Stepwise formation of iridium(III) complexes with monocyclometalating and dicyclometalating phosphorus chelates

Article abstract of DOI:10.1021/ic202090j

With the motivation of assembling cyclometalated complexes without nitrogen-containing heterocycle, we report here the design and systematic synthesis of a class of Ir(III) metal complexes functionalized with facially coordinated phosphite (or phosphonite) dicyclometalate tripod, together with a variety of phosphine, chelating diphosphine, or even monocyclometalate phosphite ancillaries. Thus, treatment of [IrCl₃(tht)₃] with stoichiometric amount of triphenylphosphite (or diphenyl phenylphosphonite), two equiv of PPh₃, and in presence of NaOAc as cyclometalation promoter, gives formation of respective tripodal dicyclometalating complexes [Ir(tpit)(PPh₃)₂Cl] (2a), [Ir(dppit)(PPh₃) ₂Cl] (2b), and [Ir(dppit)(PMe₂Ph)₂Cl] (2c) in high yields, where tpitH₂ = triphenylphosphite and dppitH₂ = diphenyl phenylphosphonite. The reaction sequence that afforded these complexes is established. Of particular interest is isolation of an intermediate [Ir(tpitH)(PPh₃)₂Cl₂] (1a) with monocyclometalated phosphite, together with the formation of [Ir(tpit)(tpitH)(PPh₃)] (3a) with all tripodal, bidentate, and monodentate phosphorus donors coexisting on the coordination sphere, upon treatment of 2a with a second equiv of triphenylphosphite. Spectroscopic studies were performed to explore the photophysical properties. For all titled Ir(III) complexes, virtually no emission can be observed in either solution at room temperature or 77 K CH₂Cl₂ matrix. Time-dependent DFT calculation indicates that the lowest energy triplet manifold involves substantial amount of metal centered ³MC dd contribution. Due to its repulsive potential energy surface (PES) that touches the PES of ground state, the ³MC dd state executes predominant nonradiative deactivation process.

Full text of DOI:10.1021/ic202090j

Article
pubs.acs.org/IC
Stepwise Formation of Iridium(III) Complexes with
Monocyclometalating and Dicyclometalating Phosphorus Chelates†
Cheng-Huei Lin,† Chih-Yuan Lin,† Jui-Yi Hung,† Yao-Yuan Chang,† Yun Chi,*,† Min-Wen Chung,‡
Yuh-Chia Chang,‡ Chun Liu,‡ Hsiao-An Pan,‡ Gene-Hsiang Lee,‡ and Pi-Tai Chou*,‡
†Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan
‡Department of Chemistry, National Taiwan University, Taipei 106, Taiwan
S
* Supporting Information
ABSTRACT: With the motivation of assembling cyclo-
metalated complexes without nitrogen-containing heterocycle,
we report here the design and systematic synthesis of a class of
Ir(III) metal complexes functionalized with facially coordi-
nated phosphite (or phosphonite) dicyclometalate tripod,
together with a variety of phosphine, chelating diphosphine, or
even monocyclometalate phosphite ancillaries. Thus, treat-
ment of [IrCl3(tht)3] with stoichiometric amount of triphenylphosphite (or diphenyl phenylphosphonite), two equiv of PPh3,
and in presence of NaOAc as cyclometalation promoter, gives formation of respective tripodal dicyclometalating complexes
[Ir(tpit)(PPh3)2Cl] (2a), [Ir(dppit)(PPh3)2Cl] (2b), and [Ir(dppit)(PMe2Ph)2Cl] (2c) in high yields, where tpitH2
=
triphenylphosphite and dppitH2 = diphenyl phenylphosphonite. The reaction sequence that afforded these complexes is
established. Of particular interest is isolation of an intermediate [Ir(tpitH)(PPh3)2Cl2] (1a) with monocyclometalated phosphite,
together with the formation of [Ir(tpit)(tpitH)(PPh3)] (3a) with all tripodal, bidentate, and monodentate phosphorus donors
coexisting on the coordination sphere, upon treatment of 2a with a second equiv of triphenylphosphite. Spectroscopic studies
were performed to explore the photophysical properties. For all titled Ir(III) complexes, virtually no emission can be observed in
either solution at room temperature or 77 K CH2Cl2 matrix. Time-dependent DFT calculation indicates that the lowest energy
triplet manifold involves substantial amount of metal centered 3MC dd contribution. Due to its repulsive potential energy surface
3
(PES) that touches the PES of ground state, the MC dd state executes predominant nonradiative deactivation process.
phine and its functionalized derivatives, selective formation of
five-membered metallacycles occurs at the benzyl site, hence it
is feasible to form stable five-membered metal−chelate bonding
(Scheme 1). In general, these C and P coordinated chelates also
1. INTRODUCTION
Bidentate ligands such as 2,2′-bipyridine or relevant diimine
chelate play an important role in the development of classical
coordination chemistry, catalytic reactions, and modern
material chemistry employing transition-metal based com-
pounds.1 However, 2,2′-bypyridine is a neutral chelate, so that it
solely relies on the nitrogen-to-metal dative bonding to stabilize
the resulting metal complexes. For the purpose of design and
synthesis of more robust metal complexes, it is preferable to
select cyclometalating chelates; thus, in addition to the
nitrogen−metal dative bonding, it allows formation of
carbon-to-metal covalent interaction and in turn provides the
necessary stability. As a result, 2-phenyl pyridine and its
functionalized analogues have been selected as the best ligands
for synthesizing cyclometalates complexes.2 Alternatively,
cyclometalation also widely occurred at a variety of complexes
involving late transition-metal elements.3 Indeed, the growth of
the cyclometalation compounds stimulates many studies aimed
at elucidation of the mechanistic pathway or at how to widen
the reaction scopes.4 Interested readers can consult the relevant
articles2−4 for the necessary information.
Scheme 1. Schematic Diagram for Benzyldiphenylphosphine
Cyclometalation
represent a class of “non-conjugated” ancillary chelates,6 for
which the cyclometalate aromatic entity and PPh2 group are
separated by a methylene group. Both fragments show stronger
ligand-field strength and are capable of destabilizing the metal-
centered dd excited states concurrently. As anticipated, after
incorporating additional chromophores with desired ligand-
centered ππ* energy gap, decent blue to true-blue phosphor-
Similar to the nitrogen-containing cyclometalate, the metal−
phosphine coordination also allows a suitable geometrical
arrangement that favors subsequent C−H activation at the
nearby aromatic pendant.5 In the case of benzyldiphenylphos-
Received: September 26, 2011
Published: January 24, 2012
© 2012 American Chemical Society
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Inorganic Chemistry
Article
7.35−7.32 (m, 14H), 7.19 (t, J = 6.5 Hz, 7H), 7.03 (t, J = 7.0 Hz,
12H), 6.97 (d, J = 8.5 Hz, 2H), 6.51 (t, J = 7.5 Hz, 2H), 6.42 (t, J = 7.5
Hz, 2H), 6.32 (d, J = 7.5 Hz, 2H). 31P−{1H} NMR (202 MHz, CDCl3,
294 K): δ 116.3 (t, J = 13.0 Hz, 1P), −8.8 (d, J = 13.0 Hz, 2P). Anal.
Calcd for C54H43ClIrO3P3: C, 59.12; H, 4.04. Found: C, 61.16; H,
4.09.
