Monometallic osmium(II) complexes with bis(N -methylbenzimidazolyl)benzene or -pyridine: A comparison study with ruthenium(II) analogues

Article abstract of DOI:10.1021/ic400385b

Seven bis-tridentate osmium complexes with Mebib or Mebip (Mebib is the 2-deprotonated form of 1,3-bis(N-methylbenzimidazolyl)benzene and Mebip is bis(N-methylbenzimidazolyl)pyridine) have been prepared, and their electrochemical and spectroscopic properties are compared with ruthenium structural analogues. Among them, four complexes have the [Os(NCN)(NNN)]-type coordination, including [Os(Mebib)(Mebip)](PF₆)₂ (1(PF₆)₂), [Os(dpb)(Mebip)](PF₆) (2(PF ₆), dpb is the 2-deprotonated form of 1,3-di(pyrid-2-yl)benzene), [Os(Mebib)(ttpy)](PF₆) (3(PF₆), ttpy = 4′-tolyl-2,2′:6′,2″-terpyridine), and [Os(dpb)(ttpy)](PF₆) (4(PF₆)). The other three complexes are [Os(Mebip)₂](PF₆)₂ (5(PF₆) ₂), [Os(Mebip)(tpy)](PF₆)₂ (6(PF ₆)₂, tpy = 2,2′:6′,2″-terpyridine), and [Os(ttpy)₂](PF₆)₂ (7(PF₆) ₂) with the [Os(NNN)(NNN)]-type coordination. Single crystals of 2(PF₆) and 6(PF₆)₂ have been obtained, and their structures are studied by X-ray crystallographic analysis. The Os(II/III) redox potentials of 1(PF₆)₂ to 7(PF₆) ₂ progressively increase from +0.04, +0.23, +0.24, +0.36, +0.56, +0.79 to +0.94 V vs Ag/AgCl, which are 200-300 mV less positive relative to the Ru(II/III) potentials of their ruthenium counterparts. The highest occupied molecular orbital energy levels of 1⁺-7²⁺ are calculated to vary in a descending order. The ruthenium and osmium complexes have singlet metal-to-ligand charge-transfer (MLCT) transitions of similar energies and band shapes, while the osmium complexes display additional ³MLCT transitions in the lower-energy region. Complexes 6(PF₆)₂ and 7(PF₆)₂ emit weakly at 780 and 740 nm, respectively. Complex 1(PF₆)₂ was synthesized as the oxidized Os(III) salt because of the low Os(II/III) potential. The transformation of 1 ²⁺ to 1⁺ by chemical reduction or electrolysis led to the emergence of the ¹MLCT transitions in the visible region.

Full text of DOI:10.1021/ic400385b

Article
pubs.acs.org/IC
Monometallic Osmium(II) Complexes with
Bis(N‑methylbenzimidazolyl)benzene or -pyridine: A Comparison
Study with Ruthenium(II) Analogues
Jiang-Yang Shao†,‡ and Yu-Wu Zhong*,†,§
†Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, China
‡University of Chinese Academy of Sciences, Beijing 100049, China
§State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, China
S
* Supporting Information
ABSTRACT: Seven bis-tridentate osmium complexes with
Mebib or Mebip (Mebib is the 2-deprotonated form of 1,3-
bis(N-methylbenzimidazolyl)benzene and Mebip is bis(N-
methylbenzimidazolyl)pyridine) have been prepared, and
their electrochemical and spectroscopic properties are
compared with ruthenium structural analogues. Among them,
four complexes have the [Os(NCN)(NNN)]-type coordina-
tion, including [Os(Mebib)(Mebip)](PF6)2 (1(PF6)2), [Os-
(dpb)(Mebip)](PF6) (2(PF6), dpb is the 2-deprotonated form of 1,3-di(pyrid-2-yl)benzene), [Os(Mebib)(ttpy)](PF6) (3(PF6),
ttpy = 4′-tolyl-2,2′:6′,2″-terpyridine), and [Os(dpb)(ttpy)](PF6) (4(PF6)). The other three complexes are [Os(Mebip)2](PF6)2
(5(PF6)2), [Os(Mebip)(tpy)](PF6)2 (6(PF6)2, tpy = 2,2′:6′,2″-terpyridine), and [Os(ttpy)2](PF6)2 (7(PF6)2) with the
[Os(NNN)(NNN)]-type coordination. Single crystals of 2(PF6) and 6(PF6)2 have been obtained, and their structures are
studied by X-ray crystallographic analysis. The Os(II/III) redox potentials of 1(PF6)2 to 7(PF6)2 progressively increase from
+0.04, +0.23, +0.24, +0.36, +0.56, +0.79 to +0.94 V vs Ag/AgCl, which are 200−300 mV less positive relative to the Ru(II/III)
potentials of their ruthenium counterparts. The highest occupied molecular orbital energy levels of 1+−72+ are calculated to vary
in a descending order. The ruthenium and osmium complexes have singlet metal-to-ligand charge-transfer (MLCT) transitions of
similar energies and band shapes, while the osmium complexes display additional 3MLCT transitions in the lower-energy region.
Complexes 6(PF6)2 and 7(PF6)2 emit weakly at 780 and 740 nm, respectively. Complex 1(PF6)2 was synthesized as the oxidized
Os(III) salt because of the low Os(II/III) potential. The transformation of 12+ to 1+ by chemical reduction or electrolysis led to
1
the emergence of the MLCT transitions in the visible region.
anionic cyclometalating ligand, the metal center of cyclo-
metalated complexes is much more electron-rich with respect
to the noncyclometalated analogues, and the metal-associated
redox potentials are significantly decreased.
INTRODUCTION
■
Transition-metal polyazine complexes have attracted enormous
attention because of their superior electrochemical and
photophysical properties.1 Among them, cyclometalated
complexes are one special type of material that have been the
focus of much research efforts.2 These complexes feature a M−
C bond between the metal center and a carbon anionic ligand,
for example, the CN-type bidentate ligand or the CNN- or
NCN-type tridentate ligand. Transition metals that are mostly
involved in cyclometalated complexes include ruthenium,3
iridium,4 and platinum.5 These complexes are very useful in a
wide range of applications, such as light-emitting devices,6 solar
cells,7 and mixed-valence chemistry.8
In some applications, the redox potentials of complexes play
a crucial role in determining their performance. For instance,
low operational potentials would be beneficial for electro-
chromism (reversible absorption spectral changes in response
to external electric field) and would improve the device stability
and memory time.9 In this sense, the use of cyclometalated
complexes is very effective. Because of the presence of the
Recently, we have reported on a series of cyclometalated
ruthenium complexes with the 2-deprotonated form of 1,3-
bis(N-methylbenzimidazolyl)benzene (MebibH) and bis(N-
methylbenzimidazolyl)pyridine (Mebip).10 These complexes
display low Ru(II/III) potentials as a result of the electron-
donating nature of the carbon anionic ligand and the
benzimidazole units. For instance, the Ru(II/III) process of
complex [Ru(Mebib)(Mebip)](PF6) takes places at +0.26 V vs
Ag/AgCl, which is considerably lower with respect to the
cyclometalated complex [Ru(dpb)(tpy)](PF6) (E1/2 = 0.56 V)
and the noncyclometalated complex [Ru(tpy)2](PF6)2 (E1/2
=
1.32 V), where dpb is the 2-deprotonated form of 1,3-di(pyrid-
2-yl)benzene (dpbH) and tpy is 2,2′:6′,2″-terpyridine. As an
Received: February 13, 2013
© XXXX American Chemical Society
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Scheme 1. Syntheses of Compounds Studied
extension of this work, we considered that the use of osmium
would be possible to further decrease the metal-based redox
potentials. Osmium polyazine complexes have been well-known
to possess well-defined Os(II/III) processes with much lower
redox potentials relative to ruthenium structural analogues.11
Compared to cyclometalated ruthenium complexes, only
limited reports have been devoted to the syntheses and studies
of cyclometalated osmium complexes.12 Le Lagadec and
Ryabov and co-workers have synthesized a series of cyclo-
complexes with Mebip or Mebib (Scheme 1) and a comparison
study of their electrochemical and spectroscopic properties with
the previously reported ruthenium analogues.10a In addition,
theoretical calculations have been performed to complement
these experimental results.
