Novel molecular building blocks based on the boradiazaindacene chromophore: Applications in fluorescent metallosupramolecular coordination polymers

Article abstract of DOI:10.1002/chem.200802538

We designed and synthesized novel boradiazaindacene (Bodipy) derivatives that are appropriately functionalized for metal-ion-mediated supramolecular polymerization. Thus, ligands for 2-terpyridyl-, 2,6-terpyridyl-, and bipyridyl-functionalized Bodipy dyes

Full text of DOI:10.1002/chem.200802538

DOI: 10.1002/chem.200802538
Novel Molecular Building Blocks Based on the Boradiazaindacene
Chromophore: Applications in Fluorescent Metallosupramolecular
Coordination Polymers
ꢀ. Altan Bozdemir,[a] Onur Bꢁyꢁkcakir,[a, b] and Engin U. Akkaya*[a]
Abstract: We designed and synthesized
novel boradiazaindacene (Bodipy) de-
rivatives that are appropriately func-
manner. Octahedral coordinating metal
ions such as ZnII result in polymeri-
zation at a stoichiometry corresponding
to two terpyridyl ligands to one ZnII
ion. However, at increased metal ion
concentrations, the dynamic equilibria
are re-established in such a way that
the monomeric metal complex domi-
nates. The position of equilibria can
easily be monitored by 1H NMR and
fluorescence spectroscopies. As expect-
ed, although open-shell FeII ions form
similar complex structures, these cat-
ions quench the fluorescence emission
of all four functionalized Bodipy li-
gands.
tionalized
for
metal-ion-mediated
supramolecular polymerization. Thus,
ligands for 2-terpyridyl-, 2,6-terpyridyl-,
and bipyridyl-functionalized Bodipy
dyes were synthesized through Sonoga-
shira couplings. These fluorescent
building blocks are responsive to metal
Keywords: coordination polymers ·
dyes/pigments
self-assembly
coupling
·
polymerization
·
·
Sonogashira
ions in
a
stoichiometry-dependent
Introduction
tion polymers were obtained by utilizing terpyridyl–ZnII co-
ordination.
Boradiazaindacene
[18–19]
Coordination polymers represent a distinct group of supra-
molecular polymers,[1–6] which have attracted great attention
in recent years.[7–12] The degree of polymerization in such
polymers is primarily controlled by the concentration of the
building blocks in solution and the strength of interaction
between the ligand and the metal ion. The dynamic nature
of the equilibria governing the extent of polymerization pro-
vides enormous potential in manipulating the macroscopic
properties of these polymers, whether in solution or in other
phases. Recent studies in the groups of Wꢀrthner[13–15] and
Schubert[16,17] established the viability of the terpyridyl–
metal coordinative bond as a promising strategy for the
preparation of such self-assembled supramolecular poly-
mers. In these studies, fluorescent supramolecular coordina-
dyes (also known as bodipy dyes,
boron-dipyrrin dyes, and BDPs) are bright fluorophores
with many desirable properties, including very versatile
chemistry of the parent fluorophore.[20–23] In recent years,
there has been a flurry of activity investigating many deriva-
tives and numerous applications of these dyes. Among
these, fluorescent chemosensors,[24–27] molecular logic
gates,[28] fluorescent organogels,[29] sensitizers in dye-sensi-
tized solar cells,[30,31] cellular imaging,[32] and applications in
photodynamic therapy[33,34] are particularly noteworthy.
There have also been previous reports of bipyridyl[35,36] and
terpyridyl[37–39] derivatives of bodipy dyes and their ZnII
complexes, although the monomeric derivatives were not
designed for self-assembled polymerization. Herein, we
report 2- and 2,6-derivatized bodipy dyes with one or two li-
gands per bodipy unit, placed on opposite ends of the fluo-
rophore core. In the case of the bis(terpyridyl) derivative,
clear signals of polymerization are observed by using
1H NMR spectroscopy upon gradual addition of ZnII. The
additional data obtained from the monoterpyridyl derivative
also corroborates the interpretation of the spectral changes
observed by using NMR spectroscopy. In addition, the
ligand is attached to the bodipy core through triple bonds,
and any changes in charge density distribution are transmit-
ted to the core. The result is a significant enhancement in
[a] Dr. ꢁ. A. Bozdemir, O. Bꢀyꢀkcakir, Prof. Dr. E. U. Akkaya
Department of Chemistry and UNAM-Institute of Materials Science
and Nanotechnology
Bilkent University, 06800 Ankara (Turkey)
Fax : (+90)312-266-4068
E-mail: eua@fen.bilkent.edu.tr
[b] O. Bꢀyꢀkcakir
Department of Chemisty, Middle East Technical University
06531 Ankara (Turkey)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200802538.
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Chem. Eur. J. 2009, 15, 3830 – 3838

FULL PAPER
the emission intensity upon ZnII binding, which is accompa-
nied by a small blueshift in the absorption spectrum. Thus,
formation of the coordination polymers were also evidenced
by fluorescence changes of the fluorophores. To the best of
our knowledge, signaling of metal-ion-mediated polymeri-
zation through a clear and observable change in the emis-
sion intensity was unprecedented.
