0 equiv) and
1-decyne (30.7 μL, 0.17 mmol, 1.1 equiv) after column chromatog-
raphy on silica gel (eluent cyclohexane/EtOAc 7/3) as a pale yellow
solid (26.0 mg, 55% chemical yield).
EXPERIMENTAL SECTION
■
Chemistry. General Considerations. 1H and 13C NMR spectra
were recorded on a Bruker Avance 300 or 600 spectrometer using
solvent residuals as internal references. The following abbreviations are
used: singlet (s), doublet (d), doublet of doublets (dd), triplet (t),
doublet of triplets (td), quintuplet (quint), sextuplet (sext), and
multiplet (m). Mass spectrometry services were performed at the
Rf (cyclohexane/EtOAc 7/3) = 0.61. 1H NMR (300 MHz, CDCl3):
δ (ppm) 9.81 (s, 1H), 8.46 (s, 1H), 8.17 (m, 1H), 8.03 (m, 1H), 7.81
(m, 2H), 2.85 (td, J = 0.8, 7.5 Hz, 2H), 1.78 (quint, J = 7.5 Hz, 2H),
1.45−1.25 (m, 10H), 0.87 (m, 3H). 13C NMR (75 MHz, CDCl3): δ
(ppm) 149.7, 143.3, 142.3, 140.2, 138.1, 131.6, 130.3, 129.8, 128.9,
118.4, 32.1, 29.6, 29.5 (2C), 27.2, 25.9, 22.9, 14.4. MS (ESI+) m/z (%):
310.2014 (100) [M + H]+, 332.1830 (72) [M + Na]+, 641.3785 (20)
[2M + Na]+.
ICMMO (Universite
́
Paris Sud, Orsay, France) and at UMR7201
(Universite Pierre et Marie Curie). The following abbreviations are
́
used: MS (mass spectrometry), HRMS (high resolution mass
spectrometry), electrospray (ESI), time-of-flight (TOF). TLC analysis
was carried out on silica gel (Merck 60F-254) with visualization at 254
and 366 nm. Preparative flash chromatography was carried out with
Merck silica gel (Si 60, 40−63 μm). Reagents and chemicals were
purchased from Sigma-Aldrich, Alfa Aesar, or Strem Chemicals. Dry
solvents (dichloromethane (CH2Cl2 or DCM), toluene, tetrahydrofur-
an (THF), and dimethylformamide (DMF)) were purchased from
Sigma and used without further purification. UV−vis absorption spectra
were recorded on a Varian Cary 300 Bio spectrophotometer,
luminescence emission spectra on a Jasco FP-8300 spectrofluorometer,
and IR spectra on a Perkin-Elmer Spectrum 100 FT-IR spectrometer.
Analytical HPLC measurements were run on a Dionex Ultimate 3000
instrument using C8A or C18A ACE columns. Though no problem was
encountered in the handling of any of the azides used, these
compounds are potentially explosive and should thus be manipulated
with caution. 2-Methyl-4-(2′-quinolyl)-but-3-yn-2-ol (9) and 2-
ethynylquinoline (10) were synthesized according to published
procedures.9
4-(1-(Quinolin-2-yl)-1H-1,2,3-triazol-4-yl)butan-1-ol (4). This
compound was obtained following the general procedure A at 125
°C for 30 h starting from tetrazolo[1,5-a]quinoline (2; 100.0 mg, 0.59
mmol, 1.0 equiv) and hexyn-1-ol (72.1 μL, 0.65 mmol, 1.1 equiv) after
column chromatography on silica gel (eluent DCM/MeOH 96/4) as a
pale yellow solid (122.6 mg, 78% chemical yield).
1
Rf (DCM/MeOH 94/6) = 0.175. H NMR (300 MHz, CDCl3): δ
(ppm) 8.59 (s, 1H), 8. 35 (s, 2H), 8.04 (d, J = 8.7 Hz, 1H), 7.89 (d, J =
8.1 Hz, 1H), 7.78 (t, J = 8.7 Hz, 1H), 7.59 (t, J = 8.7 Hz, 1H), 3.73 (t, J
= 6.3 Hz, 2H), 2.91 (t, J = 7.5 Hz, 2H), 2.0 (br s, 1H), 1.90 (quint, J =
7.2 Hz, 2H), 1.72 (quint, J = 6.3 Hz, 2H). 13C NMR (75 MHz, CDCl3):
δ (ppm) 148.0, 146.4 (2C), 139.5, 130.7, 128.8, 127.8, 127.76, 127.0,
112.6, 62.3, 32.2, 25.5, 25.4. MS (ESI+) m/z (%): 291.1208 (100) [M +
Na]+.
Hex-5-ynoic Acid. Hex-5-yn-1-ol (1.00 g, 10.2 mmol, 1.0 equiv) was
dissolved in acetone (80 mL) and cooled to 0 °C. Fresh Jones reagent
was added dropwise to the solution with vigorous stirring until the
reacting mixture remained orange. The mixture was warmed to room
temperature, and more Jones reagent was added to maintain the orange
color. One hour after the end of the addition, isopropyl alcohol (15
mL) was added; the mixture was filtered through Celite, and the solvent
was evaporated under reduced pressure. The crude blue oil was
dissolved in Et2O (100 mL) and washed with water (3 × 75 mL). The
organic phase was dried over MgSO4, filtered, and evaporated to afford
hex-5-ynoic acid as a yellow oil (761.0 mg, 67% chemical yield). The
analytical data were in accordance with those in the literature.12
Tetrazolo[1,5-a]quinoxaline (1). 2-Chloroquinoxaline (100.0 mg,
0.607 mmol, 1.0 equiv) was dissolved in DMF (2.6 mL) and NaN3
(237.0 mg, 3.65 mmol, 6.0 equiv) was added. The mixture was stirred at
110 °C under N2 for 24 h. The mixture was diluted with H2O and
extracted twice with EtOAc. The organic phase was washed with
saturated brine, dried over MgSO4, filtered, and evaporated to afford
tetrazolo[1,5-a]quinoxaline (1) as a pale orange solid (98.0 mg, 94%
chemical yield). The analytical data were in accordance with those in
the literature.8,10
B
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1H NMR (300 MHz, CDCl3): δ (ppm) 11.18 (s, 1H), 2.43 (t, J = 7.4
Hz, 2H), 2.20 (t, J = 6.9 Hz, 2H), 1.96 (s, 1H), 1.76 (quint, J = 6.8 Hz,
2H).
7.83 (d, J = 8.1 Hz, 1H), 7.77−7.69 (m, 1H), 7.54 (t, J = 7.5 Hz, 1H),
2.82 (t, J = 7.7 Hz, 2H), 1.76 (quint, J = 7.6 Hz, 2H), 1.48−1.24 (m,
18H), 0.86 (t, J = 6.6 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ (ppm)
149.1, 148.1, 146.4, 139.4, 130.6, 128.8, 127.8, 126.8, 118.2, 112.6, 31.9,
29.70, 29.68, 29.67, 29.59, 29.44, 29.38, 29.32, 29.29, 26.9, 25.8, 22.7,
14.2. MS (ESI+) m/z (%): 365.2684 (100) [M + H]+, 387.2502 (34)
[M + Na]+.
General Procedure B for Rhenium Coordination. The ligand (1.0
equiv) was suspended in anhydrous toluene (1.0 mL for 70.0 μmol)
and heated at 110 °C under N2 until complete dissolution.
Bromopentacarbonylrhenium(I) (1.0 equiv) was added, the color of
the solution changed, and gas was released. The solution was stirred at
110 °C under N2 for 6 h. The mixture was cooled to room temperature
and evaporated. The residue was purified by column chromatography
on silica gel to afford the desired bromotricarbonylrhenium complex.
[ 2 - ( 4 - O c t y l - 1 H - 1 , 2 , 3 - t r i a z o l - 1 - y l ) q u i n o x a l i n e ] -
bromotricarbonylrhenium (A). This compound was obtained
according to general procedure B starting from 2-(4-octyl-1H-1,2,3-
triazol-1-yl)quinoxaline (3; 26.0 mg, 84.0 μmol, 1.0 equiv) after column
chromatography on silica gel (cyclohexane/EtOAc 7/3 to 5/5) as a
deep red solid (47.0 mg, 76% chemical yield).
Methyl Hex-5-ynoate. Hex-5-ynoic acid (761.0 mg, 6.79 mmol, 1.0
equiv) was dissolved in MeOH (2.5 mL) and DCM (8 mL). Three
drops of 95% H2SO4 were added, and the solution was stirred under
reflux for 24 h. The mixture was diluted with DCM (20 mL), and a
saturated aqueous NaHCO3 solution (20 mL) was added. The aqueous
layer was further extracted with DCM (20 mL). The combined organic
layers were dried over MgSO4, filtered, and evaporated. The residue
was purified by column chromatography on silica gel (DCM) to afford
methyl hex-5-ynoate as a colorless oil (712.0 mg, 83% chemical yield).
The analytical data were in accordance with those in the literature.13
1
Rf (DCM) = 0.85. H NMR (300 MHz, CDCl3): δ (ppm) 3.59 (s,
3H), 2.37 (t, J = 7.4 Hz, 2H), 2.18 (t, J = 7.4 Hz, 2H), 1.93 (s, 1H), 1.76
(quint, J = 7.1 Hz, 2H).
Methyl 4-(1-(Quinolin-2-yl)-1H-1,2,3-triazol-4-yl)butanoate (5).
This compound was obtained following the general procedure A at
110 °C for 3 days starting from tetrazolo[1,5-a]quinoline (2; 100.0 mg,
0.59 mmol, 1.0 equiv) and methyl hex-5-ynoate (82.0 mg, 0.65 mmol,
1.12 equiv) after column chromatography on silica gel (eluent DCM/
MeOH 99/1) as a yellow oil (118.0 mg, 67% chemical yield).
Rf (99/1 DCM/methanol) = 0.53. 1H NMR (300 MHz, CDCl3): δ
(ppm) 8.49 (s, 1H), 8.24 (s, 2H), 7.94 (d, J = 8.4 Hz, 1H), 7.78 (d, J =
8.0 Hz, 1H), 7.68 (t, J = 7.7 Hz, 1H), 7.48 (t, J = 7.5 Hz, 1H), 3.61 (s,
3H), 2.82 (t, J = 7.5 Hz, 2H), 2.38 (t, J = 7.4 Hz, 2H), 2.05 (quint, J =
7.4 Hz, 2H). 13C NMR (75 MHz, CDCl3): δ (ppm) 173.7, 148.0,
147.9, 146.5, 139.6, 130.8, 128.9, 127.9, 127.8, 127.0, 118.6, 112.6, 51.7,
33.4, 25.0, 24.5.
4-(1-(Quinolin-2-yl)-1H-1,2,3-triazol-4-yl)butanoic Acid (6). Meth-
yl 4-(1-(quinolin-2-yl)-1H-1,2,3-triazol-4-yl)butanoate (5; 63.0 mg,
0.213 mmol, 1.0 equiv) was dissolved in acetone. An aqueous NaOH
solution was added (680 μL, 0.85 mmol, 4.0 equiv., 5% m/v), and the
solution was stirred at 50 °C under Ar for 16 h. DCM and H2O were
added; the organic phase was discarded and the aqueous phase was
acidified to pH 1 by addition of concentrated HCl. The resulting
precipitate was extracted twice with a DCM/MeOH 9/1 mixture, and
the organic phase was dried over Na2SO4, filtered, and evaporated to
afford 4-(1-(quinolin-2-yl)-1H-1,2,3-triazol-4-yl)butanoic acid (6) as a
white solid (60.0 mg, quantitative chemical yield).
Rf (cyclohexane/EtOAc 5/5) = 0.48. 1H NMR (300 MHz, CDCl3):
δ (ppm) 9.36 (s, 1H), 8.35 (d, J = 8.7 Hz, 1H), 8.49 (s, 1H), 8.33 (d, J =
8.4 Hz, 1H), 8.16 (t, J = 7.5 Hz, 1H), 8.05 (t, J = 7.5 Hz, 1H), 2.92
(tdapp, J = 3.0, 7.5 Hz, 2H), 1.82 (quint, J = 7.5 Hz, 2H), 1.47−1.25 (m,
10H), 0.90 (m, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) 196.3,
193.1, 186.8, 154.1, 143.6, 142.1, 139.7, 135.5, 135.0, 133.2, 131.4,
130.4, 120.8, 32.4, 29.8, 29.7 (2C), 29.1, 26.3, 23.2, 14.7. HRMS (ESI
+): calcd for C21H23BrN5NaO3Re 682.0439, found 682.0413. HPLC (0
to 100% ACN in 30 min, column C8A): rt 26.97 (95%). IR: νmax/cm−1
2033, 1953, 1934, 1915 (CO).
[4-(1-(Quinolin-2-yl)-1H-1,2,3-triazol-4-yl)butan-1-ol]-
bromotricarbonylrhenium(I) (B). This compound was obtained
according to general procedure B starting from 4-(1-(quinolin-2-yl)-
1H-1,2,3-triazol-4-yl)butan-1-ol (4; 75.0 mg, 0.28 mmol, 1.0 equiv)
after filtering, washing with toluene, and drying under vacuum as a
1
bright yellow solid (145.0 mg, 84% chemical yield). H NMR (300
MHz, MeOD): δ (ppm) 9.23 (s, 1H), 8.89 (d, J = 8.7 Hz, 1H), 7.74 (d,
J = 8.7 Hz, 1H), 8.34 (d, J = 8.7 Hz, 1H), 8.20 (dd, J = 1.2, 8.4 Hz, 1H),
8.11 (ddd, J = 1.5, 7.2, 8.7 Hz, 1H), 7.87 (ddd, J = 0.9, 7.2, 8.1 Hz, 1H),
3.66 (t, J = 6.3 Hz, 2H), 2.97 (t, J = 7.5 Hz, 2H), 1.93 (quint, J = 7.5 Hz,
2H), 1.70 (quint, J = 6.3 Hz, 2H). 13C NMR (75 MHz, DMSO-d6): δ
(ppm) 153.5, 149.7, 146.7, 145.1, 134.4, 130.7, 130.4, 129.9, 129.4,
124.1, 112.7, 62.2, 32.6, 25.9 (2C). MS (ESI+) m/z (%): 640.9784 (48)
[M + Na]+, 539.0721 (100) [M − Br]+, 291.1216 (56) [M −
Re(CO)3Br + Na]+. HRMS (ESI+): calcd for C18H16BrN4NaO4Re
640.9810, found 640.9784. HPLC (0 to 100% ACN in 30 min, column
C8A): rt 19.85 (99.2%). IR: νmax/cm−1 2027, 1923, 1903 (CO).
[4-(1-(Quinolin-2-yl)-1H-1,2,3-triazol-4-yl)butanoic acid]-
bromotricarbonylrhenium(I) (C). This compound was obtained
according to general procedure B starting from 4-(1-(quinolin-2-yl)-
1H-1,2,3-triazol-4-yl)butanoic acid (6; 53.0 mg, 0.19 mmol, 1.0 equiv)
after filtering, washing with toluene, and drying under vacuum as a
bright yellow solid (90.0 mg, 76% chemical yield).