RESULTS AND DISCUSSION
■
Syntheses and X-ray Structures. The osmium complexes
studied in the paper were synthesized as outlined in Scheme 1.
The reaction of (NH4)2[OsCl6] with Mebip afforded
[(Mebip)OsCl3] in good yield. The treatment of [(Mebip)-
OsCl3] with MebibH in ethylene glycol under microwave
heating, followed by anion exchange using KPF6, gave complex
[Os(Mebib)(Mebip)](PF6)2 (1(PF6)2) in 23% yield. This
reaction was expected to give a cyclometalated Os(II) complex
with one anion. However, only the oxidized Os(III) form was
isolated, suggesting that the Os(II/III) potential is sufficiently
low. The identity of 1(PF6)2 was supported by mass spectrum,
microanalysis, and following spectroelectrochemical measure-
ment. Using a similar procedure, the reaction of [(Mebip)Os-
Cl3] with dpbH, Mebip, and tpy gave the cyclometalated
complex [Os(dpb)(Mebip)](PF6) (2(PF6)) and noncyclome-
talated complexes [Os(Mebip)2](PF6)2 (5(PF6)2) and [Os-
(Mebip)(tpy)](PF6)2 (6(PF6)2), respectively. Cyclometalated
complexes [Os(Mebib)(ttpy)](PF6) (3(PF6), ttpy = 4′-tolyl-
2,2′:6′,2″-terpyridine)17 and [Os(dpb)(ttpy)](PF6) (4(PF6))
metalated osmium complexes with a general formula of
m+
[Os(C−N)x(N−N)3−x
]
(x = 0−3),13 where C−N is a
bidentate cyclometalating ligand and N−N is a bidentate
ligand, such as 2,2′-bipyridine and 1,10-phenanthroline. These
complexes have low redox potentials and high rates of oxidation
of reduced enzymes. Collin and Barigelletti and co-workers
reported a few [Os(NCN)(NNN)]-type bis-tridentate poly-
pyridyl osmium complexes and related dimetallic complexes
bridged by a biscyclometalating ligand.14 Recently, some
emissive osmium complexes supported by N-heterocyclic
carbene-based CCC-pincer ligands and aromatic diimines
have been disclosed by Wong and co-workers.15 We note
that, although a large number of transition-metal complexes
with Mebip or Mebib have been known,16 osmium complexes
with these two ligands, either cyclometalated or noncyclometa-
lated, have not been documented to date. We present in this
Article the syntheses and characterization of a series of osmium
B
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Figure 1. Thermal ellipsoid plots of the X-ray structures of (a) 2(PF6) and (b) 6(PF6)2 with 30% probability. Counter anions and hydrogen atoms
are omitted for clarity. Atom color code: carbon, gray; nitrogen, blue; osmium, brown.
were prepared from the reaction of [(ttpy)OsCl3]14 with
MebibH and dpbH, respectively. The yields for the syntheses of
these complexes are in the range of 20−30%. Some byproducts
with higher polarity were detected in thin-layer chromatog-
raphy. However, their composition has not been identified. The
addition of AgOTf in these reactions, as has been used in the
syntheses of ruthenium analogues,10 did not improve the yield.
In addition to these complexes, a known compound [Os-
(ttpy)2](PF6)2 (7(PF6)2) was prepared for a comparison
study.18
Single crystals of 2(PF6) and 6(PF6)2 suitable for X-ray
analysis were obtained by diffusion of diethyl ether into the
solution of these two compounds in CH3CN. The thermal
ellipsoid plots of the X-ray structures are shown in Figure 1.
Crystal data and selected bond lengths and angles are given in
Tables 1 and 2. The bis-tridentate coordination mode is
confirmed for both complexes. In complex 2(PF6), the Mebib
ligand binds to osmium with an NCN-type coordination. The
Os−C1 bond length is 1.977(8) Å. The Os−N bonds are in the
range of 2.058(4)−2.087(7) Å. In complex 6(PF6)2, the bond
between osmium and the central pyridine nitrogen (N6) of tpy
is the shortest Os−N bond in length. The Os−N3 bond,
opposite to Os−N6, has a length of 2.023(6) Å. Other Os−N
bonds are in the range of 2.060(6)−2.072(6) Å.
Electrochemical Studies. Figure 2 shows the cyclic
voltammograms (CVs) of the above synthesized osmium
complexes. The electrochemical data are summarized in Table
3, together with those of the previously reported ruthenium
analogues.10a Cyclometalated complexes 1(PF6)2 to 4(PF6)
show one cathodic wave at −1.63, −1.57, −1.53, and −1.48 V
vs Ag/AgCl, respectively. They are assigned to the reduction of
the individual noncyclometalating (NNN) ligand, Mebip of
1(PF6)2 and 2(PF6), and ttpy of 3(PF6) and 4(PF6),
respectively. The anionic cyclometalating (NCN) ligand is
more electron-rich and thus sluggish to be reduced relative to
the NNN ligand. Within the solvent window, complexes
1(PF6)2 to 4(PF6) all display two peaks in the anodic scan. The
less positive redox couples at +0.04, +0.23, +0.24, and +0.36 V
vs Ag/AgCl for 1(PF6)2 to 4(PF6), respectively, are attributed
to the Os(II/III) processes. It is possible that some mixing of
ligand oxidation is involved in this process, a common feature
for cyclometalated complexes.3 It is not surprising that complex
1(PF6)2 was isolated in the oxidized form because of its low
Os(II/III) potential. The more positive redox waves of 1(PF6)2
to 4(PF6) (mostly irreversible except 1(PF6)2) are ascribed to
the Os(III/IV) processes.