particularly relevant in ion-sensing applications based on
earlier literature data in which chromophores were tethered
by bipyridyl linkages.[39]
NMR spectroscopic study of the complexation and coordi-
nation polymer formation: Metal ion complexation results
in characteristic signal changes in the 1H NMR spectra
(Figure 1). First, the monoterpyridyl-bodipy compound 5 is
Results and Discussion
Synthesis of the building blocks: To improve solubility in or-
ganic solvents, our synthetic approach required the initial
synthesis of a bodipy derivative with 3,5-bis
groups at the meso positions. We started our synthesis with
3,5-bis(decyloxy)benzaldehyde 1, which can be obtained by
ACHTUNGTREN(NUGN decyloxy)phenyl
ACHTUNGTRENNUNG
a two-step conversion from commercially available 3,5-dihy-
droxybenzyl alcohol. Standard procedures yielded bright
green emitting bodipy dye 2 in 30% yield. Addition of dif-
ferent molar ratios of I2/HIO3 to bodipy 2 resulted in either
monoiodinated 3, or diiodinated 4 bodipy derivatives.[40] Li-
gands were tethered to the fluorophore unit through Sono-
gashira couplings using either 4-ethynylphenylterpyridyl or
bis(ethynylbipyridyl), both of which were described by Zies-
sel and co-workers.[39,41] The reactions proceeded smoothly,
yielding target compounds 5, 6, 7, and 8. Maximal absorp-
tion peaks showed larger redshifts in the cases of 2,6-bis-
substituted products (571 and 577 nm, 8 and 7 respectively).
Compound 6 was designed as the monomeric building block
for a fluorescent supramolecular coordination polymer.
Compound 5 is a reference compound, expected to assist us
in identifying spectral changes on polymer formation. Bipyr-
idyl derivatives 7 and 8 are different types of building block
that might be useful in the construction of gridlike struc-
tures and metal-ion-coordination-mediated energy transfer
and light-harvesting systems. Compound 8 (Scheme 1) is
Figure 1. 1H NMR spectra obtained by the titration of 5 in 60:40 CDCl3/
[D6]DMSO (13 mm) with ZnACHTNUTGRNEUNG
(OTf)2. ZnII/5 ratio varies from bottom to
top as 0:1, 0.25:1, 0.5:1, 0.75:1, 1:1, 1:1.5.
highly instructive. As expected, whereas the 1H NMR signals
corresponding to the bodipy core are not noticeably shifted
upon complexation, terpyridyl signals shift to low field on
ZnII complex formation. Addition of 0.25 equivalents of ZnII
to 5 results in some signal broadening together with a down-
field shift. When the amount of ZnII is increased to
0.5 equivalents, the molar ratio is just right for the 2:1 (52–
ZnII) complex. The most downfield sharp signal has been
identified as the H3’ singlet. In the 2:1 complex, it appears
at d=9.3 ppm. The most characteristic change is that of the
H6 (and H6’) signal: complex formation induces a signifi-
cant upfield shift because those hydrogen nuclei will be
brought into the shielding zone of the pyridine rings of the
other terpyridyl. As a result, in the metal-free ligand 5, the
H6 nuclei resonate at d=8.7 ppm, but in the 2:1 complex,
this signal moves to d=7.7 ppm. As previously demonstrat-
ed, further addition of ZnII decreases the equilibrium con-
centration of the dimeric 2:1 complex in favor of the “open
form” (Scheme 2). As a result, the sharp downfield H3’ sin-
glet decreases in intensity as more and more ZnII is added.
At 1:1.5 equivalents of ZnII, the signal at d=9.3 ppm practi-
˘
Abstract in Turkish: Bu Åalıs¸mada, metal iyonları aracılıgıyla
supramolekꢀler polimerizasyon iÅin uygun s¸ekilde fonksiyon-
landırılmıs¸ yeni boradiazaindasen (Bodipy) tꢀrevleri tasar-
lanmıs¸ ve sentezlenmis¸tir. Bu amaÅla, ligand olarak Sonogas-
hira reaksiyonu ile 2- ve 2,6-terpiridil ve bipiridil gruplarını
iÅeren Bodipy boyarmaddeleri sentezlenmis¸tir. Bu floresan
˘
yapı blokları stokiyometriye baglı bir biÅimde metal iyonları-
na duyarlılık gçsterirler. ZnII gibi oktahedral koordinasyon
II
˘
egilimi olan metal iyonları, iki terpiridil ligandına bir Zn
iyonu tekabꢀl edecek bir stokiyometride polimerizasyona yol
aÅmaktadırlar. Bununla beraber, yꢀksek metal iyonu deris¸im-
˘
lerinde monomerik metal kompleksinin baskın olacagı bir bi-
Åimde, dinamik dengeler yeniden kurulmaktadır. Bu dengele-
1
rin pozisyonu H NMR ve fluoresans spektroskopileriyle ko-
˘
laylıkla izlenebilmektedir. Beklenildigi gibi, benzer kompleks
II
˘
yapılar olus¸turmasına ragmen Fe iyonu, sentezlenen tꢀm
fonksiyonalize Bodipy ligandlarının emisyonlarını sçnꢀmlen-
dirmektedir.
