Soluble phosphorescent iridium(iii) complexes from cinchonine-derived ligands

Article abstract of DOI:10.1021/om200759d

Cinchonine-derived complexes Ir(L2)₂(acac) (3), Ir(L2) ₂(dbm) (4), [Ir-(L1)2(bipy)][PF6] (5), [Ir(L1)2(phen)][PF6] (6), [Ir(L1)2(dppe)][PF6] (7), [Ir-(L2)₂(bipy)][PF6] (8), [Ir(L2) ₂(phen)][PF6] (9), and [Ir(L2)

Full text of DOI:10.1021/om200759d

Article
pubs.acs.org/Organometallics
Soluble Phosphorescent Iridium(III) Complexes from Cinchonine-
Derived Ligands
Wen-Hua Zhang,†,‡ Xin-Hai Zhang,‡ Ai Ling Tan,§ M. Anna Yong,‡ David J. Young,*,§
and T. S. Andy Hor*,†,‡
†Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543 Singapore
‡Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 3 Research Link, 117602 Singapore
§Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE 1410, Brunei Darussalam
S
* Supporting Information
ABSTRACT: Cinchonine-derived complexes Ir(L2)2(acac) (3), Ir(L2)2(dbm) (4), [Ir-
(L1)2(bipy)][PF6] (5), [Ir(L1)2(phen)][PF6] (6), [Ir(L1)2(dppe)][PF6] (7), [Ir-
(L2)2(bipy)][PF6] (8), [Ir(L2)2(phen)][PF6] (9), and [Ir(L2)2(dppe)][PF6] (10) (L1 =
2′-phenyl-9-O-benzyl-10,11-dihydrocinchonine-N,C; L2 = 2′-(2,4-difluorophenyl)-9-O-ben-
zyl-10,11-dihydrocinchonine-N,C; acac = acetylacetonate; dbm = dibenzoylmethane; bipy =
2,2′-bipyridine; phen = 1,10-phenanthroline; dppe = (Z)-1,2-bis(diphenylphosphino)ethene)
are highly soluble in common organic solvents and phosphoresce with emission wavelengths
from orange to green (583−529 nm) and internal quantum efficiencies from 4 to 24%. The
emission is blue-shifted for the neutral auxiliary ligands and/or by incorporation of fluorine
into the alkaloid-based chromophore. An unprecedented regiospecific monohydrodefluori-
nation of L2, giving 2′-(4-fluorophenyl)-9-O-benzyl-10,11-dihydrocinchonine (L2′), occurred
during the synthesis of 3 and 4.
Chart 1
INTRODUCTION
■
Third-row transition metal based phosphors have been
developed for organic light-emitting diodes (OLEDs) and
light-emitting electrochemical cells (LECs) because of the
spin−orbit interaction that allows spin-forbidden electronic
transitions and thereby higher quantum efficiencies in these
organometallic complexes.1−3 Well-studied examples include
Ir(ppy)3 (ppy = 2-phenylpyridinato-C2,N), Ir(ppz)3 (ppz = 1-
phenylpyrazolato-N,C2′), and Ir(pmi)3 (pmi = 1-phenyl-3-
methylimidazolin-2-ylidene-C,C2′) (Chart 1) and their deriva-
tives, which exhibit a wide range of emission colors. Ligands
with dendritic peripheries reduce triplet−triplet annihilation of
the emissive iridium cores, improve processability, and avoid
the necessity of a polymer host.1d,4,5 We have recently reported
that, with relatively straightforward synthetic modifications,
Cinchona alkaloid derivatives (Chart 1) function as novel
cyclometalating and coordinating ligands for phosphorescent
iridium complexes.6 The bulky 1-azabicyclo[2.2.2]octane and
benzyl moieties impart higher quantum efficiencies to the
resulting bis-cyclometalated complexes relative to simple
quinoline congeners, thereby serving a similar, albeit reduced,
function relative to more elaborate dendritic ligands.4,5
In an attempt to improve solubility and broaden the range of
emissive wavelengths of these compounds, we have prepared
the dinuclear complexes [Ir(L1)2Cl]2 (1) and fluorinated
analogue [Ir(L2)2Cl]2 (2) and reacted them with a series of
neutral and anionic auxiliary ligands to yield the corresponding
cationic and neutral heteroleptic mononuclear complexes. In
some cases the reaction of these alkaloid-based complexes leads
Received: August 13, 2011
Published: December 30, 2011
© 2011 American Chemical Society
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Scheme 1. Synthesis of Complexes 3 and 4
Scheme 2. Reaction of 1 and 2 with 2-Phenylpyridine (ppy)
to an unexpected hydrodefluorination. Herein we report the
improved solubility and blue shift of emission for a series of
eight new Cinchonine-based mononuclear Ir(III) complexes.
Heating a mixture of 1, ppy, and K2CO3 in 2-ethoxyethanol
at 90 °C for 12 h resulted in none of the anticipated product
with ca. 90% of the starting material recycled (Scheme 2). At a
higher temperature (130 °C), the starting material 1 partially
decomposed and liberated the free ligand L1 (Scheme 2). The
corresponding reaction of 2 with ppy at 90 °C also resulted in
none of the expected product. However, when the reaction was
carried out at 130 °C, L2′ was formed in 21% isolated yield and
the liberation of L2 was not observed (Scheme 2). The
formation of mixed-chelate complexes 3 and 4 (Scheme 1) is
driven by displacement of HCl and stable chelate formation.
The absence of [Ir(L)2(ppy)] (L = L1, L2) can be explained by
the nature of ppy, which is a monodentate ligand but can serve
as a chelating ligand upon an energetically demanding C−H
activation.