1H NMR (300 MHz, DMSO-d6): δ (ppm) 12.14 (br s, 1H), 8.79 (s,
1H), 8.68 (d, J = 8.7 Hz, 1H), 8.28 (d, J = 8.7 Hz, 1H), 8.11 (d, J = 7.2
Hz, 1H), 8.04 (d, J = 8.4 Hz, 1H), 7.87 (t, J = 7.2 Hz, 1H), 7.68 (t, J =
8.4 Hz, 1H), 2.80 (t, J = 7.5 Hz, 2H), 2.33 (t, J = 7.2 Hz, 2H), 1.94
(quint, J = 7.2 Hz, 2H). 13C NMR (75 MHz, DMSO-d6): δ (ppm)
174.1, 147.7, 147.5, 145.7, 140.4, 131.1, 128.2, 127.5, 127.1, 119.1,
112.4, 33.0, 24.3, 24.1. MS (ESI+) m/z (%): 305.0998 (100) [M +
Na]+.
2-(4-Octyl-1H-1,2,3-triazol-1-yl)quinoline (7). This compound was
obtained following the general procedure A starting from tetrazolo[1,5-
a]quinoline (2; 100.0 mg, 0.59 mmol, 1.0 equiv) and 1-decyne (116 μL,
0.645 mmol, 1.1 equiv) after column chromatography on silica gel
(eluent cyclohexane/EtOAc 80/20) as a pale yellow solid (117.0 mg,
56% chemical yield).
Rf (cyclohexane/EtOAc 80/20) = 0.29. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.49 (s, 1H), 8.29 (t, 2H), 7.99 (d, J = 8.4 Hz, 1H),
7.82 (d, J = 8.1 Hz, 1H), 7.72 (t, J = 7.6 Hz, 1H), 7.52 (t, J = 7.5 Hz,
1H), 2.81 (t, J = 7.7 Hz, 2H), 1.75 (quint, J = 7.5 Hz, 2H), 1.58−1.07
(m, 10H), 1.00−0.66 (m, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm)
146.5, 139.5, 130.7, 128.8, 127.84, 127.8, 126.9, 118.3, 112.7, 100.0,
31.9, 29.4, 29.32, 29.28, 29.25, 25.7, 22.7, 14.1. MS (ESI+) m/z (%):
309.2057 (100) [M + H]+, 331.1877 (74) [M + Na]+.
1H NMR (300 MHz, DMSO-d6): δ (ppm) 12.19 (br s, 1H), 9.69 (s,
1H), 9.14 (d, J = 9.0 Hz, 1H), 8.62 (d, J = 8.7 Hz, 1H), 8.58 (d, J = 9.0
Hz, 1H), 8.32 (d, J = 8.4 Hz, 1H), 8.22 (td, J = 1.5, 7.5 Hz, 1H), 7.94 (t,
J = 7.5 Hz, 1H), 2.92 (t, J = 7.5 Hz, 2H), 2.41 (t, J = 7.5 Hz, 2H), 1.99
(quint, J = 7.5 Hz, 2H). 13C NMR (75 MHz, CD3OD): δ (ppm) 183.7,
157.3, 157.1, 155.3, 150.0, 140.7, 137.8, 137.7, 137.0, 136.7, 128.7,
122.0, 42.5, 33.8, 33.6. MS (ESI+) m/z (%): 654.9583 (88) [M + Na]+,
553.0514 (100) [M − Br]+, 305.1014 (88) [M − Re(CO)3Br+Na]+.
HRMS (ESI+): calcd for C18H14BrN4NaO5Re 654.9580, found
640.9583. HPLC (40 to 100% ACN in 30 min, column C18-300): rt
9.64 min (95.5%). IR: νmax/cm−1 2024, 1936, 1884 (CO).
2-(4-Dodecyl-1H-1,2,3-triazol-1-yl)quinoline (8). This compound
was obtained following the general procedure A at 120 °C for 24 h
starting from tetrazolo[1,5-a]quinoline (2; 200.0 mg, 1.18 mmol, 1.0
equiv) and 1-tetradecyne (318 μL, 1.29 mmol, 1.1 equiv) after column
chromatography on silica gel (eluent cyclohexane/EtOAc 80/20) as a
pale yellow solid (323.0 mg, 75% chemical yield).
[ 2 - ( 4 - O c t y l - 1 H - 1 , 2 , 3 - t r i a z o l - 1 - y l ) q u i n o l i n e ] -
bromotricarbonylrhenium(I) (D). This compound was obtained
according to general procedure B starting from 2-(4-octyl-1H-1,2,3-
triazol-1-yl)quinoline (7; 60.0 mg, 195 μmol, 1.0 equiv) after
Rf (eluent cyclohexane/EtOAc 80/20) = 0.30. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.50 (s, 1H), 8.30 (t, 2H), 8.01 (d, J = 8.5 Hz, 1H),
C
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purification by column chromatography on silica gel (cyclohexane/
EtOAc 50/50) as a yellow solid (85 mg, 66% chemical yield).
110 °C under Ar for 4 h. The mixture was diluted with H2O and
extracted twice with DCM. The organic phase was dried over MgSO4,
filtered, and evaporated. The residue was purified by column
chromatography on silica gel (eluent cyclohexane/EtOAc 5/5) to
afford 2-(1-dodecyl-4−1,2,3-triazolyl)quinoline (12) as a pale yellow
solid (15.3 mg, 19% chemical yield).
Rf (cyclohexane/EtOAc 50/50) = 0.34. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.75 (d, J = 8.8 Hz, 1H), 8.49 (t, J = 4.4 Hz, 2H), 8.01
(m, 1H), 7.97−7.86 (m, 2H), 7.74 (t, J = 7.3 Hz, 1H), 2.85−2.62 (m,
2H), 1.69 (tt, J = 12.9, 6.7 Hz, 2H), 1.30 (m, 10H), 0.94−0.82 (m, 3H).
13C NMR (75 MHz, CDCl3): δ (ppm) 196.7, 193.6, 187.3, 153.0,
1H NMR (300 MHz, CDCl3): δ (ppm) 8.34 (m, 2H), 8.23 (d, J = 8.7
Hz, 1H), 8.05 (d, J = 8.7 Hz, 1H), 7.81 (d, J = 8.1 Hz, 1H), 7.70 (ddd, J
= 1.5, 6.9, 8.4 Hz, 1H), 7.51 (ddd, J = 1.2, 6.9, 8.1 Hz, 1H), 4.43 (t, J =
7.2 Hz, 2H), 1.97 (quint, J = 7.2 Hz, 2H), 1.35−1.26 (m, 18H), 0.86 (t,
J = 6.9 Hz, 3H).
147.7, 146.0, 143.7, 134.2, 130.4, 129.4, 129.2, 127.9, 121.3, 111.0, 31.8,
29.21, 29.18, 29.17, 26.9, 25.6, 22.7, 14.2. MS (ESI+) m/z (%):
681.0450 (100) [M + Na]+, 579.1380 (100) [M − Br]+. HRMS (ESI
+): calcd for C22H24BrN4NaO3Re 681.0464, found 681.0450. HPLC
(40 to 100% ACN in 30 min, column C18-300): rt 23.07 (96.6%). IR:
νmax/cm−1 2024, 1923, 1901 (CO).
[6-(4-(Quinolin-2-yl)-1, 2, 3-triazol-1-yl)hexanol]-
bromotricarbonylrhenium(I) (F). This compound was obtained
according to general procedure B starting from 6-(4-(quinolin-2-yl)-
1,2,3-triazol-1-yl)hexanol (11; 25.0 mg, 84.4 μmol, 1.0 equiv) after
purification by column chromatography on silica gel (DCM/MeOH
96/4) as a yellow solid (31.8 mg, 58% chemical yield).
[ 2 - ( 4 - D o d e c y l - 1 H - 1 , 2 , 3 - t r i a z o l - 1 - y l ) q u i n o l i n e ] -
bromotricarbonylrhenium(I) (E). This compound was obtained
according to general procedure B starting from 2-(4-dodecyl-1H-
1,2,3-triazol-1-yl)quinoline (8; 60.0 mg, 165 μmol, 1.0 equiv) after
purification by column chromatography on silica gel (cyclohexane/
EtOAc 50/50) as a yellow solid (86.0 mg, 72% chemical yield).
Rf (cyclohexane/EtOAc 50/50) = 0.36. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.77 (d, J = 8.8 Hz, 1H), 8.48 (d, J = 8.7 Hz, 2H),
8.02 (t, J = 7.6 Hz, 1H), 7.91 (dd, J = 12.4, 8.6 Hz, 2H), 7.75 (t, J = 7.4
Hz, 1H), 2.86−2.63 (m, J = 7.8 Hz, 2H), 1.78−1.58 (m, 2H), 1.48−
1.18 (m, 18H), 0.87 (t, J = 6.6 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ
(ppm) 195.6, 192.4, 186.3, 170.2, 151.9, 146.7, 145.0, 142.5, 133.1,
129.4, 128.3, 128.1, 126.8, 120.1, 109.8, 59.4, 30.9, 28.7, 28.2, 27.6, 25.9,
24.6, 21.7, 20.0, 13.2, 13.1. MS (ESI+) m/z (%): 737.1066 (100) [M +
Na]+. HRMS (ESI+): calcd for C26H32BrN4NaO3Re 737.1091, found
737.1066. HPLC (40 to 100% ACN in 30 min, column C18-300): rt
29.46 (98.1%). IR: νmax/cm−1 2032, 1933, 1904, 1850 (CO).
6-Azidohexan-1-ol. 6-Bromohexan-1-ol (1.0 g, 5.52 mmol, 1.0
equiv) was dissolved in an acetone/H2O 3/1 mixture (20 mL), and
NaN3 (719.0 mg, 11.05 mmol, 2.0 equiv) was added. The solution was
stirred at room temperature under Ar overnight. The mixture was
diluted with H2O and extracted twice with DCM. The organic phase
was washed with saturated brine, dried over MgSO4, filtered, and
evaporated to afford 6-azidohexan-1-ol as a yellow oil (697.0 mg, 88%
chemical yield). The analytical data were in accordance with those in
the literature.14a
1H NMR (300 MHz, d6-acetone): δ (ppm) 9.29 (s, 1H), 8.35 (d, J =
9.0 Hz, 1H), 8.35 (d, J = 8.7 Hz, 1H), 8.31 (d, J = 8.7 Hz, 1H), 8.19 (dd,
J = 1.5, 8.4 Hz, 1H), 8.11 (ddd, J = 1.5, 7.2, 8.7 Hz, 1H), 7.85 (ddd, J =
1.2, 7.2, 8.1 Hz, 1H), 4.77 (t, J = 7.2 Hz, 2H), 3.53 (t, J = 6.0 Hz, 2H),
3.45 (t, J = 5.7 Hz, 1H, OH), 2.12 (q, J = 6.9 Hz, 2H), 1.55−1.48 (m,
6H). 13C NMR (75 MHz, d6-acetone): δ (ppm) 199.0 (CO), 196.5
(CO), 189.7 (CO), 152.9, 151.2, 148.1, 142.1, 133.4, 130.9, 130.2,
129.5, 129.3, 127.4, 120.1, 62.2, 53.0, 33.4, 30.5, 26.7, 26.0; MS (ESI+)
m/z (%): 669.0069 (100) [M + Na]+, 567.1010 (19) [M − Br]+.
HRMS (ESI+): calcd for C20H20BrN4NaO4Re 669.0123, found
669.0069. HPLC (40 to 100% ACN in 20 min, column C18): rt
10.20 (96.5%). IR: νmax/cm−1 2020, 1892 (CO).
[ 2 - ( 1 - D o d e c y l - 1 , 2 , 3 - t r i a z o l - 4 - y l ) q u i n o l i n e ] -
bromotricarbonylrhenium(I) (G). This compound was obtained
according to general procedure B starting from 2-(1-dodecyl-1,2,3-
triazol-4-yl)quinoline (12; 10.0 mg, 27.4 μmol, 1.0 equiv) after
purification by column chromatography on silica gel (DCM) as a
yellow solid (14.9 mg, 76% chemical yield).
1H NMR (300 MHz, d6-acetone): δ (ppm) 9.27 (s, 1H), 8.85−8.80
(m, 2H), 8.31 (d, J = 8.4 Hz, 1H), 8.19 (dd, J = 1.5, 8.1 Hz, 1H), 8.12
(ddd, J = 1.5, 6.9, 8.7 Hz, 1H), 7.86 (ddd, J = 1.2, 6.9, 8.4 Hz, 1H), 4.77
(t, J = 6.9 Hz, 2H), 2.11 (q, J = 6.9 Hz, 2H), 1.46−1.42 (m, 4H), 1.30−
1.26 (m, 14H), 0.86 (t, J = 6.9 Hz, 3H). 13C NMR (75 MHz, d6-
acetone): δ (ppm) 152.9, 151.3, 148.2, 142.2, 133.5, 131.0, 130.3,
129.6, 129.4, 127.5, 120.2, 53.1, 32.7, 30.6, 30.3, 30.1, 27.0, 23.4, 14.4.
MS (ESI+) m/z (%): 737.1078 (100) [M + Na]+. HRMS (ESI+): calcd
for C26H32BrN4NaO3Re 737.1091, found 737.1066. HPLC (40 to
100% ACN in 20 min, column C18): rt 22.65 (100.0%). IR: νmax/cm−1
2022, 1921, 1895, 1854 (CO).
1H NMR (300 MHz, CDCl3): δ (ppm) 3.65 (t, J = 0.6 Hz, 2H), 3.27
(t, J = 0.6 Hz, 2H), 1.60 (m, 4H), 1.40 (m, 4H).
6-(4-(Quinolin-2-yl)-1,2,3-triazol-1-yl)hexanol (11). 2-Ethynylqui-
noline9 (10; 50.0 mg, 0.33 mmol, 1.0 equiv) was suspended in tert-butyl
alcohol (4.4 mL). 6-Azidohexanol (51.5 mg, 0.36 mmol, 1.1 equiv), an
aqueous solution of CuSO4·5H2O (2.056 mL, 32.6 μmol, 0.1 equiv,
from a 4.12 mg mL−1 solution in water), and an aqueous solution of
sodium ascorbate (2.317 mL, 0.098 mmol, 0.3 equiv, from a 8.7 mg
mL−1 solution in water) were then added. The resulting mixture was
stirred at 110 °C under Ar for 4 h. The mixture was diluted with H2O
and extracted twice with DCM. The organic phase was dried over
MgSO4, filtered, and evaporated. The residue was purified by column
chromatography on silica gel (eluent DCM/MeOH 95/5) to afford 6-
(4-(quinolin-2-yl)-1,2,3-triazol-1-yl)-hexanol (11) as a pale yellow solid
(47.7 mg, 49% chemical yield).