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3831

E. U. Akkaya et al.
Scheme 1. a) i) 1, 2,4-dimethyl pyrrole, trifluoroacetic acid (TFA), CH2Cl2, RT, 1 d, ii) 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), NEt3,
BF3·OEt2, CH2Cl2, RT, 2 h; b) 2, I2 (1 equiv), HIO3, EtOH/H2O, 60 8C, 1 h; c) 2, I2 (2 equiv), HIO3, EtOH/H2O, 60 8C, 1 h; d) 3, 4’-ethynyl-2,2’,6’2’’-terpyr-
idine, [PdCl
amine, 508C, 40 min then RT, 1 d; f) 4, 4’-ethynyl-2,2’,6’2’’-terpyridine, [PdCl
yl-2,2’-bipyridine, [PdCl2A(PPh3)2], CuI, THF/diisopropylamine, 508C, 40 min then RT, 1 d. R=decyl.
G
2ACHTUGNRTEN(NUNG PPh3)2], CuI, THF/diisopropyl-
cally disappears and a new sin-
glet at d=9.1 ppm becomes
prominent. That particular
signal corresponds to the open
1:1 ZnII complex, 5–ZnII. In
this complex, other coordina-
tion sites of ZnII should be oc-
cupied with DMSO molecules
or triflate ions. Bis(terpyridyl)
compound 7 displays very clear
signs of polymerization on ad-
dition of ZnII (Figure 2). Upon
addition of 0.25 equivalents of
ZnII, the 1H NMR signals
become very broad. The addi-
tion of one equivalent of ZnII
should generate the largest po-
lymer chain lengths, and this is
Scheme 2. Formation of dimeric and open-form structures by the addition of ZnACHTNUTGRNEUNG(OTf)2.
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Fluorescent Coordination Polymers
FULL PAPER
vestigation of the complexation and coordination polymer
formation: To synthesize the building blocks, terpyridyl-
phenyl and bipyridyl groups have been attached to the fluo-
rophore core through ethynyl spacers; there is some conju-
gation and thus electronic communication between the
ligand moieties and the bodipy cores. As a result, we ob-
serve spectral changes not only in peaks that correspond to
p–p* transitions in the oligopyridine moieties, but in bodipy
S0–S1 transitions as well. For example, in the reference com-
pound 5, the increase in the absorption of the peak at
325 nm peak and the shoulder at 400 nm are due to terpyr-
idyl ligand–ZnII coordinative interactions. As the inset in
Figure 3 clearly shows, above 0.5 equivalents of ZnII, the
change in the absorption levels off very quickly, indicating a
strong affinity between the ligand and the ZnII in this partic-
ular solvent system (80:20 CHCl3/MeOH). In addition, there
is a small increase of the bodipy absorption peak at 536 nm
as the added amount of ZnII is increased (the extinction co-
efficient (e) changes from 95000 to 104000 cmÀ1 mÀ1). ZnII ti-
tration of the monotopic ligand 5 shows a gradual increase
in the emission intensity (Figure 4) and at saturation the in-
tensity of the bodipy emission is nearly doubled. There is a
concomitant small blueshift in the emission intensity in this
peak, from 572 to 563 nm. The equilibrium constant (K1) for
the first binding event (5–ZnII), determined by following the
absorbance changes at 325 nm, is 6.8ꢃ106 mÀ1. ZnII titration
of the ditopic bis(terpyridyl) bodipy ligand 7 shows similar
changes. There are increases in the absorption peaks at 325,
400 (shoulder), and 577 nm (bodipy S0–S1transition)
(Figure 5). As expected, the absorption changes at 325 nm
(Figure 5, inset) level off only after one equivalent of ZnII
ions were added (1:1). In the fluorescence spectrum
(Figure 6), there is a minor increase (+30%) in the intensity
with just a few nanometers of blueshift in the peak position
(from 608 to 602 nm). As expected, the bipyridyl–ZnII inter-
action is weaker, and coordination stoichiometry and spatial
arrangement of the bodipy chromophores should be differ-
Figure 2. 1H NMR spectra obtained by the titration of 7 in 60:40 CDCl3/
[D6]DMSO (13 mm) with ZnACHTNUTGRNEUNG
(OTf)2. ZnII/7 ratio varies from bottom to
top as 0:1, 0.25:1, 0.5:1, 0.75:1, 1:1, 2:1, 3:1.
clearly reflected in the broad-
ness of the signals. As expect-
ed, the pyridine ring protons of
the terpyridyl group shifted
downfield. Most interestingly,
addition
of
more
than
0.5 equivalents of ZnII to
ligand 7 results in sharpening
1
of the H NMR signals of the
aromatic protons. Upon addi-
tion of one or more equiva-
lents of ZnII, the NMR spectra
display a clear predominance
of the 1:1 open-form complex,
with very distinctively sharper
monomeric aromatic hydrogen
signals (Scheme 3).
Absorbance and steady-state
fluorescence spectroscopic in-
Scheme 3. Formation of polymeric and open-form structures by the addition of ZnACHTNUTGRNEUNG(OTf)2.
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3833

E. U. Akkaya et al.
Figure 3. UV/Vis spectra obtained by the titration of 5 in 80:20 CHCl3/
MeOH (5.0ꢃ10À6 m) with Zn
ACTHUNTRGNE(UGN OTf)2. The inset shows the absorption coef-
ficient at 325 nm as a function of the ZnII/5 ratio.
Figure 5. UV/Vis spectra obtained by the titration of 7 in 80:20 CHCl3/
MeOH (5.0ꢃ10À6 m) with Zn
ACTHUNTRGNE(UGN OTf)2. The inset shows the absorption coef-
ficient at 325 nm as a function of ZnII/7 ratio.