More interestingly, however, is the regiospecific monohy-
drodefluorination of coordinated L2 to L2′ (Scheme 1). The
C−F bond is the strongest single bond connected to carbon,8
and dehydrofluorination9 usually requires either a reactive
substrate10 and/or a highly reducing, electron-rich metal (e.g.
low-valent niobium11) reacting through an oxidative-addition or
a single-electron-transfer step or a Lewis acid abstraction of
fluoride by a highly electrophilic silylium cation.12 The
iridium(I)-mediated cleavage of hexafluorobenzene with
(Et3P)3IrMe to yield the unusual (Et2FP)(Et3P)2IrC6F5 with
evolution of methane most likely proceeds via an electron-
transfer process.13 We are unaware of any reports of Ir(III)-
mediated hydrodefluorination, although a Rh(III) catalyst
generated from [(Cy3P)2Rh(H)Cl2], molecular hydrogen, and
base (in the absence of oxygen) efficiently hydrodefluorinates
RESULTS AND DISCUSSION
■
Dinuclear complexes 1 and 2 were synthesized by the well-
established Nonoyama method7 of heating a mixture of
IrCl3·xH2O with 3 equiv of L1 or L2 in 2-ethoxyethanol/
water (3/1 v/v) under an inert atmosphere. During the
preparation of 2, a trace amount of a hydrodefluorinated Ir(III)
complex was also observed in the ESI mass spectrum. A
molecular ion of m/z 1169.5 corresponds to the substitution of
a proton for one fluorine atom in [Ir(L2)2]+ (m/z 1187.5). The
facile reaction of 1 and ancillary ligands acetylacetone (acacH)
and dibenzoylmethane (dbm) in the presence of base yielded
the two targeted neutral complexes Ir(L1)2(acac) and
Ir(L1)2(dbm) in high yield.6 Analogous reactions of 2 also
yielded the target complexes Ir(L2)2(acac) (3) and Ir-
(L2)2(dbm) (4) (Scheme 1). In the preparation of 3 and 4,
however, the regiospecific formation of the hydrodefluorinated
ligand 2′-(4-fluorophenyl)-9-O-benzyl-10,11-dihydrocinchonine
(L2′) was observed as a side product (Scheme 1). The
proportion of L2′ correlated with the reaction temperature. At
an elevated temperature of 120 °C, L2′ was isolated in ca. 20%
yield for both reactions, while 3 and 4 were only formed in
trace amounts. However, at 80 °C, complexes 3 and 4 were
isolated in moderate yield (58% and 45%, respectively).
Motivated by these observations, we further scrutinized the
reactivity of 1 and 2 toward 2-phenylpyridine (ppy), which is
often utilized to form cyclometalated Ir(III) complexes.
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a
Scheme 3. Proposed Hydrodefluorination Mechanism
a
The quinuclidine moiety on C4 is omitted for clarity.
Scheme 4. Synthesis of Complexes 5−10
some unreactive monofluoroarenes such as 1-fluoronaphtha-
lene to yield naphthalene.14 A possible mechanism in the
present case is the formation of a hydrido iridium species by
hydrogen transfer15 from solvent (ethoxyethanol) followed by
reductive elimination and iridium insertion into the C−F bond
of the cyclometalated ligand (Scheme 3).
ppm.16 Complexes 3−10 were further characterized by FT-IR
spectra and their bulk purity confirmed by elemental analysis.
The UV−vis absorption and emission data for complexes 3−
10 are given in Figures 1−3 and Table 1. The intense bands in
Treatment of 1 or 2 with the neutral chelating ligands 2,2′-
bipyridine (bipy), 1,10-phenanthroline (phen), and (Z)-1,2-
bis(diphenylphosphino)ethene (dppe) in refluxing CH2Cl2/
MeOH (2/1 v/v) followed by anion exchange with excess
NH4PF6 at room temperature yielded the six ionic complexes
[Ir(L1)2(bipy)][PF6] (5), [Ir(L1)2(phen)][PF6] (6), [Ir-
(L1)2(dppe)][PF6] (7), [Ir(L2)2(bipy)][PF6] (8), [Ir-
(L2)2(phen)][PF6] (9), and [Ir(L2)2(dppe)][PF6] (10),
which were separated by chromatography on neutral alumina
in moderate to high yields (Scheme 4).
These complexes (3−10) are highly soluble in CH2Cl2,
DMF, and DMSO and readily soluble in CHCl3, MeCN,
MeOH, and toluene. Molecular ions [M + H]+ (neutral
complexes) and [M − PF6]+ (charged complexes) were
observed in the ESI mass spectra at m/z 1286.9 (3), 1411.1
(4), 1271.5 (5), 1295.5 (6), 1511.4 (7), 1343.4 (8), 1367.5 (9),
and 1583.5 (10). The corresponding cationic fragments
[Ir(L1)2]+ and [Ir(L2)2]+ (3−10) and dicationic species [M
+ 2H]2+ (3, 4) and [Ir(L1)2 + H]2+ and [Ir(L2)2 + H]2+ (5−
Figure 1. UV−vis spectra of 3−10 recorded in degassed CH2Cl2
solutions at room temperature.