Table 1. Crystallographic Data
Noncyclometalated complexes 5(PF6)2 to 7(PF6)2 all show
two ligand-based reduction waves. The Os(II/III) process
occurs at +0.56, +0.79, and +0.94 V vs Ag/AgCl for 5(PF6)2,
6(PF6)2, and 7(PF6)2, respectively. The Os(II/III) potentials
for noncyclometalated complexes are clearly more positive with
respect to cyclometalated complexes 1(PF6)2 to 4(PF6). The
Os(II/III) potentials of osmium complexes 1(PF6)2 to 7(PF6)2,
either cyclometalated or not, are 200−300 mV less positive
relative to the Ru(II/III) potentials of their ruthenium
counterparts (Table 3). This is caused by the lower third
ionization energy for Os relative to Ru.11
Density Functional Theory (DFT) Calculations. DFT
calculations were performed for 1+−72+ on the B3LYP/
LANL2DZ/6-31G*/CPCM level of theory (see details in the
Experimental Section). Figure 3 shows the calculated energy
diagrams of these complexes. The highest occupied molecular
orbital (HOMO) levels progressively descend from −4.66 eV
for 1+ to −5.88 eV for 72+. This order is in good accordance
compound
2(PF6)
6(PF6)2
empirical formula
formula weight
space group
crystal system
a (Å)
C37H28N7OsPF6
905.83
C36H28N8OsP2F12
1052.81
P1
̅
P1
̅
triclinic
9.257(2)
11.733(3)
17.132(5)
97.50
triclinic
13.1990(18)
18.001(3)
18.683(2)
95.03
b (Å)
c (Å)
α (deg)
β (deg)
99.13
90.19
γ (deg)
vol (Å3)
111.02
1679.1(7)
2
104.01
4289.0(10)
2
Z
R1 (all)
0.0531
0.0458
0.1529
0.1249
0.0749
R1 (gt)
0.0594
wR2 (ref)
wR2 (gt)
0.1853
0.1734
C
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Table 2. Selected Bond Lengths and Bond Angles
bond lengths (Å)
bond angles (deg)
2(PF6)
6(PF6)2
2(PF6)
6(PF6)2
Os−N(1) 2.074(6)
Os−N(2) 2.061(5)
Os−N(3) 2.066(6)
Os−N(4) 2.058(4)
Os−N(5) 2.087(7)
Os−C(1) 1.977(8)
Os−N(1) 2.070(5)
Os−N(2) 2.072(6)
Os−N(3) 2.023(6)
Os−N(4) 2.065(6)
Os−N(5) 2.060(6)
Os−N(6) 1.993(5)
C(1)−Os−N(1) 77.9(3)
C(1)−Os−N(2) 101.8(3)
C(1)−Os−N(3) 178.8(3)
N(3)−Os−N(1) 102.3(2)
N(3)−Os−N(2) 77.0(2)
N(6)−Os−N(1) 78.2(2)
N(6)−Os−N(2) 104.6(2)
N(6)−Os−N(3) 177.5(2)
N(3)−Os−N(1) 102.1(2)
N(3)−Os−N(2) 77.9(2)
Figure 3. DFT-calculated energy diagrams of 1+−72+. The numbers
shown in the middle indicate the LUMO and HOMO energies.
except that the HOMO−1 has some contributions from the
cyclometalating phenyl ring. The much lower-lying HOMO−3,
HOMO−4, and HOMO−5 are dominated by the NCN ligand
(Mebib) and NNN (Mebip) ligand, respectively. The closely
spaced LUMO and LUMO+1 of 1+ have major contributions
from the NNN ligand and a minor contribution from the
osmium atom. This feature has not been observed for
cyclometalated ruthenium complexes,10 reflecting the greater
extension of osmium d orbitals.11 However, it should be kept in
mind that DFT calculations tend to overestimate electron
delocalization. The higher-lying LUMO+2 level is dominated
by the NCN ligand. Other three cyclometalated complexes
(2+−4+) have very similar frontier orbital orderings and
Figure 2. (a) CVs of 1(PF6)2 to 7(PF6) (anions are omitted for
complex labels) in 0.1 M Bu4NClO4/CH3CN at 100 mV/s. (b) A
comparison of the Os(II/III) waves.
with the Os(II/III) potentials of these complexes (Figure 2 and
Table 3). The lowest unoccupied molecular orbital (LUMO)
levels of these complexes have the same descending order from
1+ to 72+, which also correlates well with the first reduction
potentials of these complexes.
The closely spaced HOMO, HOMO−1, and HOMO−2 of
1+ have major contributions from the osmium atom (Figure 4),
Table 3. Electrochemical and Absorption Data
a
b
b
c
complex
E1/2 (anodic)
E1/2 (cathodic)
λmax/nm (ε/105 M−1 cm−1
)
[Os(Mebib)(Mebip)]2+, 12+
+0.04, +1.13
+0.26, +1.50
−1.63
−1.60
−1.57
−1.56
−1.53
−1.55
−1.48
−1.51
−1.22, −1.60
−1.24, −1.55
−1.20, −1.53
−1.24, −1.50
−1.17, −1.45
−1.22, −1.46
354 (0.23), 510 (0.16), 590 (0.057)
d
[Ru(Mebib)(Mebip)]+
334 (0.32), 353 (0.27), 515 (0.13), 571 (0.077)
350 (0.32), 450 (0.13), 510 (0.16), 800 (0.011)
334 (0.29), 339 (0.39), 457 (0.12), 516 (0.17)
396 (0.17), 470 (0.19), 514(0.18), 864 (0.021)
275 (0.47), 319 (0.44), 394 (0.082), 497 (0.11)
372 (0.20), 502 (0.20), 538 (0.19), 764 (0.025)
372 (0.086), 423 (0.095), 499 (0.14)
360 (0.71), 486 (0.20), 564 (0.071), 798 (0.018)
357 (0.66), 491 (0.16)
e
[Os(dpb)(Mebip)]+, 2+
+0.23, +1.18
d
e
[Ru(dpb)(Mebip)]+
+0.43, +1.49
e
[Os(Mebib)(ttpy)]+, 3+
+0.24, +1.17
d
[Ru(Mebib)(tpy)]+
+0.48, +1.47
e
[Os(dpb)(ttpy)]+, 4+
+0.36, +1.27
df
e
,
[Ru(dpb)(tpy)]+
+0.56, +1.60
[Os(Mebip)2]2+, 52+
+0.56, +1.67
+0.86
d
[Ru(Mebip)2]2+
e
[Os(Mebip)(tpy)]2+, 62+
+0.79, +1.81
356 (0.39), 480 (0.15), 542 (0.063), 718 (0.028)
354 (0.38), 480 (0.14)
d
[Ru(Mebip)(tpy)]2+
+1.07
+0.94
+1.32
[Os(ttpy)2]2+, 72+
314 (0.72), 490 (0.25), 668 (0.064)
df
,
[Ru(tpy)2]2+
307 (0.78), 475 (0.17)
a
b
−
All anions are PF6 . The potential is reported as the E1/2 value vs Ag/AgCl. The potential value vs ferrocene0/+ can be deduced by subtracting 0.45
c
d
e
f
V. All absorption spectra were recorded in CH3CN at room temperature. See ref 10a. Ep,anodic, irreversible. See ref 3i.
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Figure 4. Selected frontier orbital graphics of 1+. The upper and lower parts of the structure are Mebib and Mebip, respectively.
compositions as 1+ (Figures S1−S3 in the Supporting
Information), except that the HOMOs, instead of HOMO−1,
of 2+−4+ have some contributions from the cyclometalating
phenyl ring. These calculation results support the previous
electrochemical assignment that the observed cathodic waves of
12+−4+ are associated with their NNN ligands, and the first
anodic waves are the OsII/III processes, possibly mixing with
some portion of ligand oxidation.