Tetrazolo[1,5-a]pyridine (13). Pyridine (808 μL, 10.0 mmol, 1.6
equiv) was added to a mixture of pyridine N-oxide (600.0 mg, 6.3
mmol, 1.0 equiv) and diphenylphosphoryl azide (DPPA; 2.154 mL,
10.0 mmol, 1.6 equiv), and the mixture was stirred at 120 °C under Ar
for 24 h. The mixture was evaporated to dryness and the residue
purified by column chromatography on silica gel (DCM/MeOH 99/1)
to afford tetrazolo[1,5-a]pyridine (13) as a white fluffy solid (718.0 mg,
95%). The analytical data were in accordance with those in the
literature.8
1H NMR (300 MHz, CDCl3): δ (ppm) 8.44 (s, 1H), 8.35 (d, J = 8.7
Hz, 1H), 8.25 (d, J = 8.7 Hz, 1H), 8.09 (d, J = 8.4 Hz, 1H), 7.82 (d, J =
7.8 Hz, 1H), 7.72 (ddd, J = 1.2, 6.9, 8.4 Hz, 1H), 7.52 (t, J = 7.8 Hz,
1H), 4.45 (t, J = 6.9 Hz, 2H), 3.62 (t, J = 6.0 Hz, 2H), 1.98 (quint, J =
6.9 Hz, 2H), 1.56 (quint, J = 6.6 Hz, 2H), 1.48−1.34 (m, 4H). 13C
NMR (75 MHz, CDCl3): δ (ppm) 150.5, 148.3, 147.7, 137.4, 130.1,
128.7, 127.92, 127.0, 126.6, 123.1, 118.8, 62.4, 50.5, 32.4, 30.2, 26.1,
25.1. HRMS (ESI+): calcd for C17H20N4NaO 319.15293, found
319.15288.
Rf (DCM/methanol 99.5/0.5) = 0.84. 1H NMR (300 MHz, CDCl3):
δ (ppm) 8.84 (dt, J = 1.0, 6.9 Hz, 1H), 8.03 (dt, J = 1.0, 9.0 Hz, 1H),
7.68 (ddd, J = 1.0, 6.9, 9.0 Hz, 1H), 7.25 (td, J = 0.9, 6.9 Hz, 1H). 13C
NMR (75 MHz, CDCl3): δ (ppm) 148.6, 132.1, 125.5, 116.8, 116.0.
4-(1-(Pyridin-2-yl)-1H-1,2,3-triazol-4-yl)butan-1-ol (14). This com-
pound was obtained following the general procedure A at 100 °C for 8
h starting from tetrazolo[1,5-a]pyridine (13; 75.0 mg, 0.62 mmol, 1.0
equiv) and hexyn-1-ol (76.6 μL, 0.69 mmol, 1.1 equiv) after column
chromatography on silica gel (eluent DCM/MeOH 94/6) as a yellow
oil (108.0 mg, 79% chemical yield).
2-(1-Dodecyl-1,2,3-triazol-4-yl)quinoline (12). 2-Ethynylquinoline9
(10; 34.0 mg, 0.22 mmol, 1.0 equiv) was suspended in tert-butyl alcohol
(3.0 mL). 1-Dodecyl azide (51.5 mg, 0.24 mmol, 1.1 equiv), an aqueous
solution of CuSO4·5H2O (1.40 mL, 22.2 μmol, 0.1 equiv., from a 4.12
mg mL−1 solution in water), and an aqueous solution of sodium
ascorbate (1.575 mL, 0.067 mmol, 0.3 equiv, from a 8.7 mg mL−1
solution in water) were then added. The resulting mixture was stirred at
1H NMR (300 MHz, CDCl3): δ (ppm) 8.33 (ddd, J = 0.6, 1.8, 4.8
Hz, 1H), 8.22 (s, 1H), 8.01 (d, J = 8.4 Hz, 1H), 7.77 (ddd, J = 1.8, 7.5,
8.1 Hz, 1H), 7.19 (ddd, J = 0.9, 4.8, 7.5 Hz, 1H), 3.60 (t, J = 6.3 Hz,
2H), 2.72 (t, J = 7.5 Hz, 2H), 1.73 (quint, J = 7.5 Hz, 2H), 1.56 (quint, J
= 6.3 Hz, 2H). 13C NMR (75 MHz, CDCl3): δ (ppm) 149.1, 148.5,
D
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148.4, 139.1, 123.4, 118.3, 113.6, 61.9, 32.1, 25.5, 25.3. MS (ESI+) m/z
(%): 241.1055 (100) [M + Na]+.
153.3, 152.8, 147.5, 141.9, 125.8, 120.1, 113.4, 30.8, 25.5, 22.4, 13.9. MS
(ESI+) m/z (%): 574.9681 (100) [M + Na]+, 225.1108 (76) [M −
Re(CO)3Br + Na]+. HRMS (ESI+): calcd for C14H14BrN4NaO3Re
574.9682, found 574.9681. HPLC (40 to 100% ACN in 30 min,
column C18A): rt 11.807 (87.6%), IR: νmax/cm−1 2025, 1896 (CO),
[ 2 - ( 4 - O c t y l - 1 H - 1 , 2 , 3 - t r i a z o l - 1 - y l ) p y r i d i n e ] -
bromotricarbonylrhenium(I) (J). This compound was obtained
according to general procedure B starting from 2-(4-octyl-1H-1,2,3-
triazol-1-yl)pyridine (16; 60.0 mg, 232 μmol, 1.0 equiv) after
purification by column chromatography on silica gel (cyclohexane/
EtOAc 50/50) as a yellow solid (123.0 mg, 87% chemical yield).
Rf (cyclohexane/EtOAc 50/50) = 0.28. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.95−8.88 (dd, 1H), 8.34 (s, 1H), 8.18 (td, J = 8.3,
1.6 Hz, 1H), 7.91 (d, J = 8.3 Hz, 1H), 7.56−7.48 (m, 1H), 2.89−2.67
(m, 2H), 1.72 (p, J = 8.0, 7.5 Hz, 2H), 1.47−1.17 (m, 10H), 0.94−0.81
(m, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) 195.9, 194.0, 187.3,
152.9, 152.7, 147.4, 142.0, 125.7, 120.3, 113.5, 60.4, 31.8, 29.2, 28.6,
26.9, 25.7, 22.7, 14.1. MS (ESI+) m/z (%): 1137.1619 (32) [2M −
Br]+, 631.0297 (100) [M + Na]+, 529.1231 (68) [M − Br]+, 281.1739
(32) [M − Re(CO)3Br + Na]+. HRMS (ESI+): calcd for
C18H22BrN4NaO3Re 631.0308, found 631.0297. HPLC (40 to 100%
ACN in 30 min, column C18-300): rt 20.47 (96.3%). IR: νmax/cm−1
2023, 1919, 1916, 1885 (CO).
[ 2 - ( 4 - D o d e c y l - 1 H - 1 , 2 , 3 - t r i a z o l - 1 - y l ) p y r i d i n e ] -
bromotricarbonylrhenium(I) (K). This compound was obtained
according to general procedure B starting from 2-(4-dodecyl-1H-
1,2,3-triazol-1-yl)pyridine (17; 100.0 mg, 318 μmol, 1.0 equiv) after
purification by column chromatography on silica gel (cyclohexane/
EtOAc 50/50) as a yellow solid (169.0 mg, 80% chemical yield).
Rf (cyclohexane/EtOAc 50/50) = 0.30. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.95 (d, J = 5.3 Hz, 1H), 8.25 (s, 1H), 8.17 (t, J = 7.8
Hz, 1H), 7.84 (d, J = 8.2 Hz, 1H), 7.58−7.46 (m, 1H), 2.82 (h, J = 7.6
Hz, 2H), 1.73 (q, J = 7.7, 7.3 Hz, 2H), 1.26 (s, 18H), 0.88 (t, J = 6.4 Hz,
3H). 13C NMR (75 MHz, CDCl3): δ (ppm) 186.3, 152.0, 151.7, 146.4,
140.8, 124.6, 119.0, 112.3, 30.9, 28.64, 28.62, 28.61, 28.5, 28.3, 28.24,
28.19, 27.6, 24.7, 21.7, 13.1. MS (ESI+) m/z (%): 687.0920 (100) [M +
Na]+. HRMS (ESI+): calcd for C22H30BrN4NaO3Re 687.0934, found
687.0920. HPLC (20 to 100% ACN in 20 min, column C18 A): 23.747
min (91.4%). IR: νmax/cm−1 2022, 1918, 1896, 1886 (CO).
2-(4-Butyl-1H-1,2,3-triazol-1-yl)pyridine (15). This compound was
obtained following the general procedure A at 110 °C for 48 h starting
from tetrazolo[1,5-a]pyridine (13; 70.0 mg, 0.58 mmol, 1.0 equiv) and
1-hexyne (73.7 μL, 0.64 mmol, 1.1 equiv) after column chromatog-
raphy on silica gel (cyclohexane/EtOAc 70/30) as a brown oil (77.0
mg, 65% chemical yield).
Rf (cyclohexane/EtOAc 70/30) = 0.76. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.42 (m, 1H), 8.27 (s, 1H), 8.12 (m, 1H), 7.84 (m,
1H), 7.26 (m, 1H), 2.76 (t, J = 7.5 Hz, 2H), 1.67 (quint, J = 7.5 Hz,
2H), 1.36 (sext, J = 7.5 Hz, 2H), 0.89 (t, J = 7.5 Hz, 3H). 13C NMR (75
MHz, CDCl3): δ (ppm) 149.3, 149.2, 148.4, 139.0, 123.3, 118.2, 113.7,
31.4, 25.4, 22.2, 13.8. MS (ESI+) m/z (%): 203.1286 (100) [M + H]+,
225.1108 (64) [M + Na]+.
2-(4-Octyl-1H-1,2,3-triazol-1-yl)pyridine (16). This compound was
obtained following the general procedure A at 120 °C for 24 h starting
from tetrazolo[1,5-a]pyridine (13; 100.0 mg, 0.833 mmol, 1.0 equiv)
and 1-decyne (166 μL, 0.92 mmol, 1.1 equiv) after column
chromatography on silica gel (cyclohexane/EtOAc 80/20) as a pale
yellow solid (135.0 mg, 62% chemical yield).
Rf (cyclohexane/EtOAc 80/20) = 0.13. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.46 (d, J = 4.9, 1.7 Hz, 1H), 8.29 (s, 1H), 8.16 (d, J =
8.2 Hz, 1H), 7.87 (td, J = 7.8, 1.8 Hz, 1H), 7.34−7.27 (m, 1H), 2.78 (t,
J = 7.6 Hz, 2H), 1.71 (q, J = 7.8 Hz, 2H), 1.46−1.21 (m, 10 H), 0.95−
0.82 (m, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) 149.4, 149.0,
148.4, 139.0, 123.2, 118.1, 113.7, 31.9, 29.4, 29.3, 29.2, 25.7, 22.7, 14.1.
MS (ESI+) m/z (%): 259.1902 (100) [M + H]+, 281.1722 (83) [M +
Na]+.
2-(4-Dodecyl-1H-1,2,3-triazol-1-yl)pyridine (17). This compound
was obtained following the general procedure A at 120 °C for 24 h
starting from tetrazolo[1,5-a]pyridine (13; 150.0 mg, 1.25 mmol, 1.0
equiv) and 1-tetradecyne (341 μL, 1.38 mmol, 1.1 equiv) after column
chromatography on silica gel (cyclohexane/EtOAc 80/20) as a pale
yellow solid (278.0 mg, 70% chemical yield).
Rf (cyclohexane/EtOAc 80/20) = 0.12. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.37 (d, J = 4.1 Hz, 1H), 8.21 (s, 1H), 8.07 (d, J = 8.2
Hz, 1H), 7.78 (t, J = 8.6 Hz, 1H), 7.2 (dd, 1H), 2.70 (t, J = 7.6 Hz, 2H),
1.64 (p, J = 7.5 Hz, 2 H), 1.24 (d, J = 48.3 Hz, 18 H), 0.77 (t, J = 6.5 Hz,
3H). 13C NMR (75 MHz, CDCl3): δ (ppm) 149.3, 148.8, 148.4, 138.9,
123.1, 118.0, 113.6, 31.9, 29.7, 29.6, 29.5, 29.4, 29.33, 29.25, 29.19, 26.9,
25.6, 22.7, 14.1. MS (ESI+) m/z (%): 315.2529 (100) [M + H]+,
337.2349 (69) [M + Na]+.
[ 2 - ( 4 - D o d e c y l - 1 H - 1 , 2 , 3 - t r i a z o l - 1 - y l ) p y r i d i n e ] -
chlorotricarbonylrhenium(I) (L). This compound was obtained
according to an adapted general procedure B starting from 2-(4-
dodecyl-1H-1,2,3-triazol-1-yl)pyridine (17; 28.0 mg, 92.1 μmol, 1.0
equiv) and chloropentacarbonylrhenium(I) (35.0 mg, 96.7 μmol, 1.05
equiv) after purification by column chromatography on silica gel
(cyclohexane/EtOAc 30/70) as a yellow solid (44.0 mg, 77% chemical
yield).
[4-(1-(Pyridin-2-yl)-1H-1,2,3-triazol-4-yl)butan-1-ol]-
bromotricarbonylrhenium(I) (H). This compound was obtained
according to general procedure B starting from 4-(1-(pyridin-2-yl)-
1H-1,2,3-triazol-4-yl)butan-1-ol (14; 70.0 mg, 0.32 mmol, 1.0 equiv)
after purification by column chromatography on silica gel (DCM/
MeOH 92/8) as a bright yellow solid (138.0 mg, 86% chemical yield).
1H NMR (300 MHz, MeOD): δ (ppm) 9.05 (s, 1H), 8.92 (d, J = 4.8
Hz, 1H), 8.34 (tapp, J = 4.8 Hz, 1H), 8.26 (d, J = 5.1 Hz, 1H), 7.66 (t, J =
6.6 Hz, 1H), 3.62 (t, J = 6.3 Hz, 2H), 2.90 (t, J = 7.5 Hz, 2H), 1.86
(quint, J = 7.5 Hz, 2H), 1.66 (quint, J = 6.3 Hz, 2H). 13C NMR (75
MHz, MeOD): δ (ppm) 153.6, 153.1, 148.8, 143.6, 127.0, 123.2, 115.2,
62.2, 32.6, 25.94, 25.91. MS (ESI+) m/z (%): 590.9636 (96) [M +
Na]+, 489.0569 (100) [M − Br]+, 241.1063 (68) [M − Re(CO)3Br
+Na]+. HRMS (ESI+): calcd for C14H14BrN4NaO4Re 590.9631, found
590.9636. HPLC (0 to 100% ACN in 30 min, column C8A): rt 17.57
(90.8%). IR: νmax/cm−1 2022, 1934, 1884 (CO).
[ 2 - ( 4 - B u t y l - 1 H - 1 , 2 , 3 - t r i a z o l - 1 - y l ) p y r i d i n e ] -
bromotricarbonylrhenium(I) (I). This compound was obtained
according to general procedure B starting from 2-(4-butyl-1H-1,2,3-
triazol-1-yl)pyridine (15; 30.0 mg, 148 μmol, 1.0 equiv) after
purification by column chromatography on silica gel (cyclohexane/
EtOAc 30/70) as a yellow solid (59.5 mg, 73% chemical yield).