the UV−vis spectra for all complexes in the high-energy portion
of the spectra between 230 and 350 nm can be assigned to the
spin-allowed 1(π−π*) ligand transition. The weaker, low-
energy bands at wavelengths longer than 440 nm suggests
1
10) were also observed. H and 13C NMR spectra for these
complexes were rather complex, but the protons ortho to the
cyclometalated carbon appeared characteristically at ca. 6.5
3
substantial mixing of spin-forbidden MLCT and higher lying
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Table 1. Photophysical Data for 3−10 in Degassed CH2Cl2
at Room Temperature
λmax
(nm)
a
UV−vis (nm) (ε, 103 L mol−1 cm−1)
Φ
τ (μs)
3
4
5
6
7
8
9
228 (100.0), 277 (98.6), 345 (40.9),
411 (12.4), 469 (8.5)
580
0.10
0.30
226 (68.0), 272 (86.0), 334 (37.4),
451 (8.6), 483 (3.9)
583
567
564
531
551
552
529
0.05
0.23
0.24
0.04
0.14
0.13
0.04
0.26
0.63
0.46
0.73
0.38
0.43
0.53
233 (81.1), 284 (92.9), 344 (36.4),
422 (45.6)
228 (83.7), 268 (77.5), 338 (31.4),
442 (7.1)
227 (106.0), 282 (61.3), 341 (27.1),
408 (10.9)
228 (61.6), 249 (61.3), 283 (56.1),
343 (28.5), 426 (7.4)
229 (65.3), 267 (47.9), 353 (17.8),
423 (5.5)
Figure 2. Normalized luminescence spectra of 3−10 recorded in
degassed CH2Cl2 solutions at room temperature.
10 229 (87.5), 284 (46.9), 351 (21.1),
398 (9.7)
a
With respect to Rhodamine 6G (Φ = 0.95 in ethanol).
1MLCT transitions facilitated by the strong spin−orbit coupling
of the Ir(III) center.17
The introduction of two fluorine atoms on the 2,4-position
Complexes 3−10 give emissions in a broad color range from
green (529 nm, 10) to orange-red (583 nm, 4) (Figure 3) with
phosphorescence quantum yields between 0.04 and 0.24 and
lifetimes in the range 0.26−0.73 μs. The quantum yields for
these complexes are relatively low compared to those of well-
established examples such as Ir(ppy)2(acac) (0.34, 2-MeTHF
solution, room temperature),17a fac-Ir(ppy)3 (0.40, 2-MeTHF
solution, room temperature),17b [(dfbmb)2Ir(fptz)] (0.73,
CH2Cl2, room temperature; dfbmb = 1-(2,4-difluorobenzyl)-
3-methylbenzimidazolium; fptz = 2-(5-(trifluoromethyl)-2H-
1,2,4-triazol-3-yl)pyridine),17e and the dendrimer complex fac-
tris[1-methyl-5-(4-fluorophenyl)-3-n-propyl-1H-[1,2,4]-
triazolyl]iridium(III) (0.94, toluene, room temperature).4b The
lifetimes of complexes 3−10 are, however, very short and are
similar to those found in mer-Ir(ppy)3 (0.15 μs, CH2Cl2, room
temperature),17b mer-Ir(46dfppy)3 (0.21 μs, CH2Cl2, room
temperature; 46dfppy = 2-(4,6-difluorophenyl)pyridinato-
N,C2′),17b fac-Ir(tiq)3 (0.74 μs, toluene, room temperature; tiq
= 1-thiophen-2-ylisoquinolinato-C3,N),17c and [(dfbmb)2Ir-
(fptz)] (0.38 μs, CH2Cl2, room temperature)17e and are
shorter than those of fac-tris[1-methyl-5-(4-fluorophenyl)-3-n-
propyl-1H-[1,2,4]triazolyl]iridium(III) (3.6 μs, toluene, room
temperature),4b and fac-tris[5-(4-fluorophenyl)-1-methyl-3-
propyl-[1,2,4]-triazolyl]iridium(III) (1.25 μs, toluene, room
temperature).4g
of the phenyl ring stabilizes the energy of the HOMO orbitals,
resulting in a blue shift of 3 (580 nm) and 4 (583 nm)
compared to Ir(L1)2(acac) (597 nm) and Ir(L1)2(dbm) (608
nm).6 The triplet energy levels of the acac of complex 3 lie
above the energies of L2 and MLCT excited states, and the
luminescence is thus dominated by L2 and MLCT transitions.
The slightly longer emission wavelength and relatively low
quantum efficiency of complex 4 can be attributed to the lower
triplet-state energy of dbm relative to L2 or the 1MLCT in this
complex. The emission wavelengths of 5 (567 nm) and 6 (564
nm) are further blue-shifted relative to those of 3 and 4,
suggesting that, for these cationic Ir(III) complexes, the
HOMO consists mainly of a mixture of Ir d and phenyl π
orbitals, while the LUMO has significant chelating ligand
character. Such an explanation is further supported by the
observation that using the higher triplet energy dppe as the
chelating ligand results in a more significant blue shift to 531
nm (7). Not surprisingly, the use of auxiliary ligands bipy and
phen in complexes 5 and 6 resulted in similar emission
wavelengths and quantum yields. The contribution of two
fluorine atoms at the 2,4-position of the phenyl ring blue-
shifted the phosphorescence wavelength by 2−16 nm (Table
1).
Figure 3. Emission of 3−10 recorded in degassed CH2Cl2 solutions at room temperature excited at 365 nm.