Synthesis of [Ir(dppit)(PPh3)2Cl] (2b). [IrCl3(tht)3] (200 mg,
0.36 mmol), diphenyl phenylphosphonite (dppitH2, 120 mg, 0.40
mmol), and PPh3 (200 mg, 0.76 mmol) were added to 10 mL of
degassed decalin and the mixture was heated to 180 °C for 12 h. After
cooling to RT, sodium acetate (100 mg, 1.22 mmol) was added and
the mixture was heated to 135 °C for another 4 h. After cooling to RT
and removal of solvent, the residue was purified by silica gel column
chromatography, eluting with 1:3 mixture of ethyl acetate and hexane.
The white crystals of 2b were obtained by slow diffusion of hexane
into CH2Cl2 solution at RT (130 mg, 0.12 mmol, 35%).
escent metal complexes can be realized via tailored synthetic
protocols.7
Another class of phosphorus donors is triphenylphosphite
P(OPh)3 and diphenyl phenylphosphonite PPh(OPh)2, for
which the phenoxy groups are capable of undergoing facile
cyclometalation and affording the respective M(P∧C2) tripodal
fragment. Bearing such expectation in mind, we then carry out
the reactions of Ir(III) metal reagent [IrCl3(tht)3] with a
mixture of phosphine and phosphite (or phosphonite). The
well controlled reaction stoichiometry is expected to induce
double cyclometalation on the phosphite (or phosphonite)
ligand and afford the anticipated tripodal P∧C2 chelating
arrangement. Thus, the resulting facial tripod is different from
that of the well-known pincer chelate of the types P^C^P and
Spectral Data of 2b. MS (FAB, 35Cl, 193Ir): m/z 1045 (M + 1)+.
1H NMR (500 MHz, CD2Cl2, 294 K): δ 7.64 (d, J = 5.5 Hz, 2H),
7.30−7.18 (m, 19H), 7.06−6.90 (m, 14H), 6.89 (td, J = 7.5, 3.5 Hz,
2H), 6.55 (t, J = 7.5 Hz, 2H), 6.45 (d, J = 7.5 Hz, 2H), 6.40 (t, J = 7.5
Hz, 2H). 31P−{1H} NMR (202 MHz, CD2Cl2, 294 K): δ 144.4 (t, J =
4.8 Hz, 1P), −9.8 (d, J = 4.8 Hz, 2P). Anal. Calcd for C54H43ClIrO2P3:
C, 62.09; H, 4.15. Found: C, 61.85; H, 4.43.
Synthesis of [Ir(dppit)(PMe2Ph)2Cl] (2c). [IrCl3(tht)3] (150 mg,
0.27 mmol), dppitH2 (87 mg, 0.29 mmol), PMe2Ph (81 mg, 0.59
mmol), and sodium acetate (110 mg, 1.35 mmol) were combined in
degassed decalin (10 mL) and the mixture was heated to 180 °C for 30
h. After cooling to RT and removal of solvent, the residue was purified
by silica gel column chromatography, eluting with a 1:3 mixture of
ethyl acetate and hexane. The white crystals of 2c were obtained by
slow diffusion of hexane into a CH2Cl2 solution at RT (121 mg, 0.15
mmol, 57%).
P^N^P, for which only the meridional bonding mode is
reported.8
2. EXPERIMENTAL SECTION
General Procedures. All reactions were performed under argon
atmosphere and solvents were distilled from appropriate drying agents
prior to use. Commercially available reagents were used without
further purification unless otherwise stated. All reactions were
monitored using precoated TLC plates (0.20-mm with fluorescent
indicator UV254). Mass spectra were obtained on a JEOL SX-102A
instrument operating in electron impact (EI) or fast atom bombard-
1
Spectral Data of 2c. MS (FAB, 35Cl, 193Ir): m/z 796 (M)+. H
NMR (500 MHz, CD2Cl2, 294 K): δ 8.03 (dd, J = 7.0, 3.0 Hz, 2H),
7.52 (td, J = 7.0, 1.0 Hz, 1H), 7.32 (t, J = 7.5 Hz, 2H), 7.25 (td, J = 8.0,
3.5 Hz, 2H), 7.16 (t, J = 7.0 Hz, 4H), 6.99 (dd, J = 12.0, 7.5 Hz, 2H),
6.93−6.91 (m, 4H), 6.88−6.84 (m, 2H), 6.79 (t, J = 8.0 Hz, 4H), 1.42
(d, J = 8.5 Hz, 6H), 1.10 (d, J = 9.0 Hz, 6H). 31P−{1H} NMR (202
MHz, CD2Cl2, 294 K): δ 141.3 (t, J = 4.8 Hz, 1P), −42.6 (d, J = 4.8
Hz, 2P). Anal. Calcd for C34H35ClIrO2P3: C, 51.29; H, 4.43. Found: C,
51.08; H, 4.54.
1
ment (FAB) mode. H and 13C NMR spectra were recorded on a
Varian Mercury-400 or an INOVA-500 instrument. Elemental analysis
was carried out with a Heraeus CHN-O Rapid Elementary Analyzer.
Diphenyl phenylphosphonite (dppitH2)9 and [IrCl3(tht)3]10 were
synthesized using methods reported in the literature.
Synthesis of [Ir(tpitH)(PPh3)2Cl2] (1a). [IrCl3(tht)3] (110 mg,
0.20 mmol), triphenylphosphite (tpitH2, 70 mg, 0.22 mmol), and
triphenyl phosphine (PPh3, 115 mg, 0.44 mmol) were added into 10
mL of decalin and the mixture was heated to 180 °C for 12 h. After
cooling to RT, the solution was concentrated and mixed with excess of
hexane to induce precipitation. The white crystals of 1a were obtained
by slow diffusion of hexane into a CH2Cl2 solution at RT (153 mg,
0.14 mmol, 70%).
Synthesis of [Ir(tpit)(tpitH)(PPh3)] (3a). Complex 2a (69 mg,
0.07 mmol), triphenylphosphite (22 mg, 0.07 mmol), and sodium
acetate (12 mg, 0.15 mmol) were added to 10 mL of decalin and the
mixture was heated to 120 °C for 6 h. After cooling to RT and removal
of solvent, the residue was purified by silica gel column
chromatography, eluting with a 4:1 mixture of dichloromethane and
hexane. The white crystals of 3a were obtained by slow diffusion of
hexane into CH2Cl2 solution at RT (54 mg, 0.05 mmol, 77%).