Figure 4. Fluorescence spectra obtained by the titration of 5 in 80:20
CHCl3/MeOH (5.0ꢃ10À6 m) with Zn
ACTHNUTRGNEN(UG OTf)2.
ent from the terpyridine derivatives. On saturation with
ZnII, the absorption spectra of compound 6 (Figure 7) dis-
play minor changes at 380 (decrease) and 541 nm (increase),
the emission peak intensity increases (+44%, Figure 8), and
the peak shifts blue (from 567 to 558 nm). The K1 value for
the first binding event (6–ZnII), determined by following the
emission changes at the peak wavelength (558 nm), is 2.2ꢃ
105 mÀ1. In contrast, bis(bipyridylbodipy) 8 shows a some-
what complicated response in absorption spectra during ti-
tration (Figure 9). Whereas the peak at 400 nm behaves nor-
mally (an increase with an expected saturation behavior),
the bodipy peak shows an increase: growth of a shoulder at
530 nm and then disappearance of the shoulder with a final
increase at 562 nm. We speculate that the growth of a
shoulder is suggestive of interchromophoric stacking with
Figure 6. Fluorescence spectra obtained by the titration of 7 in 80:20
CHCl3/MeOH (5.0ꢃ10À6 m) with Zn
ACTHNUTRGNEN(UG OTf)2.
lower ZnII to ligand ratios, in which two bodipys might be
brought together in an octahedral arrangement. Increasing
ZnII concentration would of course favor an open form re-
sembling that of the terpyridyl derivatives. The K1 value for
the first binding event (8–ZnII), determined by following the
emission changes at the peak wavelength (588 nm), is 1.7ꢃ
106 mÀ1. Emission spectra (Figure 10) are supportive of this
speculation; at lower ZnII concentrations, binding causes
more spectral blueshift rather than intensity change, but at
larger proportions of ZnII, bodipy groups are removed from
each other with the formation of open-form structures, de-
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Fluorescent Coordination Polymers
FULL PAPER
Figure 7. UV/Vis spectra obtained by the titration of 6 in 80:20 CHCl3/
Figure 9. UV/Vis spectra obtained by the titration of 8 in 80:20 CHCl3/
MeOH (5.0ꢃ10À6 m) with Zn
ACTHNUTRGNEN(UG OTf)2.
MeOH (5.0ꢃ10À6 m) with Zn
ACTHNUTRGNEN(UG OTf)2.
Figure 10. Fluorescence spectra obtained by the titration of 8 in 80:20
CHCl3/MeOH (5.0ꢃ10À6 m) with Zn
(OTf)2.
Figure 8. Fluorescence spectra obtained by the titration of 6 in 80:20
CHCl3/MeOH (5.0ꢃ10À6 m) with Zn
(OTf)2.
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
Table 1. Spectroscopic[a] data for free and ZnII-complexed ligands.
creasing the effects of self-quenching of the bodipy fluoro-
phores. The complex formation with FeII quenches the fluo-
rescence emission in all cases (see the Supporting Informa-
tion), which is not surprising considering that FeII is an
open-shell cation with available oxidation states. Spectro-
scopic data for the free ligands and their ZnII complexes are
presented in Table 1.
[b]
[b]
labs
labs
lf
lf[b]
emax
[mÀ1 cmÀ1
emax
[mÀ1 cmÀ1
]
ff
ff[b]
[nm] [nm] [nm] [nm]
G
]
U
5
6
7
8
536
541
577
571
535
543
576
567
572
567
608
598
563
558
602
588
95000
67000
83200
86000
104000
81000
98000
136000
0.27[c] 0.29[c]
0.29[c] 0.32[c]
0.47[d] 0.49[d]
0.53[d] 0.67[d]
[a] Determined in 80:20 CHCl3/MeOH solution. [b] Recorded in the
presence of ZnII. [c] Rhodamine 6G in water (ff =0.95) was used as refer-
ence. [d] Sulforhodamine 101 hydrate in ethanol (ff =0.90) was used as
reference.
Mass spectrometric studies of the metal complexes: Mass
spectrometry of the polymeric species does not yield large
molecular weight peaks, in accordance with previous reports
on metallosupramolecular polymers.[10] However, at any
ratio near 1:2 equivalency between the ZnII ions and 5, four
easily identifiable peaks are observed by using MALDI-
Both the open form with the triflate counterions, and the di-
meric complex shown in Scheme 2 appear on the mass spec-
trum (see the Supporting Information).
TOF spectrometry: 52–Zn at 1999.4 amu, 5–Zn
ACHTUNGRTEN(NUNG OTf)2 at
1918.8 amu, 5–Zn(OTf)2 at 1183.7 amu, and 5 at 968.7 amu.
ACHTUNGTRENNUNG
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E. U. Akkaya et al.
500 mL round-bottomed flask containing CH2Cl2 (250 mL), and the reac-
tion mixture was stirred for 3 h at room temperature. The reaction mix-
ture was then washed with water and the organic phase was evaporated
at reduced pressure. Silica gel column chromatography using CHCl3 as
the eluant gave 1 as a waxy solid (8.1 g, 90%). 1H NMR (400 MHz,
CDCl3): d=9.80 (1H, s; CHO), 6.93 (2H, s; ArH), 6.60 (1H, s; ArH),
3.92 (4H, t, J=6.49 Hz; OCH2), 1.75–1.65 (4H, m; CH2), 1.41–1.32 (4H,
m; CH2), 1.20 (24H, s; CH2), 0.80 ppm (6H, t, J=6.59 Hz; CH3);
13C NMR (100 MHz, CDCl3): d=192.0, 160.8, 138.4, 108.1, 107.1, 68.5,
31.9, 29.6, 29.5, 29.3, 29.1, 26.0, 22.7, 14.1 ppm.