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7.33 (m, 1H), 7.19−7.22 (m, 2H), 5.40 (br, 1H), 4.46−4.52 (AB
quartet, 2H), 3.47−3.73 (m, 1H), 3.06−3.10 (m, 2H), 2.88−2.93 (m,
1H), 2.81−2.85 (m, 1H), 2.69−2.75 (m, 1H), 2.07−2.12 (m, 1H),
1.69 (br, 1H), 1.40−1.50 (m, 5H), 1.20−1.29 (m, 3H), 0.89 (t, J = 7.0
Hz, 3H) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ 164.8, 162.8,
155.9, 148.8, 147.5, 138.0, 136.0, 136.0, 130.7, 129.5, 129.4, 129.4,
128.5, 128.3, 128.0, 127.9, 127.8, 126.4, 125.6, 123.1, 115.8, 115.7,
71.7, 60.7, 51.1, 50.3, 37.6, 27.4, 26.5, 25.4, 12.0 ppm. 19F{1H} NMR
(282 MHz, CDCl3): δ −36.4 ppm. MS (ESI): m/z 481.3 [M + H]+.
Synthesis of 4. Complex 4 was synthesized using the same
procedure described for 3. The crude product was purified by
chromatography on neutral Al2O3 using ethyl acetate as eluent. Yield:
0.13 g (45% based on Ir). 1H NMR (500 MHz, CD2Cl2): δ 8.71−8.75
(m, 2H), 8.47−8.48 (m, 2H), 8.12 (br, 2H), 7.15−7.50 (m, 25H),
6.59−6.64 (m, 2H), 6.27−6.29 (m, 1H), 5.91−5.94 (m, 1H), 5.34−
5.42 (m, 3H), 4.28−4.63 (m, 5H), 2.61−3.25 (m, 11H), 1.97−2.19
(m, 3H), 1.77 (br, 1H), 1.12−1.63 (m, 25H), 0.90−0.97 (m, 12H)
ppm. 13C{1H} NMR (125 MHz, CD2Cl2): δ 180.9, 180.6, 166.7 (m),
163.4, 163.3, 162.9, 162.8, 161.4, 161.3, 160.8, 160.7, 153.6, 153.5,
150.7, 150.2, 148.8, 148.7, 140.5, 140.4, 138.0, 131.7, 130.2, 130.2,
128.4, 128.3, 128.3, 128.1, 128.1, 128.0, 127.7, 126.9, 127.4, 126.3,
126.1, 125.1, 123.7, 117.9 (br), 97.7, 94.6, 71.9, 71.4, 61.4, 60.9, 50.9,
50.1, 50.0, 37.7, 37.7, 29.7, 27.4, 26.7, 26.6, 25.3, 11.8 ppm. 19F NMR
(282 MHz, CD2Cl2): δ −34.3 to −34.2 (m) ppm. MS (ESI): m/z
706.5 [M + 2H]2+; 1187.5 [Ir(L2)2]+; 1411.1 [M + H]+. Anal. Calcd
for C79H73F4IrN4O4: C, 67.26; H, 5.22; N, 3.97. Found: C, 67.14; H,
5.34; N, 3.73. IR (KBr pellet): 3063 (w), 2955 (m), 2932 (m), 2869
(w), 2037 (m), 1598 (s), 1575 (m), 1544 (m), 1518 (w), 1455 (w),
1424 (w), 1402 (w), 1359 (w), 1326 (w), 1287 (w), 1251 (w), 1199
(w), 1159 (w), 1106 (m), 1059 (w), 1024 (w), 988 (m), 936 (w), 839
(m), 758 (m), 699 (m), 611 (w), 529 (w) cm−1.
CONCLUSION
■
We have prepared two neutral and six ionic Ir(III)
phosphorescent complexes from alkaloid-derived ligands.
These complexes phosphoresce at wavelengths from orange
to green with internal quantum efficiencies from 0.04 to 0.24.
The extra functionality of the natural products enables the
resultant cationic complexes to be dissolved in a range of
common organic solvents. In this respect, it serves a similar
function to the elaborate dendrimer architectures of Burn and
co-workers.4 This enhanced solubility has prompted us to
investigate their potential advantages in device fabrication. The
unusual regiospecific monohydrodefluorination suggests the
possibility of Ir(III)-catalyzed C−F activation, and we are
investigating the mechanism and scope of this reaction.
EXPERIMENTAL SECTION
■
All synthetic procedures involving IrCl3·xH2O and other Ir(III) species
were carried out in the dark and under a N2 atmosphere using standard
Schlenk techniques. Elemental analyses were performed on a Perkin−
Elmer PE 2400 CHNS Elemental Analyzer. The H and 13C NMR
1
spectra were recorded on a Bruker AMX 500 MHz spectrometer, and
their chemical shifts were referenced to Me4Si (TMS). The 19F NMR
spectra were recorded on a Bruker ACF 300 spectrometer. IR spectra
were recorded on a Bruker IFS 48 FTIR spectrometer using KBr
pellets. UV−vis spectra were recorded on a UVIKON spectrometer.
Electrospray mass spectra were obtained in positive ion mode with a
Finnigan/MAT LCQ mass spectrometer. Peaks were assigned from
the m/z values and the isotope distribution patterns. Photo-
luminescence was measured using a Perkin-Elmer LS55 luminescence
spectrometer, and the quantum yield was determined using Rhod-
amine 6G (quantum yield 0.96 in ethanol) as reference.18 The
phosphorescence lifetime was measured using an Edinburgh FL920P
Lifetime Spectrometer.