Rf (cyclohexane/EtOAc 30/70) = 0.24. 1H NMR (300 MHz,
CDCl3): δ (ppm) 8.60 (dd, J = 1.2, 5.4 Hz, 1H), 8.24 (s, 1H), 8.18
(tdapp, J = 1.2, 5.4 Hz, 1H), 7.83 (d, J = 8.1 Hz, 1H), 7.57−7.52 (m,
1H), 2.87−2.81 (m, 2H), 1.77−1.69 (m, 2H), 1.45 (sext, J = 7.5 Hz,
2H), 0.97 (t, J = 7.5 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm)
1H NMR (300 MHz, CDCl3): δ (ppm) 8.89 (d, J = 5.4 Hz, 1H), 8.12
(m, 2H), 7.74 (d, J = 8.1 Hz, 1H), 7.47 (dd, J = 5.7, 7.2 Hz, 1H), 2.75
(m, 2H), 1.68 (quint, J = 7.2 Hz, 2H), 1.23 (m, 18H), 0.81 (t, J = 6.9
Hz, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) 153.2, 152.8, 147.7,
141.9, 125.8, 120.2, 113.4, 32.0, 29.79, 29.77, 29.76, 29.6, 29.5, 29.4,
29.36, 28.8, 25.8, 22.8, 14.3. MS (ESI+) m/z (%): 899.4322 (52)
[L2Re(CO)3]+, 643.1432 (100) [M + Na]+, 585.1859 (48) [M − Cl]+,
337.2349 (48) [M − Re(CO)3Cl + Na]+. HRMS (ESI+): calcd for
C22H30ClN4NaO3Re 643.1448, found 643.1432. HPLC (40 to 100%
ACN in 30 min, column C18A): rt 21.754 (100%). IR: νmax/cm−1 2028,
1914 (CO).
4-Bromobenzo[c][1,2,5]thiadiazole (18). Benzothiadiazole (1.0 g,
7.34 mmol, 1.0 equiv) was suspended in HBr (33% in AcOH, 13 mL),
and the mixture was stirred at 100 °C. Bromine (414 μL, 8.08 mmol,
1.1 equiv) was added slowly at 100 °C, and the solution was stirred at
115 °C for 2 h. Bromine (138 μL) was again added, and the mixture
was stirred at 140 °C for 3.5 h. The mixture was diluted with H2O; a
saturated aqueous Na2S2O5 solution was added until the discoloration
was complete, and the solution was extracted with Et2O and DCM. The
combined organic phases were dried over MgSO4, filtered, and
evaporated. The residue was purified by column chromatoghaphy on
silica gel (SiO2, eluent cyclohexane/EtOAc 9/1). The fractions
containing the desired compound were combined and evaporated.
E
dx.doi.org/10.1021/ic5007007 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
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The residue was taken up in the minimum amount of EtOH. Successive
recrystallizations afforded 4-bromobenzo[c][1,2,5]thiadiazole (18) as a
white solid (352.0 mg, 22% chemical yield). The analytical data were in
accordance with those in the literature.15
DCM) to afford 4-(1-dodecyl-1H-1,2,3-triazol-4-yl)benzo[c][1,2,5]-
thiadiazole 21 as a colorless solid (24.0 mg, 80% chemical yield).
Rf (DCM/MeOH 98/2) = 0.74. H NMR (300 MHz, CDCl3): δ
(ppm) 8.74 (s, 1H), 8.56 (dd, J = 0.9 Hz, 6.9 Hz, 1H), 7.97 (dd, J = 0.9
Hz, 8.7 Hz, 1H), 7.71 (dd, J = 6.9 Hz, 8.7 Hz, 1H), 4.48 (t, J = 7.2 Hz,
2H), 2.02 (quint, J = 7.2 Hz, 2H), 1.35 (m, 18H), 0.87 (t, J = 6.9 Hz,
3H). 13C NMR (75 MHz, CDCl3): δ (ppm) 155.4, 152.0, 143.2, 130.1,
125.5, 124.0, 123.8, 120.7, 50.7, 32.0, 30.5, 29.7, 29.6, 29.5, 29.4, 29.1,
26.6, 22.8, 14.2. HRMS (ESI+): calcd for C20H29N5NaS 394.2036,
found 394.2040.
1
1H NMR (300 MHz, CDCl3): δ (ppm) 7.97 (dd, J = 0.9 Hz, 8.7 Hz,
1H), 7.84 (dd, J = 0.6 Hz, 7.2 Hz, 1H), 7.48 (dd, J = 7.5 Hz, 9.0 Hz,
1H).
4-Ethynylbenzo[c][1,2,5]thiadiazole (19). 4-Bromobenzo[c]-
[1,2,5]thiadiazole (18; 150.0 mg, 0.70 mmol, 1.0 equiv) was dissolved
in dry DMF (1.5 mL) and Et3N (1.5 mL), and the solution was
degassed and bubbled with Ar for 10 min. CuI (13.3 mg, 0.07 mmol, 0.1
equiv), Pd(PPh3)4 (40.3 mg, 0.035 mmol, 0.05 equiv), and
(trimethylsilyl)acetylene (149 μL, 1.05 mmol, 1.5 equiv) were
successively added, and the resulting pale orange mixture was stirred
under Ar at 70 °C overnight. The mixture was evporated and the
residue purified by column chromatography on silica gel (eluent DCM/
petroleum ether 7/3) to afford 4-((trimethylsilyl)ethynyl)benzo[c]-
[1,2,5]thiadiazole as a brownish yellow solid (55.0 mg, traces of starting
material, used in the next step without further purification). The
analytical data were in accordance with those in the literature.16
Rf (DCM/petroleum ether 7/3) = 0.59. 1H NMR (300 MHz,
CDCl3): δ (ppm) 7.99 (dd, J = 1.2 Hz, 8.7 Hz, 1H), 7.77 (dd, J = 1.2
Hz, 7.2 Hz, 1H), 7.55 (dd, J = 7.2 Hz, 8.7 Hz, 1H), 0.34 (s, 9H).
4-((Trimethylsilyl)ethynyl)benzo[c][1,2,5]thiadiazole (61.0 mg,
0.26 mmol, 1.0 equiv) was dissolved in MeOH (4 mL). K2CO3 (36.3
mg, 0.26 mmol, 1.0 equiv) was added, and the solution was stirred at
room temperature under Ar for 2 h. The mixture was diluted with H2O
and extracted twice with DCM. The organic phase was dried over
MgSO4, filtered, and evaporated. The residue was purified by column
chromatography on silica gel (eluent cyclohexane/EtOAc 9/1) to
afford 4-ethynylbenzo[c][1,2,5]thiadiazole (19) as a yellowish solid
(25.0 mg, 34% chemical yield over two steps).
[6-(4-(Benzo[c][1,2,5]thiadiazol-4-yl)-1H-1,2,3-triazol-1-yl)hexan-
1-ol]bromotricarbonylrhenium(I) (N). This compound was obtained
according to general procedure B starting from 6-(4-(benzo[c][1,2,5]-
thiadiazol-4-yl)-1H-1,2,3-triazol-1-yl)hexan-1-ol (20; 23.9 mg, 78.8
μmol, 1.0 equiv) after filtering, washing with toluene, and drying under
vacuum as a bright orange solid (35.2 mg, 68% chemical yield).
1H NMR (300 MHz, acetone-d6): δ (ppm) 9.22 (s, 1H), 8.45 (dd, J
= 0.9 Hz, 7.2 Hz, 1H), 8.26 (dd, J = 0.9 Hz, 9.0 Hz, 1H), 7.98 (dd, J =
7.2 Hz, 9.0 Hz, 1H), 4.71 (t, J = 7.2 Hz, 2H), 3.52 (t, J = 6.0 Hz, 2H),
2.10 (m, 2H), 1.52−1.44 (m, 6H). 13C NMR (75 MHz, CD3OD): δ
(ppm) 155.5, 147.6, 142.0, 132.2, 129.9, 125.1, 124.6, 121.4, 62.7, 53.0,
33.3, 30.7, 27.1, 26.2. MS (ESI+) m/z (%): 574.0547 (100) [M − Br]+,
675.9619 (80) [M
+
Na]+. HRMS (ESI+): calcd for
C17H17BrN5NaO4ReS 675.9616, found 675.9619. HPLC (0 to 100%
ACN in 30 min, column C8A): rt 19.96 (92.9%). IR: νmax/cm−1 2022,
1916, 1889 (CO).
[4-(1-Dodecyl-1H-1,2,3-triazol-4-yl)benzo[c][1,2,5]thiadiazole]-
bromotricarbonylrhenium(I) (O). This compound was obtained
according to general procedure B starting from 4-(1-dodecyl-1H-
1,2,3-triazol-4-yl)benzo[c][1,2,5]thiadiazole (21; 10.4 mg, 28.0 μmol,
1.0 equiv) after purification by column chromatography on silica gel
(cyclohexane/EtOAc 30/70) as a bright orange solid (16.0 mg, 79%
chemical yield).
Rf (cyclohexane/EtOAc 9/1) = 0.30. 1H NMR (300 MHz, CDCl3):
δ (ppm) 8.02 (dd, J = 0.9 Hz, 8.7 Hz, 1H), 7.78 (dd, J = 0.9 Hz, 6.9 Hz,
1H), 7.55 (dd, J = 6.9 Hz, 9.0 Hz, 1H), 3.59 (s, 1H). 13C NMR (75
MHz, CDCl3): δ (ppm) 154.8, 154.5, 133.8, 129.1, 122.7, 116.0, 83.7,
79.2.
1H NMR (300 MHz, d6-acetone): δ (ppm) 9.22 (s, 1H), 8.46 (dd, J
= 0.9 Hz, 7.2 Hz, 1H), 8.27 (dd, J = 0.9 Hz, 9.0 Hz, 1H), 8.00 (dd, J =
7.2 Hz, 9.0 Hz, 1H), 4.71 (t, J = 7.2 Hz, 2H), 2.10 (m, 2H), 1.44−1.26
(m, 18H), 0.86 (t, J = 7.2 Hz, 3H). 13C NMR (75 MHz, CD3OD): δ
(ppm) 154.2, 146.3, 140.8, 130.6, 127.9, 124.2, 121.9, 120.1, 52.4, 32.0,
29.91, 29.85, 29.7, 29.6, 29.5, 29.0, 26.5, 22.8, 14.3. HRMS (ESI+):
calcd for C23H29BrN5NaO3ReS 744.0606, found 744.0591. HPLC (40
6-(4-(Benzo[c][1,2,5]thiadiazol-4-yl)-1H-1,2,3-triazol-1-yl)hexan-
1-ol (20). 4-Ethynylbenzo[c][1,2,5]thiadiazole (19; 20.0 mg, 0.12
mmol, 1.0 equiv) was suspended in tert-butyl alcohol (1.7 mL). 6-
Azidohexanol (18.8 mg, 0.13 mmol, 1.05 equiv), an aqueous solution of
CuSO4·5H2O (757.0 μL, 12.0 μmol, 0.1 equiv, from a 4.12 mg mL−1
solution in water), and an aqueous solution of sodium ascorbate (853.0
μL, 0.036 mmol, 0.3 equiv, from a 8.7 mg mL−1 solution in water) were
then added. The resulting mixture was stirred at 110 °C under Ar
overnight. The mixture was diluted with H2O and extracted twice with
DCM. The organic phase was dried over MgSO4, filtered, and
evaporated. The residue iswas purified by column chromatography on
silica gel (eluent DCM/MeOH 94/6) to afford 6-(4-(benzo[c][1,2,5]-
thiadiazol-4-yl)-1H-1,2,3-triazol-1-yl)hexan-1-ol (20) as a yellow solid
(34.0 mg, 90% chemical yield).
to 100% ACN in 20 min, column C18): rt 22.22 (97.5%). IR: νmax
/
cm−1 2040, 2026, 1936, 1918, 1897 (CO).
4-Azidobenzo[c][1,2,5]thiadiazole (22). 4-Aminobenzo[c][1,2,5]-
thiadiazole (500.0 mg, 3.31 mmol, 1.0 equiv) was suspended in water
(10.0 mL); concentrated aqueous HCl was added (1.0 mL), and the
solution was cooled at 0 °C. A solution of NaNO2 (274.0 mg, 3.97
mmol, 1.2 equiv) in water (1.5 mL) was added dropwise at 0 °C, and
the mixture was further stirred for 20 min. A solution of NaN3 (322.5
mg, 4.96 mmol, 1.5 equiv) in water (1.5 mL) was added dropwise at 0
°C, and the obtained suspension was stirred for 3 h. The solution was
extracted with Et2O; the organic phase was washed with saturated
brine, dried over MgSO4, filtered, and concentrated under reduced
pressure. The residue was purified by column chromatography on silica
gel (DCM) to afford 4-azidobenzo[c][1,2,5]thiadiazole (22) as a
brown solid (150.0 mg, 26% chemical yield).
1
Rf (DCM/MeOH 94/6) = 0.26. H NMR (300 MHz, CDCl3): δ
(ppm) 8.76 (s, 1H), 8.57 (dd, J = 0.9 Hz, 6.9 Hz, 1H), 7.99 (dd, J = 0.9
Hz, 8.7 Hz, 1H), 7.73 (dd, J = 6.9 Hz, 8.7 Hz, 1H), 4.51 (t, J = 7.2 Hz,
2H), 3.65 (t, J = 6.3 Hz, 2H), 2.05 (quint, J = 7.2 Hz, 2H), 1.60 (m,
2H), 1.45 (m, 4H). 13C NMR (75 MHz, CDCl3): δ (ppm) 155.6,
152.1, 143.3, 130.3, 125.7, 124.2, 123.7, 121.0, 62.9, 50.7, 32.6, 30.6,
26.5, 25.4. MS (ESI+) m/z (%): 304.1222 (15) [M + H]+, 326.1044
(100) [M + Na]+.
Rf (DCM) = 0.79. 1H NMR (300 MHz, CDCl3): δ (ppm) 7.35 (dd, J
= 0.9, 8.7 Hz, 1H), 7.51 (dd, J = 1.2, 7.2 Hz, 1H), 7.09 (dd, J = 0.9, 7.5
Hz, 1H). 13C NMR (75 MHz, CDCl3): δ (ppm) 155.9, 149.1, 132.0,
129.7, 117.6, 116.5.
4-(1-Dodecyl-1H-1,2,3-triazol-4-yl)benzo[c][1,2,5]thiadiazole
(21). 4-Ethynylbenzo[c][1,2,5]thiadiazole (19; 13.0 mg, 0.081 mmol,
1.0 equiv) was suspended in tert-butyl alcohol (1.1 mL). 1-Dodecyl
azide (18.0 mg, 0.085 mmol, 1.05 equiv), an aqueous solution of
CuSO4·5H2O (491.0 μL, 8.1 μmol, 0.1 equiv, from a 4.12 mg mL−1
solution in water) and an aqueous solution of sodium ascorbate (554.0
μL, 24.3 μmol, 0.3 equiv, from a 8.7 mg mL−1 solution in water) were
then added. The resulting mixture was stirred at 110 °C under Ar for 30
h. The mixture was diluted with H2O and extracted twice with DCM.