Conclusion
Through the use of Sonogashira couplings, four functional
building blocks carrying bodipy fluorophores were synthe-
sized. Ter- and bipyridyl ligands have been repeatedly
shown to be very useful in the construction of supramolec-
ular structures. Terpyridyl is a strong enough ligand for ZnII
ions, and the addition of zinc triflate forms a fluorescent co-
ordination polymer. This polymerization process can be
easily followed by the observation of fluorescence character-
istics. Ditopic bis(terpyridyl) bodipy ligand 7 shows clear
evidence of polymerization when 0.5 equivalents of ZnII ions
were added. The addition of ZnII changes the dynamic equi-
4,4-Difluoro-8-[3’,5’-bisACTHNUGRTNEUNG(decyloxy)phenyl]-1,3,5,7-tetramethyl-4-bora-
3a,4a-diaza-s-indacene (2): 2,4-Dimethyl pyrrole (15.8 mmol, 1.50 g) and
1 (7.17 mmol, 3 g) were added to a 1 L round-bottomed flask containing
argon-degassed CH2Cl2 (400 mL). One drop of TFA was added and the
solution was stirred under nitrogen at room temperature for 1 d. After
addition of a solution of DDQ (7.17 mmol, 1.628 g) in CH2Cl2 (100 mL),
stirring was continued for 30 min. Et3N (6 mL) and BF3·OEt2 (3 mL)
were successively added and after 30 min, the reaction mixture was
washed three times with water and dried over anhydrous Na2SO4. The
solvent was evaporated and the residue was purified by silica gel column
chromatography using 2:1 CHCl3/hexane as the eluant to give 2 as a red
waxy solid (1.381 g, 30%). 1H NMR (400 MHz, CDCl3): d=6.45 (1H, s;
ArH), 6.35 (2H, s; ArH), 5.90 (2H, s; H2, H6), 3.85 (4H, t, J=6.56 Hz;
OCH2), 2.47 (6H, s; CH3), 1.72–1.62 (4H, m; CH2), 1.49 (6H, s; CH3),
1.40–1.30 (4H, m; CH2), 1.20 (24H, s; CH2), 0.80 ppm (6H, t, J=
6.53 Hz; CH3); 13C NMR (100 MHz, CDCl3): d=161.2, 155.4, 143.2,
136.4, 131.2, 121.0, 106.4, 102.3, 68.4, 31.9, 29.6, 29.5, 29.3, 29.2, 26.0, 22.7,
14.6, 14.2, 14.0 ppm; HRMS (TOF-ESI): m/z calcd for C39H59BF2N2O2Na:
658.4572 [M+Na]+; found: 658.4542 [M+Na]+.
1
librium concentration of the polymer, and the H NMR sig-
nals become more sharp as more ZnII ions are added, which
indicates a monomeric complex (open form). With their
lower affinities, bipyridyl derivatives can also be useful as
fluorescent chemosensors when considering that intracellu-
lar ZnII concentrations can vary by six orders of magnitude.
A fluorescent coordination polymer may find utility in elec-
trochromic devices or in other device applications in which
reversible changes between states of different physical prop-
erties is an asset.
4,4-Difluoro-8-[3’,5’-bisACTHNUTRGNEUG(N decyloxy)phenyl]-2-iodo-1,3,5,7-tetramethyl-4-
bora-3a,4a-diaza-s-indacene (3): Compound 2 (1.91 mmol, 1.21 g) and
iodine (1.52 mmol, 0.387 g) were added to a 500 mL round-bottomed
flask and to this solution iodic acid (1.52 mmol, 0.268 g) dissolved in
water (2 mL) was added. The reaction mixture was stirred at 608C and
was monitored by TLC (1:1 CHCl3/hexanes). When TLC indicated that
all the starting material had been consumed, the reaction was quenched
by the addition of a saturated aqueous solution of Na2S2O3 (100 mL) and
the product was extracted into CHCl3. The solvent was evaporated and
the residue was purified by silica gel column chromatography using 1:1
CHCl3/hexane as the eluant to give 3 as a red waxy solid (0.98 g, 67%).
1H NMR (400 MHz, CDCl3): d=6.48 (1H, s; ArH), 6.32 (2H, d, J=
1.90 Hz; ArH), 5.97 (1H, s; H2), 3.85 (4H, t, J=6.60 Hz; OCH2), 2.55
(3H, s; CH3), 2.49 (3H, s; CH3), 1.72–1.62 (4H, m; CH2), 1.49 (6H, s;
CH3), 1.40–1.30 (4H, m; CH2), 1.20 (24H, s; CH2), 0.8 ppm (6H, t, J=
6.60; CH3); 13C NMR (100 MHz, CDCl3): d=161.3, 157.7, 154.4, 145.1,
143.2, 141.5, 136.2, 131.6, 130.7, 122.1, 106.2, 102.5, 84.1, 68.4, 38.2, 33.8,
32.9, 31.9, 31.3, 29.7, 29.6, 29.5, 29.4, 29.3, 29.2, 28.8, 28.2, 26.1, 26.0, 25.8,
22.7, 16.5, 15.7, 14.7, 14.5, 14.1 ppm; HRMS (TOF-ESI): m/z calcd for
C39H58BF2IN2O2Na: 784.3538 [M+Na]+; found: 784.3513 [M+Na]+.