Synthesis of 3. A mixture of 2 (0.25 g, 0.1 mmol), acetylacetone
(0.025 g, 0.25 mmol), and K2CO3 (0.14 g, 1 mmol) were dissolved in
2-ethoxyethanol (5 mL), which was then degassed, flushed three times
with N2, and heated to 80 °C for 8 h. The mixture was then cooled to
room temperature, the solvent was removed in vacuo, and CH2Cl2 (50
mL) was added. The organic phase was washed with brine (3 × 50
mL) and dried over anhydrous Na2SO4. The solvent was removed and
the crude product was dried under vacuum and purified by
chromatography on a neutral Al2O3 column using ethyl acetate/
MeOH (10/1 v/v) as eluent to give an orange-red solid (3). Yield:
Synthesis of 5. A mixture of 1 (0.23 g, 0.1 mmol) and 2,2′-
bipyridine (0.032 g, 0.21 mmol) in a double-necked flask was flushed
three times with N2. A CH2Cl2/MeOH mixture (20 mL/10 mL) was
added under N2, and the mixture was heated to reflux for 12 h. The
mixture was cooled to room temperature, and NH4PF6 (0.16 g, 1.0
mmol) in MeOH (5 mL) was added under N2. The mixture was
stirred for another 5 h and the solvent evaporated. The resulting
orange-red residue was dried under vacuum, and CH2Cl2 (5 mL) was
added. NH4Cl was removed by filtration. The solvent was removed
and the product purified by chromatography on neutral Al2O3 column
using ethyl acetate/MeOH (30/1 v/v) as eluent to give an orange-red
solid. Yield: 0.18 g (63.5% based on Ir). 1H NMR (500 MHz,
CD2Cl2): δ 8.26−8.34 (m, 2H), 8.01−8.13 (m, 3H), 7.91−7.94 (m,
1H), 7.36−7.46 (m, 8H), 7.23−7.27 (m, 1H), 6.98−7.03 (m, 1H),
6.91−6.94 (m, 1H), 6.69−6.73 (m, 1H), 5.36 (s, 1H), 4.54−4.59 (m,
1H), 4.38−4.45 (m, 1H), 3.00−3.01 (m, 1H), 2.74−2.88 (m, 2H),
2.61−2.64 (m, 2H), 1.96−2.00 (m, 1H), 1.76−1.78 (m, 2H), 1.45−
1.52 (m, 5H), 1.25−1.31 (m, 2H), 0.91−0.97 (m, 4H) ppm. 13C{1H}
NMR (125 MHz, CD2Cl2): δ 169.0, 155.5, 152.1, 152.0, 150.5, 150.4,
147.7, 147.6, 147.3, 146.0, 139.1, 137.7, 134.8, 134.8, 130.6, 130.3,
130.3, 128.5, 128.2, 128.0, 127.9, 127.4, 127.1, 126.6, 125.6, 125.5,
124.9, 124.7, 123.8, 123.7, 123.0, 72.2, 71.7, 61.6, 61.6, 50.9, 50.9, 50.1,
49.9, 37.6, 37.5, 27.4, 27.4, 26.4, 26.4, 25.4, 25.3, 11.8 ppm. MS (ESI;
CH2Cl2, 180 °C): m/z 558 [Ir(L1)2 + H]2+; 636.6 [Ir(L1)2(bipy) +
H]2+; 1115.6 [Ir(L1)2]+; 1271.5 [Ir(L1)2(bipy)]+. Anal. Calcd for
C74H74F6IrN6O2P: C, 62.74; H, 5.27; N, 5.93; found: C, 62.61; H,
5.50; N, 5.64. IR (KBr pellet): 3032 (w), 2930 (m), 2863 (w), 1601
(s), 1581 (m), 1541 (m), 1515 (w), 1451 (m), 1367 (m), 1314 (w),
1288 (w), 1203 (w), 1162 (w), 1114 (w), 1066 (w), 1028 (w), 939
(w), 841 (s), 764 (m), 736 (w), 699 (m), 612 (w), 557 (m) cm−1.
Synthesis of 6. Complex 6 was synthesized using the same
procedure described for 5. The crude product was purified by
chromatography on neutral Al2O3 using ethyl acetate/MeOH (8/1 v/
1
0.15 g (58% based on Ir). H NMR (500 MHz, CD2Cl2): δ 8.69 (br,
1H), 8.62 (br, 1H), 8.38−8.41 (m, 2H), 8.20−8.34 (m, 3H), 7.36−
7.62 (m, 18H), 6.53−6.58 (m, 2H), 6.15−6.17 (m, 2H), 5.48 (br, 1H),
4.49−4.74 (m, 6H), 3.34−3.38 (m, 1H), 3.19−3.20 (m, 1H), 2.65−
3.01 (m, 11H), 1.98−2.12 (m, 5H), 1.75−1.79 (m, 3H), 1.31−1.64
(m, 28H), 0.91−0.95 (m, 10H) ppm. 13C{1H} NMR (125 MHz,
CD2Cl2): δ 186.1, 185.9, 166.8, 163.3 (d, JC−F = 15.0 Hz), 162.7 (d,
JC−F = 13.9 Hz), 161.3 (d, JC−F = 15.2 Hz), 160.6 (d, JC−F = 14.1 Hz),
153.4, 153.4, 153.3, 150.5, 150.2, 148.8, 148.7, 137.9, 131.7, 131.7,
130.2, 130.1, 128.3, 128.3, 128.1, 127.8, 127.8, 126.8, 126.8, 126.3,
126.2, 125.5, 123.6, 118.1, 118.1, 117.9, 100.1, 100.0, 97.8, 97.6, 97.4,
71.9, 71.6, 61.4, 61.1, 50.9, 50.7, 50.1, 50.0, 37.7, 37.6, 27.8, 27.7, 27.5,
27.5, 26.6, 26.5, 25.4, 25.3, 11.8 ppm. 19F NMR (282 MHz, CD2Cl2):
δ −34.14 ppm. MS (ESI; CH2Cl2, 180 °C): m/z 644.2 [M + 2H]2+;
1187.5 [Ir(L2)2]+; 1286.9 [M + H]+. Anal. Calcd for C69H69F4IrN4O4:
C, 64.42; H, 5.41; N, 4.35. Found: C, 63.76; H, 5.89; N, 4.03. IR (KBr
pellet): 3067 (w), 3030 (w), 2932 (s), 2865 (m), 2038 (w), 1599 (s),
1581 (s), 1543 (m), 1516 (m), 1499 (w), 1453 (m), 1397 (m), 1360
(w), 1325 (w), 1287 (w), 1250 (w), 1201 (w), 1158 (m), 1104 (s),
1067 (w), 1042 (w), 1025 (w), 988 (s), 935 (w), 853 (m), 833 (m),
760 (m), 698 (m), 611 (w), 588 (w), 530 (w), 519 (w), 497 (w), 424
(w) cm−1.