1
Spectral Data of 3a. MS (FAB, 193Ir): m/z 1072 (M)+. H NMR
Spectral Data of 1a. MS (FAB, 35Cl, 193Ir): m/z 1061 (M − Cl)+.
1H NMR (400 MHz, CDCl3, 294 K): δ 7.60−7.64 (m, 12H), 7.10 (t, J
= 7.4 Hz, 6H), 7.00 (t, J = 7.6 Hz, 12H), 6.94−6.84 (m, 6H), 6.71 (d, J
= 8.0 Hz, 1H), 6.64 (t, J = 7.4 Hz, 1H), 6.53 (d, J = 8.0 Hz, 4H), 6.49
(d, J = 8.0 Hz, 1H), 6.02 (t, J = 7.4 Hz, 1H). 31P−{1H} NMR (202
MHz, CDCl3, 294 K): δ 76.6 (t, J = 22.5 Hz, 1P), −12.8 (d, J = 22.5
Hz, 2P). Anal. Calcd for C54H44Cl2IrO3P3: C, 59.12; H, 4.04. Found:
C, 58.43; H, 3.89.
(500 MHz, CD2Cl2, 294 K): δ 7.48 (t, J = 8.0 Hz, 1H), 7.35 (t, J = 8.0
Hz, 2H), 7.26−7.20 (m, 5H), 7.19−7.15 (m, 4H), 7.11 (dd, J = 8.0,
3.0 Hz, 1H), 7.06−7.04 (m, 15H), 6.97 (d, J = 8.5 Hz, 2H), 6.77−6.73
(m, 4H), 6.70 (t, J = 7.5 Hz, 1H), 6.60−6.55 (m, 5H), 6.51 (t, J = 7.5
Hz, 1H), 6.21 (dd, J = 8.0, 3.0 Hz, 1H). 31P−{1H} NMR (202 MHz,
CD2Cl2, 294 K): δ 141.8 (dd, J = 20.0, 12.1 Hz, 1P), 114.5 (dd, J =
20.0, 12.1 Hz, 1P), −4.1 (t, J = 20.0 Hz, 1P). Anal. Calcd for
C54H42IrO6P3: C, 60.50; H, 3.95. Found: C, 60.33; H, 4.02.
Synthesis of [Ir(tpit)(PPh3)2Cl] (2a). [IrCl3(tht)3] (110 mg, 0.20
mmol), triphenylphosphite (70 mg, 0.22 mmol), and PPh3 (115 mg,
0.44 mmol) were added into 10 mL of decalin and the mixture was
heated to 180 °C for 12 h. After cooling to RT, sodium acetate (80
mg, 1.00 mmol) was added and the mixture was heated to 135 °C for
another 4 h. After cooling to RT and removal of solvent, the residue
was purified by silica gel column chromatography, eluting with 1:3
mixture of ethyl acetate and hexane. The white crystals of 2a were
obtained by slow diffusion of hexane into CH2Cl2 solution at RT (138
mg, 0.13 mmol, 65%).
Synthesis of [Ir(tpit)(dppb)Cl] (4a). Complex 2a (100 mg, 0.10
mmol) and 1,2-bis(diphenylphosphino)benzene (dppb, 47 mg, 0.11
mmol) were added to 10 mL of decalin and the mixture was heated to
110 °C for 2 h. After cooling to RT and removal of solvent, the residue
was purified by silica gel column chromatography, eluting with a 4:1
mixture of dichloromethane and hexane. The white crystals of 4a were
obtained by slow diffusion of hexane into CH2Cl2 solution at RT (77
mg, 0.08 mmol, 83%).
Spectral Data of 4a. MS (FAB, 35Cl, 193Ir): m/z 983 (M + 1)+. 1H
NMR (400 MHz, CDCl3, 294 K): δ 7.65−7.54 (m, 10H), 7.37−7.29
(m, 2H), 7.28−7.20 (m, 4H), 7.18−7.09 (m, 8H), 7.08−6.95 (m, 5H),
6.84−6.75 (m, 4H), 6.65 (t, J = 8.0 Hz, 2H), 6.33 (d, J = 8.0 Hz, 2H).
Spectral Data of 2a. MS (FAB, 35Cl, 193Ir): m/z 1061 (M + 1)+.
1H NMR (500 MHz, CDCl3, 294 K): δ 7.63 (dd, J = 7.0, 2.5 Hz, 2H),
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Inorganic Chemistry
Article
Table 1. Crystal Data and Refinement Parameters for Complexes 1a, 2a, 2c, 3a, 4b, and 5b
1a
2a
2c
3a
4b
5b
empirical formula
formula weight
temperature, K
crystal system
space group
a, Å
C44H36.80Cl3.20Ir0.80O2.40P2.40 C55H45Cl3IrO3P3
C34H35ClIrO2P3
796.18
C54H42IrO6P3
1071.99
C49H39Cl3IrO2P3
1051.26
C49H37IrNO2P3S
988.97
945.46
1145.37
150(2)
150(2)
150(2)
150(2)
150(2)
150(2)
monoclinic
P21/c
triclinic
P1
monoclinic
P21/n
triclinic
monoclinic
P21/n
orthorhombic
Pbca
P1
13.0584(6)
12.6063(6)
31.5539(16)
11.7548(5)
13.1516(6)
16.9951(8)
85.774(1)
70.345(1)
69.699(1)
2317.82(18)
2
9.8586(6)
19.3800(11)
16.0905(9)
11.8016(2)
12.3056(3)
16.2714(4)
81.0150(9)
82.7381(12)
70.8637(9)
2197.88(8)
2
10.9011(7)
22.1877(14)
17.7327(11)
20.2319(10)
19.0994(9)
20.9480(11)
b, Å
c, Å
α, °
β, °
γ, °
volume, Å3
99.463(1)
94.5344(12)
91.5227(13)
5123.7(4)
5
3064.6(3)
4
4287.5(5)
4
8094.7(7)
8
Z
ρcalcd, Mg m−3
1.532
2.951
1.641
1.726
4.632
1.620
1.629
3.453
1.623
3.512
absorption
3.203
3.201
coefficient, mm−1
F(000)
2360
1144
1576
1072
2088
3936
crystal size, mm3
0.43 × 0.20 × 0.20
35231
0.27 × 0.25 × 0.15 0.25 × 0.20 × 0.15 0.18 × 0.14 × 0.13 0.27 × 0.18 × 0.10 0.36 × 0.18 × 0.10
23947
reflections collected
23464
38394
32679
60149
independent
reflections
11737 [R(int) = 0.0377]
10588 [R(int) =
0.0311]
7038 [R(int) =
0.0298]
10067 [R(int) =
0.0554]
9834 [R(int) =
0.0341]