Experimental Section
General: 1H and 13C NMR spectra were recorded on a Bruker DPX-400
spectrometer (operating at 400 MHz for 1H NMR and 100 MHz for
13C NMR) in CDCl3 and [D6]DMSO with tetramethylsilane as an internal
standard. All spectra were recorded at 258C and coupling constants (J
values) are given in Hz. Chemical shifts are given in parts per million
(ppm). Absorption spectra were obtained by using a Varian Cary-100
spectrophotometer. Fluorescence measurements were conducted on a
Varian Eclipse spectrofluorimeter. Mass spectra were recorded at the
Ohio State University Mass Spectrometry and Proteomics Facility, Ohio,
USA. Reactions were monitored by TLC using Merck TLC Silica gel 60
F254 and Merck Aluminium Oxide 60 F254. Silica gel column chromatogra-
phy was performed over Merck Silica gel 60 (particle size: 0.040–
0.063 mm, 230–400 mesh ASTM). Aluminium oxide column chromatog-
raphy was performed using Merck Aluminium Oxide 90 active neutral.
4’-(4-Ethynylphenyl)-2,2’,6’,2’’-terpyridine, 5,5’-diethynyl-2,2’-bipyridine,
and 5-ethynyl-2,2’-bipyridine were synthesized according to literature
procedures.[42,43] Anhydrous tetrahydrofuran was obtained by heating at
reflux over sodium/benzophenone prior to use. All other reagents and
solvents were purchased from Aldrich and used without further purifica-
tion.
4,4-Difluoro-8-[3,5-bisACTHNUTRGNE(NUG decyloxy)phenyl]-2,6-diiodo-1,3,5,7-tetramethyl-4-
bora-3a,4a-diaza-s-indacene (4): Compound 2 (2.47 mmol, 1.57 g) and
iodine (6.18 mmol, 1.57 g) were added to a 500 mL round-bottomed
flask. A solution of iodic acid (4.93 mmol, 0.87 g) in water (2 mL) was
added and the reaction mixture was stirred at 608C and monitored by
TLC (1:1 CHCl3/hexane). When all the starting material had been con-
sumed, the reaction was quenched by the addition of a saturated aqueous
solution of Na2S2O3 (100 mL) and the product was extracted into CHCl3.
The solvent was evaporated and the residue was purified by silica gel
column chromatography using 1:1 CHCl3/hexane as the eluant to give 4
as a red waxy solid (2.09 g, 95%). 1H NMR (400 MHz, CDCl3): d=6.49
(1H, s; ArH), 6.28 (2H, s; ArH), 3.85 (4H, t, J=6.45 Hz; OCH2), 2.55
(6H, s; CH3), 1.73–1.63 (4H, m; CH2), 1.49 (6H, s; CH3), 1.40–1.30 (4H,
m; CH2), 1.20 (24H, s; CH2), 0.80 ppm (6H, t, J=6.32 Hz; CH3);
13C NMR (100 MHz, CDCl3): d=161.4, 156.7, 145.4, 141.4, 136.1, 131.0,
106.1, 102.7, 85.5, 68.5, 31.9, 29.6, 29.5, 29.4, 29.3, 29.1, 26.0, 22.7, 16.9,
16.0, 14.1 ppm; HRMS (TOF-ESI): m/z calcd for C39H57BF2I2N2O2Na:
910.2505 [M+Na]+; found: 910.2495 [M+Na]+.
UV/Vis and fluorescence titration experiments: UV/Vis and fluorescence
titrations were conducted at 258C as constant host titrations. Aliquots of
ZnACHTUNGTRENNUNG(OTf)2 (0.025 mm in 80:20 CHCl3/MeOH) and solvent mixture (80:20
CHCl3/MeOH) were added to a solution of 5, 6, 7, or 8 (0.025 mm in
80:20 CHCl3/MeOH) to obtain the desired metal to ligand ratio. After
each addition, UV/Vis absorption and fluorescence spectra were record-
ed. (lex =535 nm for 5 and 6, and 570 nm for 7 and 8).
1H NMR titration experiments: Aliquots of Zn
ACTHNUTRGNE(UNG OTf)2 (13 mm and 10 mm
in 60:40 CDCl3/[D6]DMSO), respectively) and solvent mixture (60:40
CDCl3/[D6]DMSO) were added to a solution of 5 (13 mm in 60:40
CDCl3/[D6]DMSO) or 7 (10 mm in 60:40 CDCl3/[D6]DMSO) to obtain
the desired metal-to-ligand ratio, and after each addition, 1H NMR spec-
tra were recorded at 258C.