The organic phase was dried over MgSO4, filtered, and evaporated. The
residue was purified by column chromatography on silica gel (eluent
4-(4-Dodecyl-1H-1,2,3-triazol-1-yl)benzo[c][1,2,5]thiadiazole
(23). This compound was obtained following general procedure A at
100 °C for 4 days starting from 4-azidobenzo[c][1,2,5]thiadiazole (22;
35.0 mg, 0.198 mmol, 1.0 equiv) and 1-tetradecyne (53.5 μL, 0.217
mmol, 1.1 equiv) after purification by column chromatography on silica
gel (cyclohexane/EtOAc 85/15) as a pale yellow solid (41.0 mg, 56%
chemical yield).
1H NMR (300 MHz, CDCl3): δ (ppm) 8.83 (s, 1H), 8.39 (d, J = 7.2
Hz, 1H), 8.05 (d, J = 8.7 Hz, 1H), 7.76 (tapp, J = 8.1 Hz, 1H), 2.86 (t, J =
7.5 Hz, 2H), 1.79 (quint, J = 7.5 Hz, 2H), 1.34 (m, 18H), 0.86 (t, J = 6.9
Hz, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) 155.9, 149.0, 146.8,
F
dx.doi.org/10.1021/ic5007007 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 1. Structures of the ligands used in this study.
129.7, 128.8, 122.4, 121.2, 120.3, 32.0, 29.8, 29.77 (2C), 29.7, 29.5,
29.48 (2C), 29.4, 25.8, 22.8, 14.2.
Luminescence Quantum Yield Determination. Luminescence
emission studies were performed on a Jasco FP-8300 spectrofluor-
ometer. Emission spectra were recorded at two concentrations and for
three different excitation wavelengths (at the absorption maximum
λabsmax and around λabsmax − 10 and λabsmax + 10). The average integrated
emission area F for the six measurements is used to determine the
quantum yield in the equation
[4-(4-Dodecyl-1H-1,2,3-triazol-1-yl)benzo[c][1,2,5]thiadiazole]-
bromotricarbonylrhenium(I) (P). This compound was obtained
according to general procedure B starting from 4-(4-dodecyl-1H-
1,2,3-triazol-1-yl)benzo[c][1,2,5]thiadiazole (23; 8.1 mg, 27.0 μmol,
1.0 equiv) after purification by column chromatography on silica gel
(cyclohexane/EtOAc 30/70) as a red solid (15.0 mg, 95% chemical
yield).
2
⎛
⎜
⎝
⎞
⎟
⎠
⎛
⎜
⎝
⎞⎛
⎟⎜
⎞
Ar
A
F
ns
s
ϕ = ϕ
⎟
⎠
Rf (cyclohexane/EtOAc 3/7) = 0.55. 1H NMR (300 MHz, CDCl3):
δ (ppm) 8.33 (s, 1H), 8.19 (d, J = 8.7 Hz, 1H), 7.96 (d, J = 7.5 Hz, 1H),
7.40 (dd, J = 7.5, 8.7 Hz, 1H), 2.83 (m, 2H), 1.76 (quint, J = 7.5 Hz,
2H), 1.28−1.23 (m, 18H), 0.88 (t, J = 6.9 Hz, 3H). 13C NMR (75
MHz, CDCl3): δ (ppm) 155.2, 151.5, 142.3, 130.5, 126.7, 123.9, 120.5,
119.0, 32.1, 29.84, 29.81, 29.8, 29.7, 29.5, 29.4, 29.3, 28.7, 25.6, 22.8,
14.3. MS (ESI+) m/z (%): 744.0591 (24) [M + Na]+, 393.2955 (100).
HRMS (ESI+): calcd for C23H29BrN5NaO3ReS 744.0606, found
744.0591. HPLC (40 to 100% ACN in 30 min, column C18A): rt
22.14 (>95%). IR: νmax/cm−1 2050, 2036, 1957, 1937, 1925, 1903
(CO).
X-ray Diffraction. X-ray crystallography was provided by the
ICMMO in Orsay. Data were collected by using a Kappa X8 APPEX II
Bruker diffractometer with graphite-monochromated Mo Kα radiation
(λ = 0.71073 Å). Crystals were mounted on a CryoLoop (Hampton
Research) with Paratone-N (Hampton Research) as cryoprotectant
and then flash-frozen under a nitrogen gas stream at 100 K. The
temperature of the crystal was maintained at the selected value (100 K)
by means of a 700 series Cryostream cooling device to within an
accuracy of 1 K. The data were corrected for Lorentz−polarization
and absorption effects. The structures were solved by direct methods
using SHELXS-9717a and refined against F2 by full-matrix least-squares
techniques using SHELXL-9717b with anisotropic displacement
parameters for all non-hydrogen atoms. Hydrogen atoms were located
on a difference Fourier map and introduced into the calculations as a
riding model with isotropic thermal parameters. All calculations were
performed by using the Crystal Structure crystallographic software
package WINGX.17c
After complex Re-Taquin-C4OH-Br (F) was dissolved in chloro-
form, yellow crystals suitable for X-ray diffraction were obtained upon
slow evaporation of the solvent.
CCDC 983687 contains supplementary crystallographic data for this
paper. These data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/
Community/Requestastructure.
Crystal data: formula C18H16BrN4O4Re; molecular weight Mr =
621.48; monoclinic, space group P21/n; a = 7.3351(3) Å; b =
13.5173(7) Å; c = 19.1874(9) Å; α = 90.00°; β = 90.8520(10)°; γ =
90.00°; V = 1902.23 Å3; T = 100(1) K; Z = 4; Z′ = 0; μ(Mo Kα) =
8.522 mm−1; 32913 reflections measured; 8302 unique data; 6832
reflections with I > 22σ(I), R(I > 2σ(I)) = 0.0555.
s
r
n 2
F
s ⎠⎝
r
r
where the subscripts s and r refer to the sample and the standard
reference solution, respectively, n is the refractive index of the solvents,
F is the integrated emission intensity, A is the absorbance at the
excitation wavelength (A < 0.1), and ϕ is the luminescence quantum
yield. Quinine sulfate in 0.1 N sulfuric acid was used as the standard
with a known emission quantum yield of 0.546 (λex 330−350 nm).
Conductivity Measurements. Measurements were performed
with a CDM210 conductivity meter (Meter Lab, Radiometer
Copenhagen). The cell was calibrated using a 0.1 M aqueous KCl
solution with a conductance of 11.97 mS cm−1 at 21 °C. Solutions of
compounds of interest were prepared at 10 μM in a H2O/DMSO 95/5
mixture.
Computations. The calculations were performed using the
Gaussian 09 program package. Geometries of all complexes were
optimized for the singlet and triplet states with the DFT method using
the hybrid B3LYP functional (unrestricted open-shell UB3LYP version
for triplet states) and the 6-311G** basis set for all atoms except
rhenium, for which the LANL2DZ basis set was used. Vibrational
harmonic frequency analysis of the optimized geometries was used to
ensure that there were true local minima with no imaginary frequencies.
The intensities of the 6 and 30 lowest-energy electronic transitions
were calculated using the TD-DFT method with the UB3LYP
functional, and the solvent effect was simulated using the polarizable
continuum model (PCM) for water.
Cell Culture. MDA-MB-231 breast cancer cells obtained from the
Human Tumour Cell Bank were used for the experiments. Cells were
maintained in monolayer culture in DMEM (Dulbecco’s Modified
Eagle Medium) with phenol red/Glutamax I, supplemented with 9% of
decomplemented fetal calf serum and 0.9% kanamycine, at 37 °C in a
5% CO2 air humidified incubator. Both control and treated cells were
processed in a similar way. They were seeded on glass slides (deposited
in 35 × 10 mm Petri dishes) in order to reach confluency after 48 h at
37 °C under an atmosphere of 95% air/5% CO2. The medium was
removed, and fresh growth medium (1.5 mL of DMEM without phenol
red and supplemented as previously described) was added to each flask
of control cells. In the case of treated cells, 1.5 mL of a solution of a
given compound in fresh growth medium (10 or 25 μM prepared from
a 5 × 10−3 M stock solution in DMSO) was added. The cells were
incubated at 37 °C under an atmosphere of 95% air/5% CO2 for 1 h.
The medium was then removed, and the cells were washed twice with
G
dx.doi.org/10.1021/ic5007007 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
a
Scheme 1. Synthesis of Taquinox and Taquin Complexes
a
Legend: (i) NaN3, DMF/H2O, 85 °C, 3 days; (ii) alkyne, (CuOTf)2.C6H6, toluene, 100 or 110 °C; (iii) aqueous NaOH, acetone, 50 °C, 16 h; (iv)
Re(CO)5Br, toluene, 110 °C.
a
phosphate buffered saline (Dulbecco’s PBS (D-PBS), 1X, 2 mL). Cells
were fixed by 4% paraformaldehyde (PFA; 1.5 mL) for 8 min at room
temperature and washed once with D-PBS (1X, 2 mL) and once with
pure water (2 mL). Slides were mounted using Vectashield solution
(H-1000, Vector Laboratories) just after the last water washing.
Fluorescence Imaging and Relative Cellular Uptake. In-cell
fluorescence imaging was performed using an IX71 (Olympus)
microscope equipped with a CCD (charged-coupled device, C-9100-
02, Hamamatsu Corp., Sewickley, PA) and ×60 (Plan Apo, NA 1.42)
objective. Compounds were detected using an appropriate filter set
(excitation D350/50x; beam splitter 400DCLP; emission HQ560/
80m; Chroma Technology) and excited using a Hg lamp (100 W)
attenuated by a neutral density filter (ND-1). Microscope settings and
functions were controlled using Simple PCI software (Hamamatsu).
Image analysis was performed using ImageJ Software and Simple PCI
software. For each image, the mean perinuclear luminescence intensity
per cell corrected for the background was determined (using ImageJ
software). For each condition (10 or 25 μM), average values and error
bars were calculated over a number of cells indicated directly below the
corresponding histogram in Figure 17 (right).
Scheme 2. Synthesis of Quinta Complexes
a
Legend: (i) 2-methylbut-3-yn-2-ol, Pd(PPh3)2Cl2, CuI, Et2NH, 40
°C, 30 min; (ii) NaOH (0.1 equiv), toluene, reflux, 1 h; (iii) azide
derivative, CuSO4·5H2O, sodium ascorbate, tBuOH/H2O, 110 °C;
(iv) Re(CO)5Br, toluene, 110 °C.
RESULTS AND DISCUSSION
references8,18 can be found that describe compounds incorpo-
rating respectively the 1-(quinolin-2-yl)-1,2,3-triazol-4-yl ligand
(Taquinox) and the 1-(quinolin-2-yl)-1,2,3-triazol-4-yl ligand
(Taquin) (Figure 1). Moreover, no metal complex prepared
from Taquin or Taquinox has been described and only very few
complexes of Ru(II), Pd(II), or Pt(II) incorporating the Tapy
ligand have been reported in the literature.19 The coordination
properties of these ligands have thus been overlooked, and the
present paper describes, to the best of our knowledge, the first
rhenium tricarbonyl complexes incorporating such ligands in
their coordination sphere.
We first synthesized quinoxaline- and quinoline-based
complexes bearing various side chains. The synthesis was
performed in three steps from the 2-chloro heterocycle
derivatives (Scheme 1). Reaction of the starting materials with
sodium azide in a refluxing mixture of DMF and water afforded
in good yields the 2-azido derivatives, which exist in equilibrium
with the tetrazolo derivatives 1 and 2, as discussed by
Chattopadhyay et al.8 These unsubstituted tetrazoles are
■
Design and Synthesis of New Rhenium Complexes.
We investigated the impact of structural modifications of the
bidentate ligand coordinating the rhenium(I) ion on the
luminescent properties of the complexes. We first focused on
modifications of the Pyta ligand and its extended version
containing a quinoline ring instead of a pyridine thereafter
named Quinta. We investigated the influence of inverting the
bridge between the heterocycle and the triazole ring. In the
parent Pyta and Quinta series, the triazole ring is formed by
reaction between the alkyne-functionalized heterocycle and an
azido side chain. We synthesized here a series of ligands in which
the triazole ring is linked to the heterocycle (pyridine, quinoline,
or quinoxaline) by a nitrogen atom (Figure 1) and systemati-
cally compared the physicochemical properties of the Re(CO)3
associated complexes with those of the corresponding parent
compounds.
Unlike the Tapy ligand (1-(2-pyridyl)-1,2,3-triazole), which
has been quite documented in the literature, very few
H
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a
Scheme 3. Synthesis of Tapy Complexes
a
Legend: (i) diphenylphosphoryl azide (DPPA), pyridine, 120 °C, 24 h; (ii) alkyne, (CuOTf)2·C6H6, toluene, 110 °C; (iii) Re(CO)5Br, toluene, 110
°C.
a
hydrophobic character on the optical properties, as already
described for other rhenium tricarbonyl complexes.20
Scheme 4. Synthesis of Tapy Complex L
To assess the influence of the inversion of the triazole link to
the heterocycle, two rhenium complexes of the Quinta series
have been synthesized bearing either a side chain terminated by
the primary alcohol (F) or a 12-carbon alkyl chain (G) (Scheme
2). 2-Ethynylquinoline (10) was prepared from 2-chloroquino-
line by a Sonogashira coupling with 2-methylbut-3-yn-2-ol in the
presence of CuI and bis(triphenylphosphine)palladium(II)
dichloride followed by treatment with a catalytic amount of
solid NaOH in refluxing toluene.9 The Quinta ligands 11 and 12
were then prepared by CuAAC “click” reactions under classical
conditions (Scheme 2) with azidohexanol14a or dodecyl azide14b
previously prepared according to described procedures. The
complexes F and G were finally formed after reaction with
rhenium pentacarbonyl bromide as above.
A series of four pyridine-based ligands (Tapy derivatives)
bearing either a butanol or an aliphatic side chain of variable
length (R = −CnH2n+1, n = 4, 8, 12) and their corresponding
rhenium complexes H−K were synthesized using the same
strategy from the tetrazolopyridine 13 (Scheme 3). This
intermediate was prepared in high yield by treatment of
pyridine N-oxide by diphenylphosphoryl azide in pyridine at 120
°C for 24 h.
All of the Re(I) tricarbonyl complexes described at this stage
were synthesized using the rhenium pentacarbonyl bromide
precursor and thus have a bromide as ligand. In order to study
the potential influence of this halide ligand and to compare their
properties with those of Re-Pyta-C12-Cl described elsewhere,20b
we prepared complex L bearing a chloride ligand instead of a
bromide (Scheme 4). Complex L was prepared from ligand 17
by reaction with rhenium pentacarbonyl chloride in toluene at
110 °C.
a
Legend: (i) Re(CO)5Cl, toluene, 110 °C.
expected to predominantly exist in the closed form.8 With this
kind of pyridotetrazole derivative, Cu-catalyzed azide alkyne
cycloadditions (CuAAC) are generally unsuccessful under
standard conditions. Therefore, to perform the desired click
reactions between the quinoxalino- and quinolinotetrazoles 1
and 2 and various alkynes, we applied a previously reported
procedure using Cu(I) trifluoromethanesulfonate benzene
complex as a catalyst in toluene.8 Reactions were performed
in a sealed tube under an inert atmosphere to avoid oxidation of
the catalyst, and heating appeared necessary for the reactions to
proceed. All of the alkynes used were commercially available
except for methyl hex-5-ynoate, necessary to prepare ligand 5,
which was synthesized in two steps from hexyn-1-ol by Jones
oxidation followed by esterification.12 Ligand 5 was quantita-
tively hydrolyzed under basic conditions to afford 6 prior to
rhenium coordination. Coordination of the ligands 3, 4, and 6−
8 with rhenium was achieved by reaction with rhenium
pentacarbonyl bromide in refluxing toluene to afford complexes
A−E in good yields (Scheme 1).