1
v) as eluent. Yield: 0.21 g (72.9% based on Ir). H NMR (500 MHz,
CD2Cl2): δ 8.61−8.63 (m, 2H), 8.45−8.47 (m, 2H), 8.32−8.38 (m,
2H), 8.14−8.19 (m, 2H), 7.99−8.01 (m, 1H), 7.88−7.93 (m, 3H),
7.81−7.84 (m, 1H), 7.73−7.76 (m, 1H), 7.21−7.46 (m, 15H), 6.96−
6.99 (m, 2H), 6.75−6.84 (m, 4H), 5.36 (s, 1H), 5.17−5.18 (m, 1H),
4.54 (s, 2H), 4.35−4.42 (m, 2H), 3.13−3.18 (m, 1H), 2.94−2.96 (m,
1
Characterization data for L2′ are as follows. H NMR (500 MHz,
CDCl3): δ 8.22 (d, J = 8.2 Hz, 1H), 8.15−8.18 (m, 2H), 7.97 (s, 1H),
7.72−7.75 (m, 1H), 7.54−7.58 (m, 1H), 7.35−7.38 (m, 4H), 7.30−
557
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Organometallics
Article
1H), 2.76−2.89 (m, 4H), 2.58−2.63 (m, 4H), 1.96−2.02 (m, 5H),
1.75 (br, 2H), 1.56−1.62 (m, 2H), 1.46−1.52 (m, 9H), 0.92−0.96 (m,
6H) ppm. 13C{1H} NMR (125 MHz, CD2Cl2): δ 169.1, 151.8, 150.3,
150.2, 150.1, 148.1, 147.6, 146.8, 146.7, 146.2, 138.3, 138.2, 137.7,
137.7, 135.9, 135.2, 135.1, 130.8, 130.7, 130.7, 130.6, 130.0, 130.0,
128.5, 128.5, 128.2, 128.0, 127.9, 127.9, 127.9, 127.2, 127.1, 126.6,
126.5, 126.3, 126.3, 126.1, 125.9, 125.0, 125.0, 124.8, 124.5, 123.1,
123.0, 72.1, 71.7, 61.4, 50.8, 50.0, 49.9, 37.6, 37.5, 27.4, 27.3, 26.4,
26.4, 25.3, 25.3, 11.8 ppm. MS (ESI; CH2Cl2, 180 °C): m/z 648.5
[Ir(L1)2(phen) + H]2+; 1115.6 [Ir(L1)2]+; 1295.5 [Ir(L1)2(phen)]+.
Anal. Calcd for C76H74F6IrN6O2P: C, 63.36; H, 5.18; N, 5.83. Found:
C, 62.78; H, 5.28; N, 5.63. IR (KBr pellet): 3057 (w), 2930 (m), 2863
(w), 1601 (s), 1580 (m), 1541 (m), 1515 (w), 1453 (m), 1429 (w),
1366 (m), 1288 (w), 1260 (w), 1224 (w), 1204 (w), 1162 (m), 1112
(w), 1028 (w), 939 (m), 841 (s), 764 (w), 726 (m), 699 (m), 613 (w),
557 (m) cm−1.
2H), 7.68−7.70 (m, 2H), 7.22−7.52 (m, 25H), 6.78−6.88 (m, 6H),
6.39−6.42 (m, 2H), 5.36 (br, 2H), 5.16−5.22 (m, 1H), 4.54 (br, 3H),
4.32−4.43 (m, 3H), 3.10−3.15 (m, 1H), 2.76−2.90 (m, 8H), 2.34−
2.40 (m, 16H), 1.94−1.98 (m, 3H), 1.76 (br, 3H), 1.19−1.64 (m,
43H), 0.74−0.97 (m, 23H) ppm. 13C{1H} NMR (125 MHz, CD2Cl2):
δ 166.2, 166.2, 164.7, 164.6, 163.6, 163.3, 162.6, 162.5, 161.5, 161.4,
153.0, 152.9, 152.9, 152.6, 152.5, 150.0, 148.1, 148.0, 147.5, 147.4,
146.5, 146.4, 146.3, 139.0, 138.9, 137.6, 137.5, 136.0, 130.9, 130.8,
130.3, 128.8, 128.5, 128.4, 128.3, 128.2, 128.2, 128.1, 128.0, 128.0,
128.0, 127.9, 126.9, 126.8, 126.6, 126.1, 126.1, 125.8, 125.6, 125.0,
124.8, 124.7, 124.6, 123.0, 117.7, 117.6, 99.8 (m), 72.3, 71.7, 61.3,
61.0, 50.7, 50.6, 50.0, 49.8, 37.5, 37.3, 32.0, 29.7, 29.4, 29.1, 27.2, 27.1,
26.4, 25.3, 25.3, 25.3, 23.0, 22.7, 13.9, 11.8, 11.7 ppm. 19F NMR (282
MHz, CD2Cl2): δ 3.45 (s), 0.94 (s), −30.29−(−31.94) (m) ppm. MS
(ESI; CH2Cl2, 180 °C): m/z 684.5 [Ir(L2)2(phen) + H]2+; 1367.5
[Ir(L2)2(phen)]+. Anal. Calcd for C76H70F10IrN6O2P: C, 60.35; H,
4.66; N, 5.56. Found: C, 62.73; H, 5.24; N, 5.40. IR (KBr pellet): 2928
(s), 2858 (m), 1735 (w), 1599 (s), 1574 (m), 1543 (s), 1515 (w),
1499 (w), 1455 (m), 1414 (m), 1360 (m), 1325 (w), 1289 (m), 1254
(m), 1227 (w), 1200 (w), 1162 (m), 1108 (s), 1026 (w), 991 (s), 938
(w), 909 (w), 841 (s), 760 (w), 726 (m), 699 (w), 613 (w), 557 (m),
530 (w), 495 (w), 439 (w) cm−1.