9301 [R(int) =
0.0559]
max., min
0.5898, 0.3635
11737/5/587
1.095
0.6451, 0.4784
10588/0/586
1.072
0.5434, 0.3906
7038/0/374
1.124
0.639, 0.579
10067/0/577
1.020
0.7239, 0.4557
9834/0/523
1.088
0.7203, 0.3646
9301/1/514
1.025
transmission
data/restraints/
parameters
goodness-of-fit on F2
final R indices [I >
2σ(I)]
R1 = 0.0404, wR2 = 0.1056 R1 = 0.0299, wR2 = R1 = 0.0255, wR2 = R1 = 0.0326, wR2
0.0692 0.0538 =0.0648
R1 = 0.0285, wR2 = R1 = 0.0261, wR2 =
0.0626 0.0584
R indices (all data)
R1 = 0.0501, wR2 = 0.1122 R1 = 0.0341, wR2 = R1 = 0.0279, wR2 = R1 = 0.0489, wR2 = R1 = 0.0331, wR2 = R1 = 0.0355, wR2 =
0.0767
0.0547
0.0746
0.0644
0.0632
largest different peak
and hole
1.862 and −1.046 e.Å−3
1.369 and −0.815
1.186 and −0.736
1.209 and −1.677
1.220 and −0.889
1.254 and −1.148
−3
−3
e.Å−3
e.Å−3
e.Å−3
e.Å
e.Å
1
Spectral Data of 5b. MS (FAB, 193Ir): m/z 990 (M + 1)+. H
NMR (400 MHz, CDCl3, 294 K): δ 7.77−7.74 (m, 2H), 7.69−7.67
(m, 2H), 7.39−7.30 (m, 6H), 7.15−7.09 (m, 8H), 7.07−7.00(m, 5H),
6.93−6.86 (m, 8H), 6.63−6.58 (m, 4H), 6.12 (d, J = 8.0 Hz, 1H), 6.09
(d, J = 8.0 Hz, 1H). 31P−{1H} NMR (202 MHz, CDCl3, 294 K): δ
146.0 (br, 1P), 17.3 (d, J = 3.8 Hz, 2P). Anal. Calcd for
C49H37IrNO2P3S: C, 59.51; H, 3.77; N, 1.42. Found: C, 59.45; H,
3.99; N, 1.81.
31P−{1H} NMR (202 MHz, CDCl3, 294 K): δ 117.3 (t, J = 9.9 Hz,
1P), 16.0 (d, J = 9.9 Hz, 2P). Anal. Calcd for C48H37ClIrO3P3: C,
58.68; H, 3.80. Found: C, 58.54; H, 4.05.
Synthesis of [Ir(dppit)(dppb)Cl] (4b). Complex 4b was prepared
from 2b using a procedure similar to that for 4a; yield: 95%.
Spectral Data of 4b. MS (FAB, 35Cl, 193Ir): m/z 967 (M + 1)+.
1H NMR (400 MHz, CDCl3, 294 K): δ 7.83−7.77 (m, 2H), 7.72−7.65
(m, 2H), 7.42 (t, J = 8.0 Hz, 2H), 7.35−7.23 (m, 7H), 7.15 (t, J = 8.0
Hz, 4H), 7.01−6.89 (m, 12H), 6.82 (t, J = 8.0 Hz, 2H), 6.59−6.50 (m,
4H), 6.25 (d, J = 8.0, 1H), 6.22 (d, J = 8.0, 1H). 31P−{1H} NMR (202
MHz, CDCl3, 294 K): δ 149.9 (t, J = 2.6 Hz, 1P), 16.6 (d, J = 2.6 Hz,
2P). Anal. Calcd for C48H37ClIrO2P3: C, 59.66; H, 3.86. Found: C,
58.70; H, 4.22.
Synthesis of [Ir(dppit)(PMe2Ph)2(NCS)] (6c). Complex 6c was
prepared from 2b using a procedure similar to that for 5a; yield: 64%.
Spectral Data of 6c. MS (FAB, 193Ir): m/z 820 (M + 1). 1H NMR
(400 MHz, CD3Cl, 294 K): δ 7.75−7.70 (m, 2H), 7.57 (t, J = 8.0 Hz,
1H), 7.36−7.30 (m, 4H), 7.18−7.14 (m, 6H), 6.93−6.88 (m, 6H),
6.76 (t, J = 8.0 Hz, 4H), 1.42 (d, J = 8.0 Hz, 6H), 1.13 (d, J = 8.0 Hz,
6H). 31P−{1H} NMR (202 MHz, CDCl3, 294 K): δ 139.7 (br, 1P),
−39.8 (d, J = 7.5 Hz, 2P). Anal. Calcd for C35H35IrNO2P3S: C, 51.34;
H, 4.31; N, 1.71. Found: C, 51.02; H, 4.65; N, 1.80.
Single Crystal X-ray Diffraction Studies. Single crystal X-ray
diffraction data were measured on a Bruker SMART Apex CCD
diffractometer using (Mo Kα) radiation (λ = 0.71073 Å). The data
collection was executed using the SMART program. Cell refinement
and data reduction were performed with the SAINT program. The
structure was determined using the SHELXTL/PC program and
refined using full-matrix least-squares. All crystallographic data and
refinement parameters are summarized in Table 1.
Photophysical Investigation and Theoretical Methodology.
Steady-state absorption, emission, and phosphorescence lifetime
measurements in solution and solid state have been described in our
previous reports.11 Calculations on electronic singlet and triplet states
of all titled complexes were carried out using the density functional
theory (DFT) with B3LYP hybrid functional.12 Restricted and
unrestricted formalisms were adopted in the singlet and triplet
Synthesis of [Ir(tpit)(dppb)(NCS)] (5a). Complex 4a (50 mg,
0.05 mmol) and potassium thiocyanate (50 mg, 0.51 mmol) were
added in 10 mL of DMF (10 mL) and the mixture was refluxed for 36
h. After cooling to RT and removal of solvent, the residue was purified
by silica gel column chromatography, eluting with a 4:1 mixture of
dichloromethane and hexane. The white crystals of 5a were obtained
by slow diffusion of hexane into CH2Cl2 solution at RT (36 mg, 0.04
mmol, 70%).