Selected frontier orbitals with electron density distributions
of the noncyclometalated complexes 52+−72+ are provided in
Figures S4−S6 (Supporting Information). Complexes 52+ and
72+ have symmetrical structures, and their occupied and
unoccupied frontier orbitals are dominated by osmium and
individual ligands, respectively. For the asymmetric complex
62+, the LUMO and LUMO+1 are dominated by Mebip and
tpy ligands, respectively (Figure S5, Supporting Information).
Spectroscopic Studies and Time-Dependent DFT
(TDDFT) Calculations. The UV/vis absorption spectra of 1+
to 7(PF6)2 (1+ was obtained by chemical reduction; see below)
are displayed in Figure 5, and the absorption data are
summarized in Table 3. Complexes 1+, 2(PF6), 5(PF6)2, and
Figure 5. UV/vis absorption spectra of (a) cyclometalated complexes
1+ to 4(PF6) and (b) noncyclometalated complexes 5(PF6)2 to
7(PF6)2 in CH3CN. Anions are omitted for the complex labels for
clarity.
6(PF6)2 show intense Mebip-based intraligand (IL) transitions
around 350 nm. Other IL transitions locate at a slightly higher-
energy region. This feature has previously been observed for
the ruthenium complexes with Mebip.10a Absorption bands in
the visible region are due to the singlet metal-to-ligand charge-
transfer (1MLCT) transitions. Most complexes, especially
3(PF6) to 7(PF6)2, show distinct shallow absorption in the
region of 650−900 nm. These are ascribed to the spin-
forbidden 3MLCT transitions, a well-known feature for
polyazine osmium complexes caused by the strong spin−orbital
coupling of osmium.11−14 The solvent dependence of the
absorption spectra of both cyclometalated and noncyclometa-
lated complexes, represented by 2(PF6) and 6(PF6)2, are
insignificant (Figures S7 and S8, Supporting Information).
absorption maximum at 440 nm. These four excitations are
mainly of the HOMO−2 → LUMO+1, HOMO → LUMO+2,
HOMO−1 → LUMO+2, and HOMO−2 → LUMO character,
respectively, where LUMO and LUMO+1 have dominant
contributions from the NNN ligand and LUMO+2 from the
NCN ligand. Symmetrical noncyclometalated complexes
1
5(PF6)2 and 7(PF6)2 display MLCT absorption maxima at
486 and 490 nm, respectively. For the asymmetric complex 62+,
TDDFT results suggest that the 1MLCT transitions are
associated both Mebip and ttpy ligands.
1
The MLCT transitions of cyclometalated complexes are
much more broad and complex with respect to those of
noncyclometalated complexes. To assist the understanding of
these transitions, TDDFT calculations have been performed for
the singlet states of asymmetric complexes 1+, 2+, 3+, 4+, and
62+ (Figure 6, and Table S1 in the Supporting Information).
These results suggest that the MLCT bands of 1+−4+ are all
associated with both NCN and NNN ligands. For example, the
calculated S5 and S6 excitations of 1+ are responsible for the
observed shoulder band around 520 nm and S7 and S8
excitations are responsible for the MLCT band with the
Figure S9 in the Supporting Information provides a
comparison of the absorption spectra of the Os series
complexes with their ruthenium counterparts (Ru series).
Two series compounds have similar 1MLCT absorption shapes
3
and energies, but no MLCT transitions are observed for the
Ru series compounds. Complexes 3(PF6), 4(PF6), and 7(PF6)2
1
have a slightly higher MLCT molar absorptivity relative to
their ruthenium counterparts, [Ru(Mebib)(tpy)](PF6), [Ru-
(dpb)(tpy)](PF6), and [Ru(tpy)2](PF6)2, respectively. This is
partially caused by the use of one different auxiliary ligand, tpy
E
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Figure 6. UV/vis absorption spectra (black curves) and TDDFT-predicted singlet excitations (vertical lines and red dotted curves) of (a) 1+, (b) 2+,
(c) 3+, (d) 4+, and (e) 62+. The left and right y axes are associated with the absorption spectra and predicted excitations, respectively.
for the Ru series and ttpy for the Os ttpy series. Complex
7(PF6)2 was previously reported to show an emission band
around 750 nm at room temperature.18a Similarly, we have
recorded a weak emission at 740 nm for this complex (Figure
7). In addition, the asymmetric noncyclometalated complex
6(PF6)2 was found to emit weakly at 780 nm. However, no
distinct emission was detected for other complexes.
Figure 8. Absorption spectral changes of 1(PF6)2 in CH3CN during
stepwise reduction with NH2NH2·H2O.
containing the Mebib or Mebip ligands. The Os(II/III)
potentials of these complexes can be modulated in a wide
range from +0.04 to +0.94 V vs Ag/AgCl, which are 200−300
mV less positive relative to the Ru(II/III) potentials of their
ruthenium counterparts. This feature may make osmium
complexes applicable for redox-controlled processes, such as
mixed-valence chemistry,8,10b electrochromism,9 and electro-
catalysis.13 The newly prepared osmium complexes show
absorption in the near-infrared (NIR) region due to the
3MLCT transitions, and they can be considered as potential
dyes for solar cell applications. In this sense, the cyclometalated
complexes are of little interest, because their HOMO levels are
too high for dye regeneration.7 It would be better to design dye
compounds on the basis of the noncyclometalated complexes
with lower-lying HOMO levels.
Figure 7. Emission spectra of 6(PF6)2 (red line) and 7(PF6)2 (black
line) in CH3CN at room temperature. The excitation wavelength is
480 nm.
As has been mentioned earlier, 1(PF6)2 was isolated as the
Os(III) form. When 1(PF6)2 was treated with aqueous
hydrazine (NH2NH2·H2O) in CH3CN,19 the absorption band
1
at 420 nm decreased and the MLCT transition at 510 nm,
associated with the reduced form 1+, was recovered (Figure 8).
The appearance of isosbestic absorption points at 338 and 460
nm indicates the clean transformation of this process. The
reduction of 1(PF6)2 can also be triggered by electrolysis with
an indium tin oxide (ITO) glass electrode by gradually
decreasing the potential from the open-circuit potential to
−0.6 V vs Ag/AgCl (Figure S10, Supporting Information).
EXPERIMENTAL SECTION
■
General Procedure. NMR spectra were recorded in designated
solvents on a Bruker Avance 400 MHz spectrometer. Spectra are
reported in parts per million values from residual protons of
deuterated solvents. Mass spectra (MS) data were obtained with a
Bruker Daltonics Inc. ApexII FT-ICR or Autoflex III MALDI-TOF
mass spectrometer. The matrix is α-cyano-4-hydroxycinnamic acid.