Butanol and butanoic side chains were chosen, as they enable
further chemical modifications of the terminal functional group
or grafting of the ligand on other moieties of interest. We also
introduced aliphatic side chains of different lengths in order to
investigate the impact of increasing alkyl chain length and
a
Scheme 5. Synthesis of BTDTa Complexes
a
Legend: (i) Br2, HBr 33%, AcOH; (ii) TMSA, CuI, Pd(PPh3)2Cl2, Et3N/DMF; (iii) K2CO3, MeOH; (iv) azide, CuSO4·5H2O, sodium ascorbate,
tBuOH/H2O; (v) Re(CO)5Br, toluene, 110 °C.
I
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a
Scheme 6. Synthesis of TaBTD Complex
a
Legend: (i) NaNO2, NaN3, aqueous HCl, (ii) tetradecyne, (CuOTf)2.C6H6, toluene, 110 °C; (iii) Re(CO)5Br, toluene.
Table 1. Nomenclature Used for the Complexes A−P
aromatic
a
complex
letter
ligand
side chain
−C8H17
−C4H8OH
X ligand
Re-Taquinox-C8-Br
Re-Taquin-C4OH-Br
A
B
C
Taquinox
Taquin
Br
Br
Br
Re-Taquin-C3COOH-
Br
Taquin
−C3H6COOH
Re-Taquin-C8-Br
Re-Taquin-C12-Br
Re-Quinta-C6OH-Br
Re-Quinta-C12-Br
Re-Tapy-C4OH-Br
Re-Tapy-C4-Br
D
E
F
Taquin
Taquin
Quinta
Quinta
Tapy
−C8H17
Br
Br
Br
Br
Br
Br
Br
Br
Cl
Cl
Br
Br
Br
−C12H25
−C6H12OH
−C12H25
−C4H8OH
−C4H9
G
H
I
Tapy
Re-Tapy-C8-Br
J
Tapy
−C8H17
Re-Tapy-C12-Br
K
L
Tapy
−C12H25
−C12H25
−C12H25
−C6H12OH
−C12H25
−C12H25
Re-Tapy-C12-Cl
Tapy
Re-Pyta-C12-Cl19b
Re-BTDTa-C6OH-Br
Re-BTDTa-C12-Br
Re-TaBTD-C12-Br
M
N
O
P
Pyta
Figure 3. Absorption spectra of complexes A, D, and J in acetonitrile
(10 μM).
BTDTa
BTDTa
TaBTD
a
See Figure 1.
4-(4-R-1H-1,2,3-triazol-1-yl)benzo[c][1,2,5]thiadiazole
(TaBTD) containing Re(CO)3 complexes were prepared. The
synthesis of BTDTa complexes N and O was performed in five
steps (Scheme 5). Monobrominated benzothiadiazole 18 was
obtained in poor yield from the commercially available
We extended the series of rhenium complexes with
benzothiadiazole−triazole-based compounds.21 Both 4-(1-R-
1H-1,2,3-triazol-4-yl)benzo[c][1,2,5]thiadiazole (BTDTa) and
Figure 2. ORTEP drawing of Re-Taquin-C4OH-Br (F) (30% probability level).
J
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Table 2. Photophysical Data for the Complexes at Room Temperature in Acetonitrile
a
complex
letter
excitation (nm)
emission (nm)
range (nm)
yield (%)
SD
Re-Taquinox-C8-Br
Re-Taquin-C4OH-Br
Re-Taquin-C3COOH-Br
Re-Taquin-C8-Br
Re-Taquin-C12-Br
Re-Quinta-C6OH-Br
Re-Quinta-C12-Br
Re-Tapy-C4OH-Br
Re-Tapy-C4-Br
A
B
C
D
E
F
380
380
380
380
617
617
617
617
515−700
515−700
515−700
515−700
0.05
0.06
0.06
0.06
0.01
0.01
0.004
0.01
G
H
I
360
360
360
360
360
332
365
365
355
564
564
564
564
569
522
470
470
455
485−695
480−695
480−695
480−695
485−695
440−650
400−560
400−560
395−560
0.15
0.16
0.17
0.17
0.19
0.10
0.53
0.51
0.99
0.01
0.008
0.015
0.008
0.009
0.04
0.06
0.1
Re-Tapy-C8-Br
J
Re-Tapy-C12-Br
K
L
Re-Tapy-C12-Cl
Re-PyTa-C12-Cl19b
Re-BTDTa-C6OH-Br
Re-BTDTa-C12-Br
Re-TaBTD-C12-Br
M
N
O
P
0.09
a
Determined relative to quinine sulfate (Φ = 54.6%) in 0.1 N H2SO4 as a standard. Differences in the refractive indices of the solvent systems were
accounted for.
Figure 4. Absorption spectra of complexes F and G (left) and Re-Pyta-C12-Cl (M) (right) in acetonitrile (10 μM).
Figure 5. Absorption spectra of complexes E and G (left) and of complexes K and M (right) in acetonitrile (10 μM).
benzothiadiazole. Under the conditions used, the derivative
dibrominated at positions 4 and 8 was mainly formed.
Sonogashira coupling with (trimethylsilyl)acetylene (TMSA)
followed by TMS deprotection under basic conditions afforded
compound 19 in 34% yield over two steps. The ligands 20 and
21 were then prepared in good yields by CuAAC “click”
K
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angles are in the 88.7−95.2° range. The trans bond angles are
respectively 165.7(2), 172.7(2), and 175.1(2)°, showing a
moderate distortion in the octahedral geometry. The N(1)−
Re(1)−N(3) angle has a value of 73.3(2)°, comparable to that
found for Pyta-based Re complexes5f and reflecting the
constrained five-membered coordination ring. Finally, the
Taquin ligand in the Re−tricarbonyl complex is close to planar,
with an angle between the planes defined by the two aromatic
heterocycles (quinolinyl and triazolyl) of 5.92°.
Optical Properties of the Rhenium Complexes. We
investigated the UV−vis and luminescence properties of the
synthesized complexes. We first recorded spectra in acetonitrile
at 10 μM concentrations. Rhenium complex A shows a
structured band with two peaks around 345 and 355 nm and
a broad band centered at 425 nm (Figure 3). The Taquin
complexes B−E exhibit similar features with a blue shift: two
peaks around 323 and 333 nm and a broad band centered at 380
nm (Figure 3, with D as a typical trend, and Table 2).
Figure 6. Absorption spectra of complexes N−P in acetonitrile (10
μM).
Quinta complexes F and G in acetonitrile exhibit a band
centered at 338 nm and a shoulder around 375 nm that most
likely have a significant metal to ligand charge transfer (MLCT)
character. Re-Pyta-C12-Cl (M) shows a band centered at 288
nm (π → π* intraligand transition) and a lower-energy band at
332 nm with MLCT character (Figure 4).5c,d
reactions with azidohexanol or dodecyl azide as mentioned
above. The complexes N and O were finally formed after
reaction with rhenium pentacarbonyl bromide.
Finally, the TaBTD complex P bearing a long C12 alkyl chain
was synthesized using the same procedure used for the other
inverted-bridge ligands described above, as shown in Scheme 6.
The starting 4-azidobenzothiadiazole 22 was prepared from 4-
aminobenzothiadiazole under classical azidation conditions.
For the sake of clarity in the following discussion, a systematic
nomenclature will be used for the Re complexes as follows: Re-
aromatic ligand-side chain-X ligand. All of the complexes
described and studied here are summarized with their systematic
names in Table 1.
Crystallography. We obtained crystals of the complex Re-
Taquin-C4OH-Br (F) from chloroform solution under ambient
conditions and performed X-ray analysis (Figure 2). The
complex crystallizes in space group P21/n. The rhenium ion
displays a distorted-octahedral coordination geometry. The
bond lengths and angles are found in a range comparable to
those for rhenium tricarbonyl complexes based on Pyta ancillary
ligands (Supporting Information, Table S1).5f The rhenium
atom is coordinated to two nitrogens of the Taquin ligand, one
bromine atom, and three carbonyl groups in a fac geometry. The
average Re−carbon bond length is 1.96 Å, and the OC−Re−CO
Complexes of the Tapy series H−L with a bromide or
chloride as ligand show a band at 270 nm assigned to a π → π*
intraligand transition by analogy with Pyta complexes and a
lower-energy band centered at 360 nm with MLCT character
(Figure 3, exemplified by J, and Table 2). For the four series
Quinta, TaQuin, Pyta, and Tapy described so far, the complexes
of a same series have the same absorption profile in acetonitrile
(organic solvent) whatever the nature of the appended side
chain, as already pointed out in previous studies for comparable
complexes.20b,c A significant impact of the small structural
modification of inverting the bridge between the triazole ring
and the heterocycle can be seen in the pyridine and quinoline
series: in both pyridine and quinoline series, inverting the
triazole bridge decreases the energy of the MLCT band: i.e.,
leads to a shift toward higher wavelengths (Figure 5). Finally,
going from Tapy to Taquin to Taquinox ligand (Figure 3), i.e.
extending the aromatic surface and/or the electron-deficient
character of the heterocycle, leads also, as expected, to a
bathochromic shift of the lowest-energy band.
Figure 7. Absorption spectra of complexes F, G, and M (left) and of complexes A, D, and J (right) in H2O/DMSO 98/2 (10 μM).
L
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Figure 8. Absorption spectra of complexes E and G (left) and of complexes K and M (right) in H2O/DMSO 98/2 (10 μM).
(Figure 6): a structured peak at 324 nm, a shoulder at 365 nm
with a MLCT character, and a broad absorption band centered
at 420 nm. Going to the TaBTD series (from O to P) results
only in slight changes in the absorption profile. The complex P
exhibits a peak around 330 nm, a weak MLCT band at 355 nm,
which is slightly blue-shifted in comparison to that for complex
O, and a broad band at 435 nm.
We performed similar studies in aqueous solutions containing
2% DMSO, a better match for further biological studies. The
absorption profiles of the Quinta complexes and of the Pyta
complex are again comparable to those previously reported in
the literature.5b,6 Complexes F and G exhibit a band centered at
335 nm that most likely has a significant metal to ligand charge
transfer (MLCT) character. Complex M shows a MLCT band
centered at 340 nm (Figure 7, left).
Rhenium complex A shows a structured band with two peaks
around 350 and 360 nm and a broad band centered at around
440 nm of undefined character. Under aqueous conditions,
whereas the Taquin complexes B−E have similar absorption
profiles, a strong impact of the side chain on the absorption
maxima is observed. The complexes of the Tapy series H−K
Figure 9. Absorption spectra of complexes N−P in H2O/DMSO 98/2
(10 μM).
In the benzo[c][1,2,5]thiadiazole (BTD) series N−P,
absorption profiles of complexes N and O show similar features
Table 3. Photophysical Data for Complexes A−P at Room Temperature in a 98/2 H2O/DMSO Mixture
a
complex
letter
excitation (nm)
emission (nm)
range (nm)
yield (%)
SD
Re-Taquinox-C8-Br
Re-Taquin-C4OH-Br
Re-Taquin-C3COOH-Br
Re-Taquin-C8-Br
Re-Taquin-C12-Br
Re-Quinta-C6OH-Br
Re-Quinta-C12-Br
Re-Tapy-C4OH-Br
Re-Tapy-C4-Br
A
B
C
D
E
F
360
375
375
385
385
335
335
350
350
375
380
370
340
340
648
610
610
597
593
575
582
560
560
554
554
554
512
495
555−790
515−750
515−750
515−750
515−750
500−745
500−730
476−695
470−690
470−690
470−690
470−690
440−650
425−580
0.08
0.26
0.23
1.14
1.30
0.21
0.56
0.99
0.80
3.39
3.20
3.56
0.75
0.05
0.01
0.02
0.05
0.18
0.19
0.02
0.08
0.46
0.33
0.29
0.57
0.22
0.12
0.02
G
H
I
Re-Tapy-C8-Br
J
Re-Tapy-C12-Br
K
L
Re-Tapy-C12-Cl
Re-Pyta-C12-Cl
M
N
O
P
Re-BTDTa-C6OH-Br
Re-BTDTa-C12-Br
Re-TaBTD-C12-Br
a
Determined relative to quinine sulfate (Φ = 54.6%) in 0.1 N H2SO4 as a standard. Differences in the refractive indices of the solvent systems were
accounted for.
M
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Figure 10. Luminescence emission spectra of Tapy complexes H−K (10 μM) in acetonitrile (left) and in H2O/DMSO 98/2 (right) (λexc 370 nm).
share the same behavior, and this will be discussed in more detail
below. Complexes A, D, and J bearing the same C8 side chain
are thus compared. Complex D exhibits a structured band
around 330 and 340 nm and a broad band centered at 380 nm.
Tapy complex J shows a band at 290 nm assigned to a π → π*
intraligand transition by analogy with Pyta complexes and a
lower-energy band centered at 380 nm with MLCT character
(Figure 7, right). A significant impact of the bridge inversion is
also evidenced in aqueous solution for the pyridine and
quinoline series, and the same modifications in the absorption
profiles as in acetonitrile can be observed (Figure 8). In aqueous
solution, in the Tapy series, substituting the bromide ligand by a
chloride (complex K to L) leads to a 10 nm blue shift of the
MLCT band (from 380 to 370 nm), in contrast to what is
observed in organic solvent.
In the BTD series, the BTDTa-based complexes N and O
show a peak centered around 330 nm and a broad band around
415 nm (Figure 9, Table 3). In contrast to the case for
acetonitrile and to the other series described in water, the
absorption profiles do not significantly change upon mod-
ification of the side chain under aqueous conditions. Going to
the TaBTD series (from O to P) results in deep changes in the
absorption intensity. The complex P exhibits a peak around 330
nm with an ill-defined shoulder around 378 nm. A broad band is
also observed centered at 450 nm, blue-shifted by 35 nm in
comparison to complex O, a shift comparable with those
observed for the other series (Figure 9, Table 3).
We then studied the emission properties of the rhenium
complexes A−P at 10 μM both in acetonitrile and in a water/
DMSO 98/2 mixture. Taquinox complex A appears to be
nonemissive in acetonitrile upon photoexcitation at either 355
or 425 nm. Upon photoexcitation (λexc 380 nm), Taquin
complexes B−E display broad emission bands centered at 617
nm of similar low intensities, whatever the nature of the side
chain (Table 2). In comparison, the Quinta complexes F and G
are essentially non emissive in acetonitrile. The Tapy complexes
H−K display a broad emission band at 564 nm. Complex L,
bearing a chloride ligand instead of a bromide, has a maximum
emission at 569 nm. The Pyta complex M shows a typical broad
emission band at 522 nm, in total agreement with data already
reported for this complex or others of the family.6 Inversion of
the bridge between the triazole ring and the pyridine in the
ligand induces a red shift of approximately 30−35 nm in the
emission of their corresponding rhenium tricarbonyl complexes,
while their Stokes shift remains high (190−205 nm). In all cases,
3
the emissions most likely originate from a triplet MLCT state
as for related rhenium tricarbonyl complexes.