1
Spectral data of 5a. MS (FAB, 193Ir): m/z 1005 (M)+. H NMR
(400 MHz, CDCl3, 294 K): δ 7.67−7.63 (m, 4H), 7.46−7.33 (m,
12H), 7.29−7.25 (m, 2H), 7.19−7.12 (m, 6H), 7.07 (t, J = 6.0 Hz,
1H), 6.97 (t, J = 8.0 Hz, 4H), 6.82 (t, J = 6.0 Hz, 2H), 6.71 (t, J = 6.0
Hz, 2H), 6.63 (d, J = 8.0 Hz, 2H), 6.31 (d, J = 8.0 Hz, 2H). 31P−{1H}
NMR (202 MHz, CDCl3, 294 K): δ 117.3 (br, 1P), 17.22 (d, J = 14.9
Hz, 2P). Anal. Calcd for C49H37IrNO3P3S: C, 58.56; H, 3.71; N, 1.39.
Found: C, 58.41; H, 3.98; N, 1.41.
Synthesis of [Ir(dppit)(dppb)(NCS)] (5b). Complex 5b was
prepared from 4b using a procedure similar to that for 5a; yield: 85%.
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geometry optimization, respectively. A ″double-ζ″ quality basis set
consisting of Hay and Wadt’s effective core potentials (LANL2DZ)13
was employed for the Ir(III) metal atom, and a 6-31G* basis set14 was
employed for the rest of the atoms. The relativistic effective core
potential (ECP) replaced the inner core electrons of Ir(III) metal
atom, leaving only the outer core valence electrons (5s25p65d6) to be
concerned. Time-dependent DFT (TDDFT) calculations using the
B3LYP functional were then performed based on the optimized
structures at the ground state.15 Moreover, considering the solvation
effect, the calculations were then combined with an integral equation
formalism-polarizable continuum model (in dichloromethane), IEF-
PCM,16 implemented in Gaussian 03. Typically, 10 lower triplet and
singlet roots of the nonhermitian eigenvalue equations were obtained
to determine the vertical excitation energies. Oscillator strengths were
then deduced from the dipole transition matrix elements (for singlet
states only). All calculations were carried out using Gaussian 03.17
tBu2) and Ir(I) reagents [{Ir(μ-OMe)(cod)}2] or [Ir(cod)-
(py)2][PF6], for which the steric effect is proposed to be the
main driving force for the observed double cyclometalation.20
The dicyclometalation may be favored over monocyclometala-
tion as a means to minimize the intramolecular interaction
between the t-Bu groups in the phosphite ligand. However,
such a steric demand imposed by the bulky tBu groups does not
exist in our Ir(III) system. To gain more insight into the
phosphite cyclometalation, we thus carry out further inves-
tigation by conducting the reaction in presence of excess
triphenylphosphine to slow down the reaction sequence, so that
certain intermediate species can be isolated.
We first allowed [IrCl3(tht)3] to react with stoichiometric
amount of P(OPh)3 (also denoted as tpitH2) plus two equiv of
PPh3, but in absence of NaOAc. The addition of PPh3 or other
phosphorus donor is intended to prevent the formation of any
vacant coordination site that would yield the chloride-bridged
dimer, which is prevalent for the chloride containing Ir(III)
metal complexes;21 otherwise, severe decomposition could take
place. As indicated in Scheme 3, this reaction in presence of
3. RESULTS AND DISCUSSION
Stepwise Dicyclometalation. It was reported that treat-
ment of [IrCl3(tht)3] (tht = tetrahydrothiophene) with an
equimolar amount of triphenylphosphite (tpitH2) and diimine,
such as 2,2′-bipyridine and 2,2′-biquinoline, gave formation of
novel diimine complexes A and B (see below) in high yields.18
The added diimine and phosphite would easily replace all three
tht ligands and then formed certain unknown intermediate
initially. Moreover, the phosphite coordination would also
bring two of its phenyl substituents near the central Ir(III)
atom and then facilitate the subsequent double cyclometalation
with the assistance of sodium acetate added to the mixture.
This strategy presents a synthetic protocol in obtaining a new
class of emissive Ir(III) complexes without the employment of
traditional nitrogen-containing polyaromatic cyclometalates.
Scheme 3. Synthetic Route to the Ir(III) Complexes 1a and
2a (Reagents and Conditions: (i) 180 °C, decalin, 12 h, (ii)
NaOAc, 135 °C, 4 h)
PPh3 afforded one major Ir(III) product [Ir(tpitH)(PPh3)2Cl2]
(1a) which can be isolated via simple precipitation, followed by
crystallization. The 31P−{1H} NMR spectrum shows two
signals at δ 76.57 and 12.78 with intensity ratio of 1:2, showing
the attachment of one phosphite and two phosphines,
respectively.
The single-crystal X-ray structures of 1a were then
determined. Figure 1 shows the ORTEP drawing, along with
Upon replacing the diimine with two equal molar ratio of
PPh3, the same reaction of [IrCl3(tht)3] with triphenylphos-
phite and excess of sodium acetate in refluxing decalin solution
resulted in a high yield conversion to a dicyclometalated
phosphite complex [Ir(tpit)(PPh3)(OAc)] (C) (c.f. Scheme
Scheme 2. Synthetic Route to the Ir(III) Complexes C and D
(Reagents and Conditions: (i) 190 °C, decalin, 6 h, (ii)
(bptz)H, 190 °C, 12 h)
Figure 1. ORTEP diagram of 1a with ellipsoids shown at 30%
probability level. Selected bond distances: Ir−P(1) = 2.1898(12), Ir−
P(3) = 2.3956(12), Ir−P(2) = 2.3968(12), Ir−C(1) = 2.079(5), Ir−
Cl(2) = 2.4189(11), and Ir−Cl(1) = 2.4541(11) Å.
2).19 Subsequent replacement of acetate in C with 3-tert-butyl-
5-(2-pyridyl) triazolate chromophoric chelate gave isolation of
the blue-emitting phosphor [Ir(tpit)(PPh3)(bptz)] (D) in high
yield (∼ 60%). Intriguingly, the complexes with relevant P^C2
tripodal chelate were known as products from reaction of the
hindered phosphites P(OAr)3 (Ar = C6H4-2-tBu or C6H3-2,4-
selected bond lengths and angles that are given in the caption.
The structure is in agreement with the NMR data; in particular
it is clear that the phosphite has underwent only mono-
cyclometalation, giving a symmetrical core arrangement with
two PPh3 and two chloride ligands occupying trans and cis
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coordination sites. Furthermore, the metal−phosphite distance
(Ir−P(1) = 2.1898(12) Å) is substantially shorter than that of
metal−phosphine distances (Ir−P(3) = 2.3956(12) and Ir−
P(2) = 2.3968(12) Å). This reflects the weaker Ir−P bonding
for PPh3, a result of greater steric demand, plus weaker π-
accepting character of its phosphorus atom. Furthermore, both
Ir−Cl distances are identical within the experimental error,
despite the fact that they are located in quite different
environments, i.e., located trans to the cyclometalated carbon
and phosphorus atoms, respectively.