Microanalysis was carried out using a Flash EA 1112 analyzer at the
Institute of Chemistry, Chinese Academy of Sciences. Mebip,10a
CONCLUSION
In summary, we have successfully prepared a series of
cyclometalated and noncyclometalated osmium complexes
■
F
dx.doi.org/10.1021/ic400385b | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
MebibH,10a ttpy,17 dpbH,20 and [Os(ttpy)2](PF6)2 were prepared
18
according to known procedures.
was obtained from the reaction of [(Mebip)OsCl3] (31.8 mg, 0.050
mmol) and tpy (20.1 mg, 0.080 mmol) in 30% yield. H NMR (400
1
Synthesis of [Os(Mebip)Cl3]. To 10 mL of dry N,N-dimethyl
formamide were added (NH4)2[OsCl6] (207.8 mg, 0.47 mmol) and
Mebip (176.1 mg, 0.52 mmol). The mixture was refluxed for 1 h. After
cooling to room temperature, the mixture was poured into 30 mL of
ethyl ether. The resulting precipitate was collected by filtering and
washing with ethyl ether to give 214 mg of [Os(Mebip)Cl3] as a black
solid in 70% yield. MALDI-MS: 601.0 for [M − Cl]+.
MHz, CD3CN): δ 4.52 (s, 6H), 5.94 (d, J = 8.4 Hz, 2H), 6.93 (m,
2H), 7.02 (m, 2H), 7.25 (d, J = 5.6 Hz, 2H), 7.38 (m, 2H), 7.54 (d, J =
8.4 Hz, 2H), 7.61 (m, 2H), 7.76 (t, J = 8.4 Hz, 1H), 7.97 (t, J = 8.2 Hz,
1H), 8.35 (d, J = 8.0 Hz, 2H), 8.70 (d, J = 8.4 Hz, 2H), 8.82 (d, J = 8.4
Hz, 2H). MALDI-MS: 908.5 for [M − PF6]+, 762.4 for [M − 2PF6]+.
Anal. Calcd for C36H28F12N8P2Os·H2O: C, 40.38; H, 2.82; N, 10.46.
Found: C, 39.98; H, 2.91; N, 10.83.
Synthesis of [Os(ttpy)Cl3]. To 10 mL of dry N,N-dimethyl
formamide were added (NH4)2[OsCl6] (219 mg, 0.50 mmol) and ttpy
(161 mg, 0.52 mmol). The mixture was refluxed for 1 h. After cooling
to room temperature, the mixture was poured into 30 mL of ethyl
ether. The resulting precipitate was collected by filtering and washing
with ethyl ether to give 252 mg of [Os(ttpy)Cl3] as a black solid in
81% yield. MALDI-MS: 584.9 for [M − Cl]+.
Synthesis of Complex [Os(Mebib)(Mebip)](PF6)2, 1(PF6)2. To
10 mL of dry ethylene glycol were added [(Mebip)OsCl3] (34.5 mg,
0.054 mmol) and MebibH (16.9 mg, 0.050 mmol). The mixture was
refluxed for 0.5 h under microwave heating (power = 375 W). After
cooling to room temperature, an excess of aq. KPF6 was added. The
resulting precipitate was collected by filtrating and washing with water
and Et2O. The obtained solid was subjected to flash column
chromatography on silica gel (eluent: CH3CN/H2O/aq. KNO3,
100/5/0.5), followed by anion exchange with KPF6, to give 11.4 mg
of 1(PF6)2 in 23% yield as a black solid. MALDI-MS: 868.5 for [M −
2PF6]+. Anal. Calcd for C43H34F12N9P2Os·H2O: C, 43.96; H, 3.09; N,
10.73. Found: C, 43.84; H, 3.28; N, 10.72.
Electrochemical Measurements. All CV measurements were
taken using a CHI620D potentiostat with a one-compartment
electrochemical cell under an atmosphere of nitrogen. All measure-
ments were carried out in denoted solvents containing 0.1 M
nBu4NClO4 as the supporting electrolyte at a scan rate of 100 mV/s.
The working electrode was a glassy carbon with a diameter of 3 mm.
The electrode was polished prior to use with 0.05 μm alumina and
rinsed thoroughly with water and acetone. A large area platinum wire
coil was used as the counter electrode. All potentials are referenced to
the Ag/AgCl electrode in saturated aqueous NaCl without regard for
the liquid junction potential. Potentials vs ferrocene0/+ can be deduced
by subtracting 0.45 V.
Spectroscopic Measurements. UV−vis and NIR spectra were
recorded on a TU-1810DSPC or a PE Lambda 750 UV/vis/NIR
spectrophotometer at room temperature in CH3CN, with a conven-
tional 1 cm quartz cell. Emission spectra were recorded using an F-380
spectrofluorimeter of Tianjin Gangdong Sic. & Tech Development Co.
Ltd., with a red-sensitive photomultiplier tube R928F. Spectroelec-
trochemistry was performed in a thin layer cell (optical length = 0.1
cm) in which an ITO glass working electrode was set. A platinum wire
and Ag/AgCl in saturated aqueous NaCl was used as a counter
electrode and a reference electrode, respectively. The cell was put into
the spectrometer to monitor the spectral change during electrolysis.
X-ray Crystallography. The X-ray diffraction data were collected
using a Rigaku Saturn 724 diffractometer on a rotating anode (Mo−K
radiation, 0.71073 Å) at 173 K. The structure was solved by the direct
method using SHELXS-9721 and refined with Olex2.22 The structure
graphics shown in shown in Figure 1 were generated using Olex2. The
corresponding CIF files are provided in the Supporting Information.
Computational Methods. All calculations were implemented in
the Gaussian 09 program.23 Wave functions were expanded in the
LANL2DZ basis set with effective core potentials,24 and electron
exchange-correlation was described using the B3LYP hybrid func-
tional.25 No symmetry constraints were used in the optimization
(nosymm keyword was used). Solvation effects in CH3CN were
included using the conductor-like polarizable continuum model
(CPCM) with united-atom Kohn−Sham (UAKS) radii.26 Frequency
calculations have been performed with the same level of theory to
ensure the optimized geometries to be local minima. All orbitals have
been computed at an isovalue of 0.03 e/bohr3. The TDDFT-predicted
spectra were generated using GaussView 5.0.
Synthesis of Complex [Os(Mebip)(dpb)](PF6), 2(PF6). Using
the same procedure for the synthesis of 1(PF6)2, 12.2 mg of complex
2(PF6) was isolated from the reaction of [(Mebip)OsCl3] (32.5 mg,
1
0.051 mmol) with dpbH (18.5 mg, 0.080 mmol) in 26% yield. H
NMR (400 MHz, CD3CN): δ 4.54 (s, 6H), 5.98 (d, J = 8.0 Hz, 2H),
6.46 (t, J = 6.4 Hz, 2H), 6.75 (t, J = 8.0 Hz, 2H), 6.86 (m, 2H), 7.28 (t,
J = 7.4 Hz, 4H), 7.46 (d, J = 8.0 Hz, 4H), 8.04 (d, J = 8.4 Hz, 2H),
8.43 (d, J = 7.6 Hz, 2H), 8.54 (m, 2H). MALDI-MS: 762.4 for [M −
PF6]+. Anal. Calcd for C37H28F6N7POs: C, 49.06; H, 3.12; N, 10.82.