When the Pyta/Quinta and Tapy/Taquin series are
compared, a red shift is observed in the emission of the
quinoline-based complexes relative to the pyridine complexes,
which fits previous records. Table 2 summarizes photophysical
data for rhenium complexes A−P in acetonitrile along with the
determined quantum yield values. In acetonitrile, the quantum
yields obtained within a series are closely similar, whatever the
nature of the appended side chain. Quantum yields for the
quinoline-containing complexes B−G are dramatically low with
a mean value of 0.06%. The Tapy complexes H−L have
quantum yield values between 0.15 and 0.19%, slightly higher
than the values for the Pyta complexes.
Surprisingly, BTD-based complexes N−P show narrower
emission bands with higher intensities centered at 470 nm for N
and O and 455 nm for P. The TaBTD series is characterized by
a blue shift in emission in comparison with the BTDTa
complexes, which is in opposition to the pyridine and quinoline
families. Complexes N−P display also interesting quantum yield
values in acetonitrile of 0.53, 0.51, and 0.99%, respectively, and
may thus constitute a promising class of new rhenium probes in
organic media.
The same experiments were then performed at the same
concentration in water (2% DMSO). Upon photoexcitation at
360 nm, Taquinox complex A displays a low-intensity emission
band at 647 nm. For the quinoline and pyridine families, trends
similar to those in acetonitrile can be observed for the shifts in
the maximum emission wavelengths. However, deep changes in
emission intensities are observed in aqueous medium depending
on the nature of the side chain for the Taquin and Tapy
complexes. This behavior, which was already reported for Re-
Pyta complexes with alkyl side chains of increasing length and
for cationic rhenium complexes with a 2,2′-bipyridine and a
lipophilic derivative of hydroxymethylpyridine as ligands,20b,c
will be discussed in more detail below. The Taquin complexes
B−E display broad emission bands between 593 and 610 nm
depending on the side chain (vide infra). These bands are blue-
shifted in comparison with the emission of quinoxaline
derivative A and slightly red-shifted in comparison to the
Quinta analogues F and G, which show maximum emissions at
N
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1
Figure 11. Stacked H NMR spectra of complexes M, L, and K (c ≈ 5.0 mg/mL) and ligand 17 in d6-DMSO after 4 days.
575 and 582 nm, respectively, close to published values for
similar complexes.5b The Tapy complexes H−L display a broad
emission band at 560 or 554 nm depending on the side chain
(vide infra). The Pyta complex M shows a typical broad
emission band at 512 nm, in total agreement with data already
reported for this complex or other closely related species.7
Inversion of the bridge between the triazole ring and the
pyridine in the ligand induces a bathochromic shift of
approximately 45−50 nm in the emission of their corresponding
rhenium tricarbonyl complexes. In all cases again, the emissions
3
most likely originate from a triplet MLCT state as for related
rhenium tricarbonyl complexes.5d−f,6 When the Pyta/Quinta
and Tapy/Taquin series are compared, a red shift is observed in
the emission of the quinoline-based complexes relative to the
O
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Figure 12. Frontier orbital diagram for Re-Pyta-C2-Br.
Figure 13. Frontier orbital diagram for Re-Tapy-C2-Br.
pyridine complexes, which fits previous records and fits those
observed in organic solvent. Surprisingly, BTD-based complexes
N−P are overall nonemissive, whatever the excitation wave-
length in aqueous solution.
A direct comparison of complex E with G and L with M
highlights the huge impact of the bridge inversion alone on the
photophysical properties of rhenium tricarbonyl complexes
bearing long alkyl chains in aqueous medium. Quantum yield
values of 0.56% and 0.75% are found for Re-Quinta-C12-Br (G)
and Re-Pyta-C12-Cl (M), respectively, which matches values for
complexes of similar structures under comparable conditions.5b
The Taquin analogue E shows a quantum yield value of 1.30%,
while the Tapy derivative L has a quantum yield of 3.56%, which
represents roughly 2-fold and 4-fold increases, respectively
P
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Figure 14. Spin density plots of the optimized triplet states for Re-Pyta-
Br (A) and Re-Tapy-Br (B).
Figure 16. MDA-MB-231 cells (scale bars 20 μm). Luminescence
signal for cells incubated at 25 μM at 37 °C for 1 h with (a) Re-Pyta-
C12-Cl (M) and (b) Re-Tapy-C12-Cl (L). The same illumination and
recording parameters were used for both images, but image (a) is
presented with enhanced brightness/contrast conditions in order to see
the cells. The intensity profiles shown in Figure 17 are measured along
the white arrow for each image. All cells were fixed, and slides were
mounted.
(Table 3). The results obtained for the Tapy complexes bearing
long alkyl chains J−L are particularly interesting and, to the best
of our knowledge, unprecedented for Re tricarbonyl complexes
in aqueous medium. It is striking to obtain such an enhancement
in the photophysical properties with such a small difference in
the chemical structure of the complexes. From this point on, we
focus on the complexes of the Tapy series, as this series displays
by far the most interesting properties. We performed further
studies in an attempt to rationalize our observations and
determine whether the peculiar behavior revealed originates
from intrinsic electronic properties of the Tapy core in the
coordination sphere of the rhenium or from a particular
conformational or aggregation state of the Re-Tapy complexes
in aqueous solution.
Side Chain Effect and Luminescence Modulation. As
stated above, modifications in the side chain cause profound
changes in the emission intensities of the complexes of Taquin
and Tapy series in aqueous solution in comparison to
acetonitrile. We studied this behavior for the Tapy series in
more detail, and results are presented thereafter.
In organic solvent, the photophysical properties of the
complexes are identical (λexc, λem, Φ) (Figure 10, left). In
aqueous solution, a small blue shift (6 nm) is observed in the
maximum emission wavelength for the longer alkyl chain
derivatives J and K (Figure 10, right). The quantum yields
values of all complexes H−K increase from acetonitrile to water,
but more importantly, the complexes J and K bearing long alkyl
chains (from C8) show an impressive enhancement in emission
and quantum yield (Figure 10 and Table 3) in water in
comparison to H and I. This behavior was already reported for
Pyta-based or 2,2′-bipyridine-based rhenium tricarbonyl com-
plexes.20 This effect of the side chains can be explained by a
chain wrapping or fold back onto the luminescent Re core. In
aqueous solution, the complex adopts a conformation driven by
hydrophobic forces in which the alkyl chain wraps around the
Re core and enhances its emission properties by isolating it from
the solvent environment. As a result, the excited state is shielded
from solvent quenching effect. This hypothesis is further
supported by the results obtained from temperature studies20b,c
(see the Supporting Information).
However, this side chain effect is not sufficient to explain the
luminescence enhancement of the Tapy series in comparison to
Pyta complexes. A strong emission enhancement is indeed
observed for Tapy complexes for all of the side chains used. It is
well exemplified by the fact that complex I shows a stronger
emission in water than in acetonitrile, whereas the emission of
the corresponding Pyta complex is totally quenched in aqueous
medium.20b Tapy-based rhenium tricarbonyl complexes are thus
intrinsically more luminescent than the corresponding Pyta
complexes in both organic and aqueous media.
Pyta and Tapy complexes with C12 side chains and halides as
ligands show the same solubility range as determined by UV
titration experiments: 7.0 μM for complexes Re-Tapy-C12-Br
Figure 15. Absorption spectra (10 μM in H2O/DMSO 98/2, 25 °C) and TD-DFT predicted transitions (vertical lines) for Re-Pyta-C12-Cl (M) (left)
and Re-Tapy-C12-Br (K) (right).
Q
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Figure 17. (left) Intensity profiles collected along the white arrow for each case in Figure 16 (performed with ImageJ software). The same illumination
and recording parameters were used for both profiles. Cells were incubated at 25 μM at 37 °C for 1 h with Re-Pyta-C12-Cl (M; image a, red trace) and
Re-Tapy-C12-Cl (L; image b, black trace). (right) Average of the mean perinuclear luminescence for collections of MDA-MB-231 control cells and
cells incubated for 1 h at 37 °C at 10 μM (white bars) or 25 μM (dashed bars). For each condition the number of cells used is specified. Luminescence
signals were monitored using the same filter set (see the Experimental Section) and the same conditions of acquisition. The mean perinuclear
luminescence was corrected for the background before averaging. The standard error was calculated with a Student coefficient for a two-sided
confidence interval of 95% and for the number of cells of the collection.
1
(K) and Re-Tapy-C12-Cl (L) and 6.0 μM for Re-Pyta-C12-Cl
(M) in a H2O/DMSO 98/2 mixture. This is indicative of a
similar state in aqueous solutions at identical concentrations,
and therefore a different aggregation state could not account for
the difference in luminescence intensity observed.
which shows only one set of signals in H NMR (Figure 11).
However, a slow and partial dissociation of approximately 30% is
evidenced for Tapy complexes K and L under the same
conditions (no dissociation is observed over 20 h). Two sets of
signals in the 1H spectra are indeed visible corresponding to the
rhenium complex and to the ligand alone, as highlighted in
Figure 11 in the stacked spectra. An equilibrium between
coordinated and uncoordinated ligand is slowly established as
the percentage of dissociation reaches a maximum between 36
and 40% and does not increase any more. The decoordination of
rhenium could arise from a stronger destabilization of the halide
ligand by the trans effect of the carbonyl ligand in the Tapy
complexes in comparison with the Pyta complexes. The higher
stability of the Pyta complex under these conditions is also in
agreement with a higher electron density on the N(3) of the
triazole in comparison with the coordinating N(2) in the Tapy
Ligand Exchange and Stability: Conductivity and NMR
Studies. To further compare the Pyta and Tapy complexes, we
explored their stability and potential ligand exchange in polar
coordinating solvents. It has indeed been described by means of
conductivity measurements that the bromide ligand in other
Pyta and Quinta complexes is immediately exchanged for water
under aqueous conditions.5b,22 We therefore performed
conductivity measurements of 10 μM solutions of complexes
Re-Tapy-C12-Br (K), Re-Tapy-C12-Cl (L), and Re-Pyta-C12-
Cl (M) in 5% DMSO/H2O to investigate this halide ligand
exchange. The conductivity measurements were performed over
a 24 h period and compared with identical concentrations of
NaCl (10.88 μS cm−1) and CaCl2 (23.63 μS cm−1) in the same
solvent mixture. In all cases, over 24 h, the rhenium complexes
exhibit stable conductivity values lower than that of the 1/1
electrolyte (4.77, 3.04, and 2.98 μS cm−1 for Re-Tapy-C12-Br
(K), Re-Tapy-C12-Cl (L), and Re-Pyta-C12-Cl (M), respec-
tively). This reflects that no halide for H2O exchange occurs for
these three complexes at the low concentrations used.
ligand (Mulliken population analysis charges from DFT
̈
calculations (vide infra): Tapy complex, N(2) −0.166; Pyta
complex, N(3) −0.431).24 As a result of the partial
decoordination of the Tapy complexes in concentrated
DMSO solutions, solutions have to be freshly prepared
immediately before use for photophysical or biological studies.
Theoretical Studies. DFT calculations were performed to
compare the geometric and electronic structures of the Re-Pyta
and Re-Tapy complexes. The results obtained for Re-Pyta are
consistent with the already reported calculations on other Re-
Pyta complexes bearing a halide or a water molecule in their
coordination sphere.5b,f We limited the alkyl chain length to an
ethyl group to reduce calculation time. We used the B3LYP
functional in combination with the LANL2DZ basis set for
rhenium and 6-311G** basis set for all other atoms.25
DMSO is often used as an additive in solutions for such
complexes to enable their solubility in aqueous media, and stock
solutions in DMSO are frequently used for biological experi-
ments. A fast ligand dissociation has been recently reported in
DMSO solutions of Ru(η6-arene)Cl2(L).23 We therefore
1
recorded H NMR spectra of complex M and complexes K
and L along with their ligand alone 17 in d6-DMSO (ca. 2.0 mg
in 0.4 mL) at different time intervals. The results obtained after
4 days at room temperature are shown in Figure 11.
This study highlights an interesting difference in the stability
of Pyta and Tapy complexes in these conditions. No ligand
dissociation is observed after 4 days for Re-Pyta-C12-Cl (M),
In the singlet optimized structures of Re-Pyta-Br and Re-
Tapy-Br, the Pyta and Tapy ligands were found to be planar.
The predicted Re−CO bond lengths are similar for both
complexes (1.917−1.935 Å). The Re−halide bonds are longer
than the Re−CO bonds, with predicted values of 2.678 and
R
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2.675 Å for Re−Br bonds in Re-Pyta and Re-Tapy, respectively.
The Re−Cl bonds in the corresponding complexes are slightly
shorter and are calculated to be 2.533 and 2.530 Å, respectively.
The distances Re−N(py) (2.241 vs 2.226 Å) and Re−N(ta)
(2.179 vs 2.168 Å) are slightly shorter in the Re-Tapy complex.
This could be due to the shorter length of the bond constituting
the bridge between the pyridine and the triazole ring in the Tapy
ligand (C−N bond 1.406 Å vs C−C bond 1.454 Å in the pyta
ligand). The dihedral angles between the ligand and the
Re(CO)2 equatorial unit are similar in both cases, with
calculated values of 9.4 and 10.4° for Re-Pyta and Re-Tapy,
respectively.
Frontier orbital diagrams are shown in Figures 12 and 13,
respectively. As already described for Re-Pyta complexes, the
HOMO-4 to HOMO levels are rhenium-based with partial
carbonyl character and a bromide component except for
HOMO-2.5b,f These features are similarly found in the Re-
Tapy complex, for which the only difference is a higher
contribution of the ligand in HOMO-3. In both cases, the
HOMO and HOMO-1 levels are close in energy. The HOMO
and HOMO-1 levels contain significant rhenium 5dxz and 5dyz
character, while the HOMO-2 level contains the 5dxy orbital.
The LUMO and LUMO+1 levels are mainly centered on the
aromatic ligand and particularly the π* antibonding orbital.
These results are fully consistent with previously published
studies on Re-Pyta complexes and show strong similarities in the
molecular orbital diagrams of Pyta- and Tapy-based complexes.
The Re-Tapy complex is characterized by orbitals of lower
energies and a smaller gap (2.88 eV vs 3.06 eV), which is in good
agreement with the values obtained experimentally by UV−vis
absorption (3.08 eV for K and 3.28 eV for M).
We calculated and compared the spin densities of the
optimized triplet electronic states of Re-Pyta and Re-Tapy
complexes. The spin density plots, shown in Figure 14, support
the MLCT character of the optimized triplet state. The spin
densities on rhenium are comparable for both complexes, but a
difference in their distribution on the ligands is observed. The
spin density is stronger on the pyridine ring in the Pyta ligand,
whereas it is more localized on the triazole ring in the Tapy
ligand. This difference in spin density distribution on the ligand
in the optimized triplet state could account for the variation in
the luminescence observed in the corresponding complexes.