In an attempt to study the accompanied reactivity pattern, 1a
was then heated in decalin and in presence of NaOAc at 135 °C
for 4 h. The subsequent major product [Ir(tpit)(PPh3)2Cl]
(2a) showed no obvious difference in color from its starting
material 1a, whereas its chemical stability had been significantly
improved, as revealed by showing no visible decomposition
during separation employing silica gel column chromatography.
Next, the FAB analysis showed a molecular ion (M+) at m/z
1060 which is 36 units smaller that that of 1a, confirming the
elimination of an additional HCl fragment. In good agreement
with the FAB data, the 31P−{1H} spectrum recorded shows the
presence of two mutually coupled multiplets at δ 116.26 and δ
−8.75 (J = 13.0 Hz) with intensity ratio 1:2. Therefore, 2a is
assigned to possess the double cyclometalated structure as
shown in Scheme 3. Moreover, the conversion from 1a to 2a
required only higher reaction temperature, extended reaction
time, and addition of sodium acetate (NaOAc) as the
cyclometalation promoter. Direct synthesis of 2a can then be
done employing a one-pot sequence starting from [IrCl3(tht)3]
and a mixture of PPh3, phosphate P(OPh)3, and NaOAc.
Moreover, switching from phosphite P(OPh)3 to phosphonite
PPh(OPh)2 and replacing PPh3 with PMe2Ph gave isolation of
two more functionalized derivatives 2b and 2c, both in
excellent yields (Scheme 4). This expanded reaction scope
Figure 2. ORTEP diagram of 2a with ellipsoids shown at 30%
probability level. Selected bond distances: Ir−P(1) = 2.1529(8), Ir−
P(3) = 2.4433(8), Ir−P(2) = 2.4528(9), Ir−C(7) = 2.081(3), Ir−C(1)
= 2.103(3), and Ir−Cl(1) = 2.4385(8) Å; bond angle: P(2)−Ir-P(3) =
104.97(3)°.
Scheme 4. Synthetic Route to the Ir(III) Complexes 2b and
2c (Reagents and Conditions: (i) 180 °C, decalin, 12 h)
Figure 3. ORTEP diagram of 2c with ellipsoids shown at 30%
probability level. Selected bond distances: Ir−P(1) = 2.1896(8), Ir−
P(2) = 2.3698(8), Ir−P(3) = 2.3812(8), Ir−Cl(1) = 2.4469(7), Ir−
C(1) = 2.090(3), and Ir−C(7) = 2.104(3) Å; bond angle: P(2)−Ir−
P(3) = 100.28(3)°.
of the respective PPh3 ligands. This variation of Ir−P distances
seems to be parallel to the general electronic and steric
properties of phosphorus donor ligands.23
Additional Cyclometalation Reaction. When complex
2a was treated with 1 equiv of P(OPh)3 in presence of NaOAc,
a new complex [Ir(tpit)(tpitH)(PPh3)] (3a) was formed after
heating at 120 °C for 6 h. The 31P−{1H} NMR spectrum of 3a
exhibits three signals at δ 141.84, 114.52, and −4.11. Based on
their 31P NMR chemical shift data, we concluded the existence
of two phosphites and one PPh3 on the Ir(III) coordination
sphere, i.e., showing the occurrence of phosphine−phosphite
exchange. Further evidence is provided by the single crystal X-
ray analysis shown in Figure 4. As can be seen, the Ir(III) center
adopts a distorted octahedral coordination geometry, which is
then coordinated by one dicyclometalated and one mono-
cyclometalated phosphite, together with one remaining PPh3.
Remarkably, all three cyclometalated phenyl groups and
phosphorus donor atoms are now adopting the facial mode,
which has been considered to be the thermodynamically
favorable coordination motif for a majority of Ir(III) metal
complexes.24
then confirms the sequential mono- and dicyclometalation
capability on the Ir(III) metal center, for both phosphite and
phosphonite ligands demonstrated earlier.
Crystals of complexes 2a and 2c were grown by slow
diffusion of hexane into the CH2Cl2 solution. The X-ray crystal
structural data are in line with the spectral data just discussed,
with selected bond distances and angles given in the captions of
Figures 2 and 3. Their structural feature is akin to three Ir(III)
complexes with facially coordinated phosphite tripod, namely
hydride complexes [IrH(cod){P(OC6H4)2(OC6H5)}] and
[IrH{P(OC6H2-2,4-tBu2)2(OC6H3-2,4-tBu2)}(cod)] reported
by Bedford,20 and γ-picoline coordinated derivative [IrP-
{(OC6H3Me)2(OC6H4Me)}Cl(4Me-py)2] reported by Single-
ton.22 Moreover, close comparison between 2a and 2c shows
that the phosphite Ir−P distance (2.1529(8) Å) is notably
shorter than the phosphonite Ir−P distance (2.1896(8) Å),
while the PMe2Ph also shows stronger Ir−P bonding than that
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Scheme 6. Synthetic Route to the Ir(III) Complexes 4b, 5b,
and 6c (Reagents and Conditions: (i) o-C6H4(PPh2)2, 110
°C, 2 h, (ii) KNCS, DMF, reflux, 24 h)
Figure 4. ORTEP diagram of 3a with ellipsoids shown at 30%
probability level. Selected bond distances: Ir−P(1) = 2.2340(9), Ir−
P(2) = 2.2518(9), Ir−P(3) = 2.3940(10) Å, Ir−C(6) = 2.133(3), Ir−
C(12) = 2.118(4), and Ir−C(24) = 2.126(3) Å.
increased bond strength. In contrast, the chloride−thiocyanate
exchange reaction, which gives [Ir(tpit)(dppb)(NCS)] (5a)
and [Ir(dppit)(dppb)(NCS)] (5b), proceeds with better yields
than that afforded the counterpart [Ir(dppit)-
(PMe2Ph)2(NCS)] (6c), despite the fact that all of them
need higher reaction temperature and extended reaction time.
Evidently, the low yield in 6c is attributed to the inferior
stability of its starting material 2c, which possesses two
monodentate PMe2Ph instead of the more robust chelating
dppb existing in both 4a and 4b.
Simple Ligand Substitution. Parallel to the phosphine-to-
phosphite exchange that led to the cyclometalation of
phosphite, replacement of PPh3 in both 2a and 2b with 1,2-
bis(diphenylphosphino)benzene (dppb) afforded the simple
substitution products [Ir(tpit)(dppb)Cl] (4a) and [Ir(dppit)-
(dppb)Cl] (4b) in good yields (Schemes 5 and 6). The greater
Scheme 5. Synthetic Route to the Ir(III) Complexes 3a−5a
(Reagents and Conditions: (i) P(OPh)3, NaOAc, 120 °C,
decalin, 6 h, (ii) o-C6H4(PPh2)2, 110 °C, 2 h, (iii) KNCS,
DGME, 190 °C)
For confirming the bonding mode of dppb chelate, the
molecular structures of both Ir(III) complexes 4b and 5b were
determined by X-ray crystallographic analyses. Figures 5 and 6
rigidity of the chelating dppb may enhance its stability against
further phosphine substitution. We then made attempts to
replace chloride with either phenyl or phenylacetylide fragment.