Synthesis of 7. Complex 7 was synthesized using the same
procedure described for 5. The crude product was purified by
chromatography on neutral Al2O3 using ethyl acetate/MeOH (25/1 v/
1
v) as eluent. Yield: 0.08 g (24.1% based on Ir). H NMR (500 MHz,
CD2Cl2): δ 8.95−9.06 (m, 1H), 7.87−7.95 (m, 3H), 7.59−7.68 (m,
3H), 7.19−7.48 (m, 12H), 6.90−6.92 (m, 1H), 6.50−6.59 (m, 6H),
5.84−5.86 (m, 1H), 5.16 (br, 1H), 4.37−4.43 (m, 2H), 2.66−2.99 (m,
5H), 1.95−2.04 (m, 2H), 1.73−1.78 (m, 1H), 1.26−1.57 (m, 11H),
0.85−0.94 (m, 6H) ppm. 13C{1H} NMR (125 MHz, CD2Cl2): δ
170.4, 157.1, 156.4, 151.1, 149.7, 149.7, 149.4, 149.2, 147.1, 145.2,
137.5, 135.0, 134.7, 133.2, 133.2, 132.2, 132.2, 132.2, 132.1, 130.9,
130.7, 129.6, 129.5, 128.9, 128.8, 128.5, 128.2, 128.0, 127.0, 126.9,
126.8, 126.8, 125.9, 124.2, 124.1, 71.9, 60.8, 50.7, 50.0, 37.6, 29.7, 27.7,
26.6, 25.4, 11.8, 11.8 ppm. 31P{1H} NMR (202 MHz, CD2Cl2): δ 11.1,
−143.7 (hept) ppm. MS (ESI; CH2Cl2, 180 °C): m/z 756.6
[Ir(L1)2(dppe) + H]2+; 1511.4 [Ir(L1)2(dppe)]+. Anal. Calcd for
C90H88F6IrN4O2P3: C, 65.24; H, 5.35; N, 3.38. Found: C, 65.04; H,
5.53; N, 3.12. IR (KBr pellet): 3054 (w), 2928 (s), 2859 (m), 1720
(w), 1607 (s), 1579 (m), 1544 (s), 1519 (w), 1454 (m), 1434 (m),
1368 (m), 1291 (w), 1261 (w), 1214 (w), 1162 (w), 1098 (m), 1067
(w), 1026 (w), 998 (m), 937 (w), 840 (s), 747 (s), 736 (s), 696 (s),
612 (w), 555 (s), 526 (w), 504 (w), 474 (w) cm−1.
Synthesis of 10. Complex 10 was synthesized using the same
procedure described for 5. The crude product was purified by
chromatography on neutral Al2O3 using ethyl acetate/MeOH (25/1 v/
1
v) as eluent. Yield: 0.035 g (10% based on Ir). H NMR (500 MHz,
CD2Cl2): δ 9.13−9.15 (m, 1H), 9.05−9.06 (m, 1H), 8.54 (br, 1H),
8.42 (br, 1H), 7.82−8.01 (m, 3H), 7.55−7.75 (m, 8H), 7.26−7.48 (m,
24H), 6.52−6.76 (m, 14H), 5.10−5.26 (m, 4H), 4.36−4.47 (m, 4H),
2.63−3.03 (m, 11H), 1.90−2.01 (m, 2H), 1.73−1.77 (m, 2H), 1.33−
1.57 (m, 17H), 0.88−0.93 (m, 9H) ppm. 13C{1H} NMR (125 MHz,
CD2Cl2): δ 167.7 (br), 164.3 (br), 163.3 (br), 162.3 (br), 161.2 (br),
160.2 (br), 159.8 (br), 159.4 (br), 159.1 (br), 159.8, 159.4, 159.1,
152.4, 152.2, 149.5, 149.3, 149.0, 149.0, 144.9, 144.8, 143.7, 143.7,
142.9, 142.9, 137.5, 137.5, 134.2, 133.8, 133.8, 132.3, 132.2, 132.2,
131.9, 131.9, 131.8, 131.2, 131.2, 131.1, 131.0, 129.5, 129.5, 129.4,
129.3, 129.2, 129.1, 129.1, 128.5, 128.4, 128.0, 128.0, 127.4, 127.2,
127.1, 127.0, 126.9, 125.8, 125.6, 124.2, 123.9, 115.7, 115.5, 115.3,
115.1, 100.9, 100.7, 100.4, 71.7, 71.6, 61.3, 61.0, 60.2, 50.8, 50.5, 50.0,
49.8, 37.5, 37.5, 29.7, 29.1, 27.6, 27.3, 26.6, 26.5, 25.3, 25.3, 20.8, 14.0,
11.8, 11.7, 11.7 ppm. 31P{1H} NMR (202 MHz, CD2Cl2): δ 19.3, 12.0,
11.3, −143.6 (hept) ppm. 19F NMR (282 MHz, CD2Cl2): δ 3.91, 1.39,
−29.27 (br), −31.1 (br) ppm. MS (ESI; CH2Cl2, 180 °C): m/z 792.6
[Ir(L2)2(dppe) + H]2+; 1583.5 [Ir(L2)2(dppe)]+. Anal. Calcd for
C90H84F10IrN4O2P3: C, 62.53; H, 4.90; N, 3.24. Found: C, 62.33; H,
4.87; N, 3.04. IR (KBr pellet): 3057 (w), 2932 (m), 2867 (w), 2038
(m), 1596 (s), 1579 (m), 1546 (m), 1519 (w), 1484 (w), 1453 (w),
1436 (m), 1412 (m), 1361 (m), 1288 (w), 1257 (w), 1198 (w), 1163
(w), 1164 (m), 1069 (m), 1027 (w), 995 (w), 841 (s), 749 (m), 738
(m), 697 (m), 595 (w), 558 (m), 502 (w), 475 (w) cm−1.