Found: C, 49.15; H, 3.09; N, 10.78.
Synthesis of Complex [Os(Mebib)(ttpy)](PF6), 3(PF6). Using
the same procedure for the synthesis of 1(PF6)2, 14.0 mg of 3(PF6)
was isolated from the reaction of [(ttpy)OsCl3] (32.0 mg, 0.052
1
mmol) and MebibH (17.0 mg, 0.050 mmol) in 28% yield. H NMR
(400 MHz, CD3CN): δ 2.56 (s, 3H), 4.45 (s, 6H), 5.35 (t, J = 7.2 Hz,
1H), 5.58 (s, 2H), 6.70 (t, J = 7.6 Hz, 2H), 6.96−7.06 (m, 4H), 7.24−
7.36 (m, 8H), 7.55 (d, J = 8.0 Hz, 2H), 8.14 (d, J = 7.2 Hz, 2H), 8.49
(d, J = 8.0 Hz, 2H), 8.94 (s, 2H). MALDI-MS: 852.6 for [M − PF6]+.
Anal. Calcd for C44H34F6N7POs: C, 53.06; H, 3.44; N, 9.84. Found: C,
53.29; H, 3.64; N, 10.10.
Synthesis of Complex [Os(ttpy)(dpb)](PF6), 4(PF6).14 Using
the same procedure for the synthesis of 1(PF6)2, 10.8 mg of 4(PF6)
was isolated from the reaction of [(ttpy)OsCl3] (31.2 mg, 0.050
mmol) and dpbH (17.0 mg, 0.050 mmol) in 24% yield. 1H NMR (400
MHz, CD3CN): δ 2.53 (s, 3H), 6.55 (t, J = 6.2 Hz, 2H), 6.86−6.92
(m, 4H), 7.11 (d, J = 4.4 Hz, 2H), 7.30 (s, 1H), 7.46 (t, J = 7.0 Hz,
2H), 7.53 (d, J = 7.6 Hz, 2H), 7.58 (t, J = 7.2 Hz, 2H), 8.06 (d, J = 8.4
Hz, 2H), 8.17 (d, J = 8.0 Hz, 2H), 8.35 (d, J = 7.6 Hz, 2H), 8.57 (d, J
= 8.0 Hz, 2H), 8.99 (s, 2H). MALDI-MS: 744.4 for [M − PF6]+. Anal.
Calcd for C38H28F6N5POs·3H2O: C, 48.35; H, 3.63; N, 7.42. Found:
C, 48.43; H, 3.27; N, 7.54.
ASSOCIATED CONTENT
■
S
* Supporting Information
X-ray crystallographic data for 2(PF6) and 6(PF6)2 in CIF
format, isodensity plots of frontiers orbitals, TDDFT results,
Cartesian coordinates for DFT-optimized structures, and NMR
and mass spectra of new complexes. This material is available
free of charge via the Internet at http://pubs.acs.org.
Synthesis of Complex [Os(Mebip)2](PF6)2, 5(PF6)2. Using the
same procedure for the synthesis of 1(PF6)2, 10.9 mg of 5(PF6)2 was
isolated from the reaction of [(Mebip)OsCl3] (31.9 mg, 0.050 mmol)
and Mebip (17.5 mg, 0.050 mmol) in 19% yield. 1H NMR (400 MHz,
CD3CN): δ 4.52 (s, 12H), 6.17 (d, J = 8.4 Hz, 4H), 6.92 (t, J = 7.6 Hz,
4H), 7.35 (t, J = 7.8 Hz, 4H), 7.42 (d, J = 8.4 Hz, 4H), 7.73 (d, J = 8.4
Hz, 2H), 8.76 (d, J = 8.4 Hz, 4H). MALDI-MS: 1014.5 for [M −
PF6]+, 870.5 for [M − 2PF6]+. Anal. Calcd for C42H34F12N10P2Os·
H2O: C, 42.86; H, 3.08; N, 11.90. Found: C, 42.98; H, 3.40; N, 11.80.
Synthesis of Complex [Os(Mebip)(tpy)](PF6)2, 6(PF6)2. Using
the same procedure for the synthesis of 1(PF6)2, 15.8 mg of 6(PF6)2
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: zhongyuwu@iccas.ac.cn.
Notes
The authors declare no competing financial interest.
G
dx.doi.org/10.1021/ic400385b | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(8) (a) Beley, M.; Collin, J.-P.; Louis, R.; Metz, B.; Sauvage, J.-P. J.
Am. Chem. Soc. 1991, 113, 8521. (b) Sutter, J.-P.; Grove, D. M.; Beley,
M.; Collin, J.-P.; Veldman, N.; Spek, A. L.; Sauvage, J.-P.; van Koten,
G. Angew. Chem., Int. Ed. 1994, 33, 1282. (c) Patoux, C.; Launay, J.-P.;
Beley, M.; Chodorowski-Kimmers, S.; Collin, J.-P.; James, S.; Sauvage,
J.-P. J. Am. Chem. Soc. 1998, 120, 3717. (d) Steenwinkel, P.; Grove, D.
M.; Veldman, N.; Spek, A. L.; van Koten, G. Organometallics 1998, 17,
5647. (e) Fraysse, S.; Coudret, C.; Launay, J.-P. J. Am. Chem. Soc.
2003, 125, 5880. (f) Gagliardo, M.; Amijs, C. H. M.; Lutz, M.; Spek, A.
L.; Havenith, R. W. A.; Hartl, F.; van Klink, G. P. M.; van Koten, G.
Inorg. Chem. 2007, 46, 11133. (g) Yang, W.-W.; Yao, J.; Zhong, Y.-W.
Organometallics 2012, 31, 1035. (h) Yao, C.-J.; Zhong, Y.-W.; Yao, J. J.
Am. Chem. Soc. 2011, 133, 15697. (i) Yao, C.-J.; Sui, L.-Z.; Xie, H.-Y.;
Xiao, W.-J.; Zhong, Y.-W.; Yao, J. Inorg. Chem. 2010, 49, 8347.
(9) (a) Mortimer, R. J. Chem. Soc. Rev. 1997, 26, 147. (b) Ward, M.
D. J. Solid State Electrochem. 2005, 9, 778. (c) Yao, C.-J.; Zhong, Y.-W.;
ACKNOWLEDGMENTS
■
This work is supported by the National Natural Science
Foundation of China (grants 21002104, 91227104, 21271176,
and 212210017), the National Basic Research 973 program of
China (grant 2011CB932301), and the Institute of Chemistry,
Chinese Academy of Sciences (“100 Talent” Program and grant
CMS-PY-201230) for funding support.
REFERENCES
■
(1) (a) Schubert, U. S.; Eschbaumer, C. Angew. Chem., Int. Ed. 2002,
41, 2892. (b) Eryazici, I.; Moorefield, C. N.; Newkome, G. R. Chem.