These reactions were attempted by treatment of 4a (or 4b)
with phenylmagnesium bromide in anhydrous dimethoxy-
ethane or with phenylacetylene in triethylamine and in
presence of CuI as catalyst. These two procedures are known
to be useful for incorporation of the respective organic group
into the late transition metal halide complexes;25 however,
none of them can yield the anticipated products in the current
Ir(III) system. The poor reactivity could be attributed to the 3+
oxidation state of the Ir(III) atoms, which could enhance the
covalent character of the Ir−Cl bonding and hence the
Figure 5. ORTEP diagram of 4b with ellipsoids shown at 30%
probability level. Selected bond distances: Ir−P(1) = 2.2084(8), Ir−
P(2) = 2.3544(7), Ir−P(3) = 2.3478(8), Ir−Cl(1) = 2.4211(7), Ir−
C(1) = 2.101(3), and Ir−C(7) = 2.108(3) Å; bond angle: P(2)−Ir−
P(3) = 84.69(3)°.
show the ORTEP drawings of 4b and 5b with selected bond
distances and angles provided in the captions. It is notable that
the coordination environments around the Ir(III) metal center
of 4b and 5b are essentially the same, and each iridium atom
possesses an octahedral geometry. The bite angles of dppb for
4b and 5b are P(2)−Ir−P(3) = 84.69(3) and 84.68(3)°,
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Figure 8. Absorption spectra of 2b−6c in CH2Cl2 solution at room
Figure 6. ORTEP diagram of 5b with ellipsoids shown at 30%
probability level. Selected bond distances: Ir−P(1) = 2.2062(7), Ir−
P(2) = 2.3508(7), Ir−P(3) = 2.3611(7), Ir−N(1) = 2.072(2), Ir−
C(1) = 2.113(3), and Ir−C(7) = 2.099(3) Å; bond angle: P(2)−Ir−
P(3) = 84.68(3)°.
temperature (symbols as given in key).
metal-centered (MC) dd transition (vide infra) in the singlet
manifold. The lower lying states all located in the UV region (<
400 nm) are predictable mainly due to the lack of π-extended,
highly conjugated ligands for the titled complexes. As for the
luminescence property, all titled complexes are nonemissive in
degassed CH2Cl2 solution as well as in solid state at RT. Also,
barely any emission could be resolved in the 77 K CH2Cl2
matrix. The lack of emission may not be unexpected, which can
be attributed to the high ππ* energy gap for the nonconjugated
phenyl fragments associated with the Ir(III) metal atom. Such a
design strategy reduces π-conjugation length significantly and
thus tunes the absorption band to the UV region, at which the
absorption is plausibly coupled to the MC dd transition that is
then subject to dominant quenching via interaction between
MC dd repulsive potential energy surface (PES) and PES of the
ground state.27
respectively, for which both are close to the ideal bite angle for
undistorted octahedral metal complexes, and are much more
acute than that of the P−Ir−P angle observed for 2a and 2c
(c.f. 104.97(3) and 100.28(3)°), confirming the thermodynam-
ical consequence of dual phosphine-to-chelating diphosphine
substitution. Finally, structure of 5b also reveals an N-
coordination of thiocyanate, which is consistent with the
bonding mode observed for other thiocyanate-containing metal
complexes.26
Photophysical Properties. Figures 7 and 8 display the
absorption spectra of all titled Ir(III) complexes 2a−6c
To gain more in-depth information into the photophysical
properties, time-dependent (TD) DFT was then performed via
the use of functional B3LYP and the 6-31G(d)/LANL2DZ
basis set. Also, the PCM model in CH2Cl2 is incorporated to
take the solvation effect into account (see Experimental Section
for detail). Figures 9 and 10 depict the selected frontier orbitals
involved in lower-lying transitions of all titled complexes. The
calculated energy gaps and corresponding assignments of each
transition are listed in Table 2. Accordingly, the calculated S0 →
S1 transition (in terms of wavelength) of all studied complexes
is close to the observed onsets of the lowest energy absorption
spectra depicted in Figures 7 and 8. Taking 2a and 2b as
examples, the computational energy gaps of the S1 states (2a:
337 nm, 2b: 362.3 nm) are qualitatively in agreement with the
onset of their lowest energy absorption peak. This result
indicates that the TDDFT calculation works well in predicting
the lowest Franck−Condon excited state for absorption based
on the S0 optimized geometries of all Ir(III) metal complexes.
Table 2 also lists the T1 energy gap and the frontier orbitals
involved in the S0−T1 transition, both of which play a key role
in interpreting the lack of emission under all conditions. As for
the transition characteristic, frontier orbital analyses indicate
that the lowest energy triplet states (T1) for all Ir(III)
complexes are primarily attributed to HOMO → LUMO
transition (c.f. Table 2), mixed with transitions from lower lying
HOMO-n to higher lying LUMO+m orbitals. Careful
examination indicates that the T1 state, to certain extents,
always involves non-negligible amount of dσ* contribution (c.f.
Figure 7. Absorption spectra of 2a−5a in CH2Cl2 solution at room
temperature (symbols as given in key).
recorded in degassed CH2Cl2 at room temperature. In general,
all complexes exhibit allowed absorption bands in the UV
region of <275 nm, for which ε values at the peak maxima are
measured to be >1.5 × 104 M−1 cm−1 and can thus be attributed
to ligand-centered ππ* transition. The broad band at longer
wavelength up to 330 nm, as revealed by their relatively lower
extinction coefficients (<1.0 × 103 M−1 cm−1), is assigned to the
tail of ππ* transition overlapping with the metal-to-ligand
charge transfer (MLCT) transition and a certain extent of
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Figure 9. Selected frontier orbitals involved in the lower-lying transition for 2a−5a.
3
2a−c, 3a, and 6c), except for those involving the dppb chelate
(c.f. 4a−b and 5a−b), where LUMO is mainly localized on the
dppb π* orbital, due to the lower gap of o-phenylene fragment
versus that of phenyl groups of triphenylphosphite. Never-
theless, other higher lying orbitals such as LUMO+1 to LUMO
+3, which are also involved in the T1 state, still have substantial
contribution from the dσ* orbital. Evidently, all Ir(III)
complexes show dominant MC dd character in their T1 excited
state according to the aforementioned argument.