3,5-Bis
ACHTUNGTRENNUNG(decyloxy)benzaldehyde (1): 3,5-BisACHTUGNTREN(NUGN decyloxy)benzyl alcohol
(21.40 mmol, 9.00 g) and PCC (53.49 mmol, 11.53 g) were added to a
3836
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Chem. Eur. J. 2009, 15, 3830 – 3838

Fluorescent Coordination Polymers
FULL PAPER
4,4-Difluoro-8-[3’,5’-bis
4’’-yl)ethynylphenyl]-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene
(5): Compound (0.30 mmol, 0.23 g), 4’-ethynyl-2,2’;6’2’’-terpyridine
(0.60 mmol, 0.20 g), [PdCl2A(PPh3)2] (0.018 mmol, 12.64 mg), CuI
G
CDCl3): d=161.3, 158.0, 156.2, 153.9, 151.2, 145.5, 142.2, 138.7, 136.0,
132.6, 129.9, 122.2, 120.5, 114.1, 106.2, 102.5, 93.1, 87.1, 68.5, 31.9, 29.7,
29.5, 29.3, 29.2, 29.1, 26.0, 22.7, 14.8, 13.5 ppm; HRMS (MALDI-TOF):
m/z calcd for C92H122B2F4N6O4: 1472.965 [M]+; found: 1473.120 [M]+.
3
(0.03 mmol, 5.71 mg), and freshly distilled THF (10 mL) were added to a
50 mL Schlenk tube. Diisopropylamine (5 mL) was added and the result-
ing suspension was extensively deaerated by bubbling with argon at 508C
for 40 min. The reaction mixture was stirred at room temperature for 1 d.
The solvent was removed under reduced pressure and the residue was
washed with water (100 mL) and extracted into CHCl3. The organic layer
was evaporated and column chromatographic separation of the residue
on neutral alumina using 1:1 CHCl3/hexane as the eluant gave 5 as a
purple solid. (0.203 g, 70%). 1H NMR (400 MHz, CDCl3): d=8.67 (2H,
s; H3’’’, H5’’’), 8.65 (2H, d, J=5.78 Hz; H6’’, H6’’’’), 8.58 (2H, d, J=
7.94 Hz; H3’’, H3’’’’), 7.82–7.75 (4H, m; H4’’, H4’’’’, ArH), 7.51 (2H, d,
J=8.23 Hz; ArH), 7.30–7.25 (2H, m; H5’’, H5’’’’), 6.48 (1H, s; H4’), 6.37
(2H, d, J=1.93 Hz; H2’, H6’), 5.97 (1H, s; H6), 3.87 (4H, t, J=6.57 Hz;
OCH2), 2.66 (3H, s; CH3), 2.52 (3H, s; CH3), 1.73–1.63 (4H, m; CH2),
1.65 (3H, s; CH3), 1.52 (3H, s; CH3), 1.40–1.30 (4H, m; CH2), 1.20 (24H,
s; CH2), 0.80 ppm (6H, t, J=6.63 Hz; CH3); 13C NMR (100 MHz,
CDCl3): d=161.3, 156.1, 156.0, 149.4, 149.1, 137.7, 137.0, 136.1, 131.7,
127.2, 124.5, 123.9, 121.4, 118.6, 106.2, 102.4, 95.6, 83.8, 68.5, 31.9, 29.6,
29.5, 29.4, 29.3, 29.2, 26.0, 22.7, 14.8, 14.1 ppm; HRMS (TOF-ESI): m/z
calcd for C62H72BF2N5O2Na: 989.5661 [M+Na]+; found: 989.5676
[M+Na]+.
4,4-Difluoro-8-[3’,5’-bisACTHNUTRGNE(NUG decyloxy)phenyl]-2,6-bis(2’’,2’’’-bipyridine-5’’-eth-
ynyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (8): Compound 4
(0.161 mmol, 143 mg), 5-ethynyl-2,2’-bipyridine (0.972 mmol, 175 mg),
[PdCl2ACTHNUGTRNE(UGN PPh3)2] (0.096 mmol, 6.74 mg), CuI (0.016 mmol, 3 mg), and fresh-
ly distilled THF (10 mL) were added to a 50 mL Schlenk tube. Diisopro-
pylamine (5 mL) was added and resulting suspension was extensively
deaerated by bubbling with argon at 508C for 40 min. After degassing,
the reaction mixture was stirred at 408C for 1 d. After removal of the sol-
vents under reduced pressure, the residue was washed with water
(100 mL) and extracted into CHCl3. The solvent was removed and sepa-
ration by column chromatography on silica gel using 1% methanol/
CHCl3 as the eluant gave 8 as a blue solid. (0.128 g, 80%). 1H NMR
(400 MHz, CDCl3): d=8.68 (2H, s; H6’’), 8.61 (2H, d, J=4.52 Hz; H6’’’),
8.40–8.30 (4H, m; H3’’, H3’’’), 7.80–7.75 (4H, m; H4’’, H4’’’), 7.30–7.20
(2H, m; H5’’, H5’’’), 6.51 (1H, s; H4’), 6.38 (2H, d, J=1.63 Hz; H2’,
H6’), 3.88 (4H, t, J=6.54 Hz; OCH2), 2.68 (6H, s; CH3), 1.74–1.64 (4H,
m; CH2), 1.67 (6H, s; CH3), 1.41–1.31 (4H, m; CH2), 1.20 (24H, brs;
CH2), 0.79 ppm (6H, t, J=6.19 Hz; CH3); 13C NMR (100 MHz, CDCl3):
d=161.4, 159.2, 155.9, 153.0, 151.3, 149.3, 145.3, 143.1, 140.6, 138.9, 135.9,
131.5, 124.2, 121.4, 120.4, 116.2, 106.0, 102.7, 93.5, 86.0, 68.5, 31.9, 29.5,
29.4, 29.3, 29.1, 26.0, 22.7, 14.1, 13.8, 13.4 ppm; HRMS (MALDI-TOF):
m/z calcd for C63H71BF2N6O2: 992.570 [M]+; found: 992.741 [M]+.