Rev. 2008, 108, 1834. (c) Medlycott, E. A.; Hanan, G. S. Chem. Soc.
Rev. 2005, 34, 133. (d) Williams, J. A. G. Chem. Soc. Rev. 2009, 38,
1783.
(2) (a) Bruce, M. I. Angew. Chem., Int. Ed. 1977, 16, 73. (b) van der
Boom, M. E.; Milstein, D. Chem. Rev. 2003, 103, 1759. (c) Chi, Y.;
Chou, P.-T. Chem. Soc. Rev. 2010, 39, 638. (d) Albrecht, M. Chem. Rev.
2010, 110, 576.
(3) (a) Djukic, J.-P.; Sortais, J.-B.; Barloy, L.; Pfeffer, M. Eur. J. Inorg.
Chem. 2009, 817. (b) Reveco, P.; Cherry, W. R.; Medley, J.; Garber,
A.; Gale, R. J.; Selbin, J. Inorg. Chem. 1986, 25, 1842. (c) Coudret, C.;
Fraysse, S.; Launay, J.-P. Chem. Commun. 1998, 663. (d) Duprez, V.;
Launay, J.-P.; Gourdon, A. Inorg. Chim. Acta 2003, 343, 395.
(e) Moorlag, C.; Wolf, M. O.; Bohne, C.; Patrick, B. O. J. Am.
Chem. Soc. 2005, 127, 6382. (f) Wadman, S. H.; Lutz, M.; Tooke, D.
M.; Spek, A. L.; Hartl, F.; Havenith, R. W. A.; van Klink, G. P. M.; van
Nie, H.-J.; Abruna, H. D.; Yao, J. J. Am. Chem. Soc. 2011, 133, 20720.
̃
(d) Yao, C.-J.; Yao, J.; Zhong, Y.-W. Inorg. Chem. 2012, 51, 6259.
(10) (a) Yang, W.-W.; Zhong, Y.-W.; Yoshikawa, S.; Shao, J.-Y.;
Masaoka, S.; Sakai, K.; Yao, J.; Haga, M.-a. Inorg. Chem. 2012, 51, 890.
(b) Shao, J.-Y.; Yang, W.-W.; Yao, J.; Zhong, Y.-W. Inorg. Chem. 2012,
51, 4343. (c) Shao, J.-Y.; Yao, J.; Zhong, Y.-W. Organometallics 2012,
31, 4302.
(11) (a) Kober, E. M.; Caspar, J. V.; Sullivan, B. P.; Meyer, T. J. Inorg.
Chem. 1988, 27, 4587. (b) Zhong, Y.-W.; Vila, N.; Henderson, J. C.;
Flores-Torres, S.; Abruna, H. D. Inorg. Chem. 2007, 46, 10470.
̃
(c) Srnec, M.; Chalupsky, J.; Fojta, M.; Zendlova, L.; Havran, L.;
Hocek, M.; Kyvala, M.; Rulisek, L. J. Am. Chem. Soc. 2008, 130, 10947.
(12) (a) Jameson, G. B.; Muster, A.; Robinson, S. D.; Wingfield, J.
N.; Ibers, J. A. Inorg. Chem. 1981, 20, 2448. (b) Wen, T. B.; Cheung, Y.
K.; Yao, J.; Wong, W.-T.; Zhou, Z. Y.; Jia, G. Organometallics 2000, 19,
3803. (c) Gusev, D. G.; Dolgushin, F. M.; Antipin, M. Y.
Organometallics 2001, 20, 1001. (d) Majumder, K.; Peng, S.-M.;
Bhattacharya, S. J. Chem. Soc., Dalton Trans. 2001, 284. (e) Hwang, K.-
C.; Chen, J.-L.; Chi, Y.; Lin, C.-W.; Cheng, Y.-M.; Lee, G.-H.; Chou,
P.-T.; Lin, S.-Y.; Shu, C.-F. Inorg. Chem. 2008, 47, 3307.
Koten, G. Inorg. Chem. 2009, 48, 1887. (g) Jager, M.; Smeigh, A.;
̈
Lombeck, F.; Gorls, H.; Collin, J.-P.; Sauvage, J.-P.; Hammarstrom, L.;
̈
̈
Johannsson, O. Inorg. Chem. 2010, 49, 374. (h) Zhong, Y.-W.; Wu, S.-
H.; Burkhardt, S. E.; Yao, C.-J.; Abruna, H. D. Inorg. Chem. 2011, 50,
517. (i) Yang, W.-W.; Wang, L.; Zhong, Y.-W.; Yao, J. Organometallics
2011, 30, 2236. (j) Wu, S.-H.; Burkhardt, S. E.; Zhong, Y.-W.; Abruna,
̃
̃
H. D. Inorg. Chem. 2012, 51, 13312. (k) Schulze, B.; Escudero, D.;
Friebe, C.; Siebert, R.; Gorls, H.; Sinn, S.; Thomas, M.; Mai, S.; Popp,
J.; Dietzek, B.; Gonzalez, L.; Schubert, U. S. Chem.Eur. J. 2012, 18,
4010. (l) Padhi, S. K.; Tanaka, K. Inorg. Chem. 2011, 50, 10718.
(4) (a) You, Y.; Park, S. Y. Dalton Trans. 2009, 1267. (b) Chen, Z.-q.;
Bian, Z.-q.; Huang, C.-h. Adv. Mater. 2010, 22, 1534. (c) Polson, M.;
Ravaglia, Fracasso, S.; Garavelli, M.; Scandola, F. Inorg. Chem. 2005,
44, 1282. (d) Wilkinson, A. J.; Goeta, A. E.; Foster, C.; Williams, J. A.
G. Inorg. Chem. 2004, 43, 6513.
(5) (a) Lu, W.; Mi, B.-X.; Chan, M. C. W.; Hui, Z.; Che, C.-M.; Zhu,
N.; Lee, S.-T. J. Am. Chem. Soc. 2004, 126, 4958. (b) Shao, P.; Li, Y.;
Yi, J.; Pritchett, T. M.; Sun, W. Inorg. Chem. 2010, 49, 4507.
(c) Hofmann, A.; Dahlenburg, L.; van Eldik, R. Inorg. Chem. 2003, 42,
6528. (d) Cheung, T.-C.; Cheung, K.-K.; Peng, S.-M.; Che, C.-M. J.
Chem. Soc., Dalton Trans. 1996, 1645. (e) Wu, S.-H.; Burkhardt, S. E.;
(13) (a) Ryabov, A. D.; Soukharev, V. S.; Alexandrova, L.; Le
Lagadec, R.; Pfeffer, M. Inorg. Chem. 2003, 42, 6598. (b) Ceron-
Camacho, R.; Morales-Morales, D.; Hernandez, S.; Le Lagadec, R.;
Ryabov, A. D. Inorg. Chem. 2008, 47, 4988. (c) Ceron-Camacho, R.;
Hernanzez, S.; Le Legadec, R. Chem. Commun. 2011, 47, 2823.