Synthesis of 8. Complex 8 was synthesized using the same
procedure described for 5. The crude product was purified by
chromatography on neutral Al2O3 using ethyl acetate/MeOH (20/1 v/
1
v) as eluent. Yield: 0.13 g (43.2% based on Ir). H NMR (500 MHz,
CD2Cl2): δ 8.71 (s, 1H), 8.61 (s, 1H), 8.30−8.34 (m, 2H), 8.15−8.23
(m, 3H), 8.04−8.06 (m, 2H), 7.34−7.51 (m, 17H), 7.00−7.06 (m,
2H), 6.78−6.82 (m, 2H), 6.28−6.30 (m, 2H), 5.36−5.37 (m, 2H),
5.15 (br, 1H), 4.37−4.61 (m, 4H), 3.16−3.21 (m, 1H), 2.57−2.95 (m,
10H), 1.93−2.37 (m, 8H), 1.75−1.78 (m, 2H), 1.13−1.69 (m, 25H),
0.90−0.95 (m, 11H) ppm. 13C{1H} NMR (125 MHz, CD2Cl2): δ
166.0−166.1 (m), 164.6 (d), 163.4−163.6 (m), 162.6 (d), 161.4−
161.5 (m), 155.4, 155.3, 153.3, 153.3, 152.8, 152.8, 147.5, 147.5, 147.3,
147.2, 129.8, 139.7, 137.6, 137.5, 130.6, 130.6, 130.2, 130.1, 128.4,
128.4, 128.3, 128.0, 128.0, 127.9, 127.6, 127.6, 127.0, 126.9, 126.1,
125.9, 125.4, 125.3, 125.1, 124.7, 124.5, 124.3, 117.3, 117.2, 99.4−99.9
(m), 72.3, 71.7, 61.5, 61.2, 50.8, 50.6, 50.0, 49.9, 37.5, 37.4, 31.9, 29.7,
29.4, 27.3, 27.2, 26.4, 26.3, 25.4, 25.3, 23.1, 23.0, 22.7, 13.9, 11.8, 11.7
ppm. 19F NMR (282 MHz, CD2Cl2): δ 3.49 (s), 0.96 (s), −30.41 to
−30.38 (m), −31.73 (d), −32.00 (d) ppm. MS (ESI; CH2Cl2, 180
°C): m/z 672.5 [Ir(L2)2(bipy) + H]2+; 1343.4 [Ir(L2)2(bipy)]+. Anal.
Calcd for C74H70F10IrN6O2P: C, 59.71; H, 4.74; N, 5.65. Found: C,
59.98; H, 5.00; N, 4.82. IR (KBr pellet): 2930 (s), 2860 (m), 1737
(w), 1599 (s), 1573 (m), 1544 (s), 1515 (w), 1448 (m), 1411 (m),
1361 (m), 1289 (w), 1254 (m), 1201 (w), 1162 (m), 1109 (s), 1065
(w), 1027 (w), 991 (s), 938 (w), 909 (w), 842 (s), 763 (w), 726 (m),
699 (m), 613 (w), 557 (m), 530 (w), 497 (w) cm−1.
ASSOCIATED CONTENT
■
S
* Supporting Information
1
Figures giving ESI mass, H NMR, and 13C NMR spectra for
L2′ and 3−10, 19F NMR for L2′, 3, 4, and 8−10, and 31P NMR
spectra for 7 and 10. This material is available free of charge via
the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: andyhor@nus.edu.sg (T.S.A.H.); david.young@ubd.
edu.bn (D.J.Y.).
Synthesis of 9. Complex 9 was synthesized using the same
procedure described for 5. The crude product was purified by
chromatography on neutral Al2O3 using ethyl acetate/MeOH (20/1 v/
ACKNOWLEDGMENTS
1
■
v) as eluent. Yield: 0.13 g (42.2%). H NMR (500 MHz, CD2Cl2): δ
This work was supported by the National University of
Singapore (NUS) (R143-000-323-112). D.J.Y. and A.L.T.
9.16−9.17 (m, 2H), 8.67−8.76 (m, 6H), 8.50−8.52 (m, 3H), 8.33−
8.34 (m, 2H), 8.11−8.15 (m, 2H), 7.88−7.94 (m, 9H), 7.77−7.80 (m,
558
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gratefully acknowledge funding from the Universiti Brunei
Darussalam.
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