We finally compared the nature of the electronic transitions
for Re-Pyta5b,f and Re-Tapy complexes using time-dependent
DFT calculations. The UB3LYP/LANL2DZ/6-311G** level
was used with a polarized continuum model for water. The
lowest-energy transitions are summarized in the Supporting
Information (6 for the Re-Pyta complex and 20 for the Re-Tapy
complex; Tables S3 and S4 in the Supporting Information,
respectively). The lowest energy transitions with significant
oscillator strength are shown along with the experimental
absorption spectra in Figure 15. The predicted lowest energy
transition for Re-Pyta-Br at 372 nm (f = 0.095) is a transition
from the metal-based HOMO-1 orbital to the LUMO
antibonding ligand-based orbital, thus constituting a MLCT
band. In the case of Re-Tapy-Br, similarly, the predicted lowest
energy transition at 404 nm (f = 0.1083) is a transition from a
combination of the metal-based HOMO and HOMO-1 orbitals
to the LUMO π* orbital and is also of MLCT character. The
two transitions at 310 nm (f = 0.0793) and 302 nm (f = 0.0788)
are from HOMO-3 and HOMO-4, respectively, to the LUMO
showing an additional intraligand transition character.
The theoretical calculations reproduce satisfactorily the
experimental data obtained by UV for both Re-Pyta and Re-
Tapy complexes. A variation in the spin density distribution on
the ligands is observed in the optimized triplet states, which
suggests a difference in the emissive state in Re-Pyta and Re-
Tapy complexes, respectively, that could account for the
variation in the luminescence observed.
Preliminary Cellular Imaging. We finally performed
preliminary cellular imaging studies in MDA-MB-231 breast
cancer cells and compared luminescence signals for Re-Tapy-
C12-Cl (L) and Re-Pyta-C12-Cl (M). The compounds were
incubated at 10 or 25 μM for 1 h; the cells were subsequently
fixed (PFA) and imaged after the slides were mounted. As
shown in Figure 16, both complexes show similar perinuclear
distributions, as already described for closely related complexes
under the same conditions.6,20b In contrast, the luminescence
intensity is tremendously enhanced in the case of Re-Tapy-C12-
Cl (L), as illustrated by the intensity profiles recorded along
cells presented in Figure 17 (left) or by the average intensity of
the mean perinuclear luminescence obtained for collections of
MDA-MB-231 cells incubated with complexes shown in Figure
17 (right). A difference in cellular uptake is unlikely, given the
high similarity in the chemical structure and hence lipophilicity
of both complexes. This luminescence enhancement can be
explained by the improved photophysical properties of the Re-
Tapy complexes as described above.
CONCLUSION
■
New rhenium tricarbonyl complexes prepared from different
bidentate aromatic ligands were developed. Complexes with
benzothiadiazole−triazole ligands show interesting luminescent
quantum yields in acetonitrile and may constitute valuable
luminescent metal complexes in organic media. A series of
complexes with bidentate 1-(2-quinolinyl)-1,2,3-triazole (Ta-
quin) and 1-(2-pyridyl)-1,2,3-triazole (Tapy) ligands bearing
various 4-substituted alkyl side chains has been designed and
synthesized with efficient procedures. Their photophysical
properties have been characterized in acetonitrile and in a
H2O/DMSO (98/2) mixture and compared with those of the
parent Quinta- and Pyta-based complexes. Tapy complexes
bearing long alkyl chains show impressive enhancement of their
luminescent properties in aqueous medium relative to the
parent Pyta complex. Stability studies in coordinating DMSO
highlight a partial decoordination in the case of the Tapy
complex. Theoretical calculations have been performed to
further characterize this new class of rhenium tricarbonyl.
Preliminary cellular imaging studies in MDA-MB231 breast
cancer cells reveal a strong increase in the luminescence signal in
cells incubated with the Tapy complex. We demonstrated how
tiny structural modifications can cause profound changes in the
photophysical properties of such metal complexes. Further
experiments are needed to rationalize this behavior. This study
nevertheless points out the potential of the Tapy ligand in
coordination chemistry, which has been so far underexploited.
ASSOCIATED CONTENT
■
S
* Supporting Information
Text, tables, a figure, and a CIF file giving crystallographic data
and refinement details and experimental bond lengths and
angles for complex F, predicted transitions, and temperature
studies. This material is available free of charge via the Internet
at http://pubs.acs.org.
S
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(9) Rodriguez, J. G.; de los Rios, C.; Lafuente, A. Tetrahedron 2005, 61
(38), 9042−9051.
AUTHOR INFORMATION
Corresponding Author
*E-mail for H.C.B.: helene.bertrand@ens.fr.
Notes
■
(10) Kvaskoff, D.; Vosswinkel, M.; Wentrup, C. J. Am. Chem. Soc.
2011, 133 (14), 5413−5424.
(11) Keith, J. M. J. Org. Chem. 2006, 71 (25), 9540−9543.
(12) Chang, S.; Lee, M.; Jung, D. Y.; Yoo, E. J.; Cho, S. H.; Han, S. K.
J. Am. Chem. Soc. 2006, 128 (38), 12366−12367.
(13) Katagiri, T.; Tsurugi, H.; Satoh, T.; Miura, M. Chem. Commun.
2008, No. 29, 3405−3407.
(14) (a) Shaikh, T. M.; Sudalai, A. Eur. J. Org. Chem. 2010, 2010 (18),
3437−3444. (b) Juricek, M.; Kouwer, P. H. J.; Rehak, J.; Sly, J.; Rowan,
A. E. J. Org. Chem. 2009, 74 (1), 21−25.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The ENS is acknowledged for a Ph.D. fellowship for S.C.. Dr. A.
Vessier
̀
es is gratefully acknowledged for cell culture facilities and
Dr. Z. Gueroui for access to the fluorescence microscope.
(15) Bijleveld, J. C.; Shahid, M.; Gilot, J.; Wlenk, M. M.; Janssen, R. A.
J. Adv. Funct. Mater. 2009, 19 (20), 3262−3270.
(16) Maisonneuve, S.; Fang, Q.; Xie, J. Tetrahedron 2008, 64 (37),
8716−8720.
REFERENCES
■
(1) (a) Demas, J. N.; DeGraff, B. A. Design and Applications of Highly
Luminescent Transition Metal Complexes. In Topics in Fluorescence
Spectroscopy; Lakowicz, J. R., Ed.; Springer: Berlin, 1994; Vol. 4 (Probe
Design and Chemical Sensing). (b) Thorp-Greenwood, F. L.
Organometallics 2012, 31 (16), 5686−5692.
(2) (a) Lo, K. K.-W.; Louie, M.-W.; Zhang, K. Y. Coord. Chem. Rev.
2010, 254 (21−22), 2603−2622. (b) Lo, K. K.-W.; Tsang, K. H.-K.;
Sze, K.-S.; Chung, C.-K.; Lee, T. K.-M.; Zhang, K. Y.; Hui, W.-K.; Li, C.-
K.; Lau, J. S.-Y.; Ng, D. C.-M.; Zhu, N. Coord. Chem. Rev. 2007, 251
(17−20), 2292−2310.
(3) (a) Baggaley, E.; Weinstein, J. A.; Williams, J. A. G. Coord. Chem.
Rev. 2012, 256 (15−16), 1762−1785. (b) Balasingham, R. G.; Coogan,
M. P.; Thorp-Greenwood, F. L. Dalton Trans. 2011, 40 (44), 11663−
11674. (c) Butler, I. S.; Kengne-Momo, R. P.; Jaouen, G.; Policar, C.;
Vessieres, A. Appl. Spectrosc. Rev. 2012, 47 (7), 531−549.
(d) Fernandez-Moreira, V.; Thorp-Greenwood, F. L.; Coogan, M. P.
Chem. Commun. 2010, 46 (2), 186−202. (e) Lo, K. K.-W.; Choi, A. W.-
T.; Law, W. H.-T. Dalton Trans. 2012, 41 (20), 6021−6047. (f) Lo, K.
K.-W.; Zhang, K. Y.; Li, S. P.-Y. Eur. J. Inorg. Chem. 2011, 2011 (24),
3551−3568. (g) Louie, M.-W.; Choi, A. W.-T.; Liu, H.-W.; Chan, B. T.-
N.; Lo, K. K.-W. Organometallics 2012, 31 (16), 5844−5855.
(h) Sacksteder, L.; Zipp, A. P.; Brown, E. A.; Streich, J.; Demas, J.
N.; DeGraff, B. A. Inorg. Chem. 1990, 29 (21), 4335−4340. (i) Thorp-
Greenwood, F. L.; Coogan, M. P.; Hallett, A. J.; Laye, R. H.; Pope, S. J.
A. J. Organomet. Chem. 2009, 694 (9−10), 1400−1406.
(4) (a) Anderson, C. B.; Elliott, A. B. S.; Lewis, J. E. M.; McAdam, C.
J.; Gordon, K. C.; Crowley, J. D. Dalton Trans. 2012, 41 (48), 14625−
14632. (b) Bartholoma, M.; Valliant, J.; Maresca, K. P.; Babich, J.;
Zubieta, J. Chem. Commun. 2009, No. 5, 493−512. (c) Wei, L.; Babich,
J. W.; Ouellette, W.; Zubieta, J. Inorg. Chem. 2006, 45 (7), 3057−3066.
(d) Wrighton, M.; Morse, D. L. J. Am. Chem. Soc. 1974, 96 (4), 998−
1003.
(5) (a) Bullock, S.; Hallett, A. J.; Harding, L. P.; Higginson, J. J.; Piela,
S. A. F.; Pope, S. J. A.; Rice, C. R. Dalton Trans. 2012, 41 (48), 14690−
14696. (b) Huang, R.; Langille, G.; Gill, R. K.; Li, C. M. J.; Mikata, Y.;
Wong, M. Q.; Yapp, D. T.; Storr, T. J. Biol. Inorg. Chem. 2013, 18 (7),
831−844. (c) Kim, T. Y.; Elliott, A. B. S.; Shaffer, K. J.; John McAdam,
C.; Gordon, K. C.; Crowley, J. D. Polyhedron 2013, 52 (0), 1391−1398.
(d) Obata, M.; Kitamura, A.; Mori, A.; Kameyama, C.; Czaplewska, J.
A.; Tanaka, R.; Kinoshita, I.; Kusumoto, T.; Hashimoto, H.; Harada,
M.; Mikata, Y.; Funabiki, T.; Yano, S. Dalton Trans. 2008, No. 25,
3292−3300. (e) Seridi, A.; Wolff, M.; Boulay, A.; Saffon, N.; Coulais,
Y.; Picard, C.; Machura, B.; Benoist, E. Inorg. Chem. Commun. 2011, 14
(1), 238−242. (f) Wolff, M.; Munoz, L.; Francois, A.; Carrayon, C.;
Seridi, A.; Saffon, N.; Picard, C.; Machura, B.; Benoist, E. Dalton Trans.
2013, 42 (19), 7019−7031.
(17) (a) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure
Solution; University of Gottingen, Gottingen, Germany, 1997. (b)
̈
̈
Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal
Structures from Diffraction Data; University of Gottingen, Gottingen,
̈
̈
Germany, 1997. (c) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837−
838.
(18) Ellanki, A. R.; Islam, A.; Rama, V. S.; Pulipati, R. P.; Rambabu, D.;
Rama Krishna, G.; Malla Reddy, C.; Mukkanti, K.; Vanaja, G. R.; Kalle,
A. M.; Shiva Kumar, K.; Pal, M. Bioorg. Med. Chem. Lett. 2012, 22 (10),
3455−3459.
(19) (a) Gu, S.; Xu, H.; Zhang, N.; Chen, W. Chem. Asian J. 2010, 5
(7), 1677−1686. (b) Stengel, I.; Mishra, A.; Pootrakulchote, N.; Moon,
S.-J.; Zakeeruddin, S. M.; Gratzel, M.; Bauerle, P. J. Mater. Chem. 2011,
21 (11), 3726−3734.
(20) (a) Choi, A. W.-T.; Louie, M.-W.; Li, S. P.-Y.; Liu, H.-W.; Chan,
B. T.-N.; Lam, T. C.-Y.; Lin, A. C.-C.; Cheng, S.-H.; Lo, K. K.-W. Inorg.
Chem. 2012, 51 (24), 13289−13302. (b) Clede, S.; Lambert, F.; Saint-
̀
Fort, R.; Plamont, M.-A.; Bertrand, H.; Vessieres, A.; Policar, C. Chem.
Eur. J., DOI: 10.1002/chem.201402471. (c) Coogan, M. P.; Fernandez-
Moreira, V.; Hess, J. B.; Pope, S. J. A.; Williams, C. New J. Chem. 2009,
33 (5), 1094−1099. (d) Reitz, G. A.; Demas, J. N.; DeGraff, B. A.;
Stephens, E. M. J. Am. Chem. Soc. 1988, 110 (15), 5051−5059.
(e) Sacksteder, L.; Lee, M.; Demas, J. N.; DeGraff, B. A. J. Am. Chem.
Soc. 1993, 115 (18), 8230−8238.
(21) (a) Garcia, L.; Lazzaretti, M.; Diguet, A.; Mussi, F.; Bisceglie, F.;
Xie, J.; Pelosi, G.; Buschini, A.; Baigl, D.; Policar, C. New J. Chem. 2013,
37 (10), 3030−3034. (b) Garcia, L.; Maisonneuve, S.; Marcu, J. O. S.;
Guillot, R.; Lambert, F.; Xie, J.; Policar, C. Inorg. Chem. 2011, 50 (22),
11353−11362.
(22) Storr, T.; Obata, M.; Fisher, C. L.; Bayly, S. R.; Green, D. E.;
Brudzinska, I.; Mikata, Y.; Patrick, B. O.; Adam, M. J.; Yano, S.; Orvig,
̃
C. Chem. Eur. J. 2005, 11 (1), 195−203.
(23) Patra, M.; Joshi, T.; Pierroz, V.; Ingram, K.; Kaiser, M.; Ferrari,
S.; Spingler, B.; Keiser, J.; Gasser, G. Chem. Eur. J. 2013, 19 (44),
14768−14772.
(24) Schulze, B.; Schubert, U. S. Chem. Soc. Rev. 2014, 43, 2522−
2571.
(25) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.;
Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.;
Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,
K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.;
Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo,
C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A.
J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma,
K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.;
Cioslowski, J.; Fox, D. J. Gaussian 09; Gaussian, Inc., Wallingford, CT,
2009.
(6) Clede, S.; Lambert, F.; Sandt, C.; Gueroui, Z.; Refregiers, M.;
Plamont, M. A.; Dumas, P.; Vessieres, A.; Policar, C. Chem. Commun.
2012, 48 (62), 7729−7731.
(7) Clede, S.; Lambert, F.; Sandt, C.; Kascakova, S.; Unger, M.; Harte,
E.; Plamont, M. A.; Saint-Fort, R.; Deniset-Besseau, A.; Gueroui, Z.;
Hirschmugl, C.; Lecomte, S.; Dazzi, A.; Vessieres, A.; Policar, C. Analyst
2013, 138 (19), 5627−5638.
(8) Chattopadhyay, B.; Vera, C. I. R.; Chuprakov, S.; Gevorgyan, V.
Org. Lett. 2010, 12 (9), 2166−2169.
T
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