(14) (a) Beley, M.; Collin, J.-P.; Sauvage, J.-P. Inorg. Chem. 1993, 32,
4539. (b) Beley, M.; Chodorowski, S.; Collin, J.-P.; Sauvage, J.-P.;
Flamigni, L.; Barigelletti, F. Inorg. Chem. 1994, 33, 2543.
(15) Chung, L.-H.; Chan, S.-C.; Lee, W.-C.; Wong, C.-Y. Inorg. Chem.
2012, 51, 8693.
(16) (a) Haga, M.; Takasugi, T.; Tomie, A.; Ishizuya, M.; Yamada,
T.; Hossain, M. D.; Inoue, M. Dalton Trans. 2003, 2069. (b) Terada,
K.; Kobayashi, K.; Haga, M. Dalton Trans. 2008, 4846. (c) Haga, M.;
Hong, H.-G.; Shiozawa, Y.; Kawata, Y.; Monjushiro, H.; Fukuo, T.;
Arakawa, R. Inorg. Chem. 2000, 39, 4566. (d) Yutaka, T.; Obara, S.;
Ogawa, S.; Nozaki, K.; Ikeda, N.; Ohno, T.; Ishii, Y.; Sakai, K.; Haga,
M. Inorg. Chem. 2005, 44, 4737. (e) Obara, S.; Itabashi, M.; Okuda, F.;
Tamaki, S.; Tanabe, Y.; Ishii, Y.; Nozaki, K.; Haga, M. Inorg. Chem.
2006, 45, 8907. (f) Ruttimann, S.; Bernardinelli, G.; Williams, A. F.
Angew. Chem., Int. Ed. 1993, 32, 392. (g) Carina, R. F.; Williams, A. F.;
Bernardinelli, G. Inorg. Chem. 2001, 40, 1826. (h) Tam, A. Y.-Y.; Lam,
W. H.; Wong, K. M.-C.; Zhu, N.; Yam, V. W.-W. Chem.Eur. J. 2008,
14, 4562. (i) Mathew, I.; Sun, W. Dalton Trans. 2010, 39, 5885.
(j) Wang, K.; Haga, M.; Monjushiro, H.; Akiba, M.; Sasaki, Y. Inorg.
Chem. 2000, 39, 4022. (k) Terazzi, E.; Guenee, L.; Morgantini, P.-Y.;
Bernardinelli, G.; Donnio, B.; Guillon, D.; Piguet, C. Chem.Eur. J.
2007, 13, 1674. (l) Tam, A. Y.-Y.; Tsang, D. P.-K.; Chan, M.-Y.; Zhu,
N.; Yam, V. W.-W. Chem. Commun. 2011, 47, 3383.
Yao, J.; Zhong, Y.-W.; Abruna, H. D. Inorg. Chem. 2011, 50, 3959.
̃
(6) (a) Costa, R. D.; Orti, E.; Bolink, H. J.; Monti, F.; Accorsi, G.;
Armaroli, N. Angew. Chem., Int. Ed. 2012, 51, 8178. (b) Evans, R. C.;
Douglas, P.; Winscom, C. J. Coord. Chem. Rev. 2006, 250, 2093.
(c) Lowry, M. S.; Bernhard, S. Chem.Eur. J. 2006, 12, 7970.
(d) Wong, W.-Y.; Ho, C.-L. J. Mater. Chem. 2009, 19, 4457.
(7) (a) Wadman, S. H.; Kroom, J. M.; Bakker, K.; Lutz, M.; Spek, A.
L.; van Klink, G. P. M.; van Koten, G. Chem. Commun. 2007, 1907.
(b) Bessho, T.; Yoneda, E.; Yum, J.-H.; Guglielmi, M.; Tavernelli, I.;
Imai, H.; Rothlisberger, U.; Nazeeruddin, M. K.; Gratzel, M. J. Am.
Chem. Soc. 2009, 131, 5930. (c) Bomben, P. G.; Koivisto, B. D.;
Berlinguette, C. P. Inorg. Chem. 2010, 49, 4960. (d) Wadman, S. H.;
Kroon, J. M.; Bakker, K.; Havenith, R. W. A.; van Klink, G. P. M.; van
Koten, G. Organometallics 2010, 29, 1569. (e) Robson, K. C. D.;
Koivisto, B. D.; Yella, A.; Sporinova, B.; Nazeeruddin, M. K.;
Baumgartner, T.; Gratzel, M.; Berlinguette, C. P. Inorg. Chem. 2011,
50, 5494. (f) Bomben, P. G.; Gordon, T. J.; Schott, E.; Berlinguette, C.
P. Angew. Chem., Int. Ed. 2011, 50, 10682. (g) Bomben, P. G.; Robson,
K. C. D.; Koivisto, B. D.; Berlinguette, C. P. Coord. Chem. Rev. 2012,
256, 1438.
(17) We use ttpy as a substitute for tpy, because ttpy is much easier
to be synthesized and they have similar electronic properties. Wang,
J.; Hanan, G. S. Synlett 2005, 1251.
H
dx.doi.org/10.1021/ic400385b | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(18) (a) Collin, J.-P.; Guillerez, S.; Sauvage, J.-P. J. Chem. Soc., Chem.
Commun. 1989, 776. (b) Akasaka, T.; Mutai, T.; Otsuki, J.; Araki, K.
Dalton Trans. 2003, 1537.
(19) (a) Yao, C.-J.; Zheng, R.-H.; Shi, Q.; Zhong, Y.-W.; Yao, J.
Chem. Commun. 2012, 48, 5680. (b) Connelly, N. G.; Geiger, W. E.
Chem. Rev. 1996, 96, 877.
(20) Wang, Z.; Turner, E.; Mahoney, V.; Madakuni, S.; Groy, T.; Li,
J. Inorg. Chem. 2010, 49, 11276.
(21) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(22) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.;
Puschmann, H. J. Appl. Crystallogr. 2009, 42, 339.
(23) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A.; Vreven, T., Jr.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.;
Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.;
Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao,
O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J.
B.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev,
O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.;
Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.;
Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman,
J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.;
Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.;
Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen,
W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 09, revision A.2;
Gaussian, Inc.: Wallingford, CT, 2009.
(24) (a) Dunning, T. H.; Hay, P. J. In Modern Theoretical Chemistry;
Schaefer, H. F., Ed.; Plenum: New York, 1976; Vol. 3, p 1. (b) Hay, P.
J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270. (c) Wadt, W. R.; Hay, P.
J. J. Chem. Phys. 1985, 82, 284. (d) Hay, P. J.; Wadt, W. R. J. Chem.
Phys. 1985, 82, 299.
(25) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.;
Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
(26) (a) Klamt, A.; Schuurmann, G. J. Chem. Soc., Perkin Trans. 2
̈
̈
1993, 799. (b) Andzelm, J.; Kolmel, C.; Klamt, A. J. Chem. Phys. 1995,
̈
103, 9312. (c) Barone, V.; Cossi, M. J. Phys. Chem. A 1998, 102, 1995.
(d) Cossi, M.; Rega, N.; Scalmani, G.; Barone, V. J. Comput. Chem.
2003, 24, 669. (e) Takano, Y.; Houk, K. N. J. Chem. Theory Comput.
2005, 1, 70.
I
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