4,4-Difluoro-8-[3’,5’-bisACHTUNGTRENNUNG(decyloxy)phenyl]-2,6-bis[p-(2’’,2’’’,6’’’,2’’’’-terpyri-
din-4’’-yl)ethynylphenyl]-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-inda-
cene (7): Compound 4 (0.338 mmol, 0.30 g), 4’-ethynyl-2,2’;6’2’’-terpyri-
dine (1.182 mmol, 0.394 g), [PdCl2ACHTNUGTRNEUNG(PPh3)2] (0.0203 mmol, 14.23 mg), CuI
(0.034 mmol, 6.44 mg), and freshly distilled THF (10 mL) were added to
a 50 mL Schlenk tube. Diisopropylamine (5 mL) was added and the re-
sulting suspension was extensively deaerated by bubbling with argon at
508C for 40 min. After degassing, the reaction mixture was stirred at
room temperature for 1 d. Solvents were removed under reduced pres-
sure and the residue was washed with water (100 mL) and extracted into
CHCl3. The organic layer was evaporated and separation by column
chromatography on neutral alumina using 1:1 CHCl3/hexane as the
Acknowledgements
The authors gratefully acknowledge support from Scientific and Techno-
logical Research Council of Turkey (TUBITAK), grant number TBAG-
108T212, and Turkish Academy of Sciences (TUBA).
eluant gave
7
as a blue solid. (0.382 g, 87%). 1H NMR (400 MHz,
CDCl3): d=8.68 (4H, s; H3’’’, H5’’’), 8.64 (4H, d, J=6.55 Hz; H6’’,
H6’’’’), 8.61 (4H, d, J=7.94 Hz; H3’’, H3’’’’), 7.86–7.79 (4H, m; H4’’,
H4’’’’), 7.82 (4H, d, J=8.03 Hz; ArH), 7.52 (4H, d, J=8.15 Hz; ArH),
7.33–7.27 (4H, m; H5’’, H5’’’’), 6.52 (1H, brs; H4’), 6.39 (2H, d, J=
1.78 Hz; H1’, H6’), 3.88 (4H, t, J=6.52 Hz; OCH2), 2.68 (6H, s; CH3),
1.74–1.64 (4H, m; CH2), 1.69 (6H, s; CH3), 1.43–1.33 (4H, m; CH2), 1.20
(24H, s; CH2), 0.80 ppm (6H, t, J=5.26 Hz; CH3); 13C NMR (100 MHz,
CDCl3): d=161.4, 156.2, 155.9, 149.3, 149.1, 141.0, 137.7, 136.9, 132.1,
132.0, 131.9, 131.6, 131.1, 128,6, 128.4, 127.2, 124.2, 123.9, 121.4, 118.6,
106.2, 96.4, 83.0, 68.5, 31.9, 29.6, 29.4, 29.3, 29.2, 26.0, 22.7, 14.1,
13.9 ppm; HRMS (MALDI-TOF): m/z calcd for C85H85BF2N8O2:
1298.686 [M]+; found: 1298.830 [M]+.
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methyl-4’’-bora-3’’a,4’’a-diaza-s-indacene-2’’-ethynyl-2,2’-bipyridine
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3
CTHUNGTRENNUNG
(0.0265 mmol, 5.05 mg), and freshly distilled THF (10 mL) were added to
a 50 mL Schlenk tube. Diisopropylamine (5 mL) was added and the re-
sulting suspension was extensively deaerated by bubbling with argon at
508C for 40 min. After degassing, the reaction mixture was stirred at
508C for 1 d. After removal of the solvents under reduced pressure, the
residue was washed with water (100 mL) and extracted into CHCl3. The
organic layer was evaporated and separation by column chromatography
on silica gel using CHCl3 as the eluant gave 6 as a purple solid (0.215 g,
1
55%). H NMR (400 MHz, CDCl3): d=8.65 (2H, d, JH6ÀH4 =1.44 Hz; H6,
H6’), 8.28 (2H, d, JH3ÀH4 =8.28 Hz; H3, H3’), 7.73 (2H, dd, JH4ÀH3 =8.28,
J
H4ÀH6 =1.04 Hz; H4, H4’), 6.47 (2H, t, J=2.20 Hz; H4’’’), 6.32 (4H, d,
J=2.20 Hz; H2’’’, H6’’’), 5.98 (2H, s; H2’’), 3.82 (8H, t, J=6.62 Hz;
OCH2), 2.63 (6H, s; CH3), 2.50 (6H, s; CH3), 1.71–1.61 (8H, m; CH2),
1.60 (6H, s; CH3), 1.52 (6H, s; CH3), 1.38–1.29 (8H, m; CH2), 1.20 (48H,
brs; CH2), 0.78 ppm (12H, t, J=5.28 Hz; CH3); 13C NMR (100 MHz,
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Received: December 4, 2008
Published online: February 19, 2009
3838
www.chemeurj.org
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3830 – 3838