In contrast to the above approach, which is based on a full
geometry optimization for an isolated complex surrounded by
solvent molecules that mimic the diluted solution, the X-ray
structural data were also taken to perform the TDDFT
calculation to simulate the respective electronic properties in
solid state. Again, all results showed significant dd contribution
in the T1 excited state (see Figure S1 of the Supporting
Information). This can be confirmed by the Mulliken
population analysis,28 in which the net spin value is located
mainly on the Ir(III) metal atom. Therefore, for all titled
complexes the T1 state possesses a significant amount of MC
dd character; its repulsive PES, in theory, touches the ground-
state dissociation level, greatly facilitating the radiationless
deactivation or even weakening the metal−ligand bonds. Such
deactivation process is virtually barrierless and requires no
thermal activation, rationalizing the lack of emission even in the
77 K CH2Cl2 matrix.
Electrochemistry. The electrochemical behavior of these
Ir(III) metal complexes was investigated by cyclic voltammetry
as supplement to that obtained by spectroscopic and theoretical
measurements. These redox data are listed in Table 3. It is
notable that all electrochemical processes are irreversible which
is in good agreement with the higher absorption onset in the
UV/vis spectra and the larger energy gaps obtained in DFT
calculation. Despite their irreversibility, we can still extract
certain systematic trends, such as the reduction of the gap
between oxidation and reduction peak potentials for the
tripodal substituted phosphonite complexes 2b and 4b versus
that of phosphite complexes 2a and 4a, which could be due to
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Figure 10. Selected frontier orbitals involved in the lower-lying transition for 2b−6c.
the increased contribution of phenyl substituent of phosphonite
to the frontier orbitals. Furthermore, the thiocyanate complexes
5b and 6c show more positive oxidization peak potential versus
that of the chloride counterparts 4b and 2c. This could be
attributed to the relative poor π-donating property of the
thiocyanate ligand.26c
detachment of one chloride, giving the tripodal coordinated
Ir(III) complex [Ir(tpit)(PPh3)2Cl] (2a) in high yield, as the
representative example. Subsequent replacement of PPh3 and
PMe2Ph with chelating diphosphine and substitution of
chloride with thiocyanate are both feasible. Of particular
interest is the introduction of a second triphenylphosphite on
2a, which gives formation of [Ir(tpit)(tpitH)(PPh3)] (3a) with
all types of tripodal, bidentate, and monodentate phosphorus
donors coexisting on the Ir(III) coordination sphere. Due to
the lack of largely extended and/or heterocyclic ππ*
chromophores for these Ir(III) complexes, the 3MC dd
transition seems to be substantially incorporated into the T1
4. CONCLUSION
In sum, this study demonstrates the successful synthesis of a
series of Ir(III) complexes with phosphite (or phosphonite)
tripodal dicyclometalates. It appears that, in presence of two
equiv of PPh3, cyclometalation of phosphite (or phosphonite)
proceeds in a stepwise fashion, for which the first product, c.f.
[Ir(tpitH)(PPh3)2Cl2] (1a), shows a monocyclometalated
phosphite, with two PPh3 and two chlorides occupying mutual
trans and cis disposition. Further cyclometalation is concom-
itantly accompanied with trans-to-cis isomerization of PPh3 and
3
excited state. The repulsive PES of the resulting MC dd state,
in theory, should touch the PES of the ground state S0, giving
the dominant radiationless deactivation and hence virtually no
emission under all conditions.
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Table 2. Computational Energy Levels, Oscillator Strengths,
and Orbital Transition Analyses at S1 and T1 for 2a−6c
AUTHOR INFORMATION
Corresponding Author
*E-mail: ychi@mx.nthu.edu.tw (Y.C.), chop@ntu.edu.tw (P.-
T.C.).
■
λcal
f
assignment
2a
3a
4a
5a
2b
S1
T1
S1
T1
S1
T1
337.0
0.0012
HOMO → LUMO (43%)
HOMO-1 →LUMO (35%)
HOMO → LUMO (52%)
HOMO-1 → LUMO (17%)
HOMO → LUMO (69%)
HOMO-2 → LUMO (5%)
HOMO-7 → LUMO (80%)
HOMO-7 → LUMO+2 (6%)
HOMO → LUMO+2 (69%)
HOMO → LUMO (11%)
HOMO → LUMO+2 (50%)
HOMO → LUMO+6 (5%)
HOMO → LUMO (90%)
HOMO-5 → LUMO+2 (23%)
HOMO-4 → LUMO+3 (14%)
HOMO-8 → LUMO (9%)
HOMO → LUMO (78%)
HOMO-1 → LUMO (12%)
HOMO → LUMO (71%)
HOMO-1 → LUMO (11%)
HOMO → LUMO (91%)
HOMO → LUMO (82%)
HOMO-1 → LUMO+6 (6%)
HOMO → LUMO+3 (48%)
HOMO → LUMO+2 (33%)
HOMO → LUMO+1 (5%)
HOMO → LUMO+3 (67%)
HOMO → LUMO+2 (12%)
HOMO → LUMO+7 (7%)
HOMO → LUMO (90%)
HOMO-5 → LUMO+3 (33%)
HOMO-4 → LUMO+2 (21%)
HOMO-7 → LUMO (7%)
HOMO → LUMO (93%)
HOMO-2 → LUMO (22%)
HOMO-1 → LUMO (15%)
HOMO → LUMO (15%)
ACKNOWLEDGMENTS
■
353.0
330.7
342.6
336.6
350.9
0.0000
0.0566
0.0000
0.0167
0.0000
This work was supported by the National Science Council and
Ministry of Economy of Taiwan, project 100-EC-17-A-08-S1-
042. We are also grateful to the National Center for High-
Performance Computing for computer time and facilities.
DEDICATION
■
†Dedicated to Dr. Hubert Le Bozec on the occasion of his 60th
birthday.
REFERENCES
S1
334.8
346.4
0.0006
0.0000
■
T1
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S1
362.3
395.2
0.0008
0.0000
T1
2c
4b
S1
348.7
376.4
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0.0000
T1
S1
338.5
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T1
5b
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337.3
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320.8
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0.0014
0.0000
T1
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Table 3. Electrochemical Data of Ir (III) Complexes 2a−6c
ox
red
complex
Epa
Epc
2a
2b
2c
3a
4a
4b
5a
5b
6c
0.939
0.841
0.923
0.958
0.920
0.814
0.989
0.936
1.017
−2.936
−2.598
−2.582
−2.155
−2.707
−2.627
−2.667
−2.566
−2.567
a
The oxidation and reduction experiments were conducted in CH2Cl2
and THF solution, respectively; Epa and Epc are the anodic and
cathodic peak potentials referenced to the Fc+/Fc couple in V.
ASSOCIATED CONTENT
■
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S
* Supporting Information
Cyclic voltammogram and X-ray crystallographic data file
(CIF) of all studied complexes. This material is available free of
charge via the Internet at http://pubs.acs.org.
1794
dx.doi.org/10.1021/ic202090j | Inorg. Chem. 2012, 51, 1785−1795

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