Neutral and cationic NCN pincer platinum(II) complexes with 1,3-bis(benzimidazol-2′-yl)benzene ligands: Synthesis, structures, and their photophysical properties

Article abstract of DOI:10.1021/om400946n

A series of neutral pincer Pt(II) chloride complexes 3-7 were first synthesized via the reaction of 1,3-bis(N-substituted benzimidazol-2′-yl) benzene (bzimb) ligands 2a-e with K₂PtCl₄ in refluxing HOAc. By treatment of complex 3 with KI and aromatic terminal alkynes in methanolic NaOH, the Pt(II) iodide complex 8 and Pt(II) acetylide complexes 9-11 were then obtained. Cationic Pt(II) complexes 12-15 were finally produced by the chloro-substitution reaction of complex 3 with AgOTf and several neutral N-donor ligands. With these new compounds in hand, various characterizations including elemental analysis, NMR, and IR were carried out to investigate their properties. On the basis of the X-ray single-crystal structure analysis of complexes 3-5, 8, 9, and 12, weak intermolecular interactions including π...π stacking and/or hydrogen bonds were found to be responsible for their assembly. After full investigation of the electronic absorption and photoluminescent properties of the Pt(II) complexes 3-15, time-dependent density functional theory (TD-DFT) calculations were carried out to elucidate the origins of the UV-vis absorptions. We were delighted to find that the luminescence quantum yields in degassed CH₂Cl₂ solution were around 0.13 in most cases and the emission lifetimes were in the microsecond range, indicating that these complexes could be used as bright phosphorescent materials with various potential applications in the future.

Full text of DOI:10.1021/om400946n

Article
pubs.acs.org/Organometallics
Neutral and Cationic NCN Pincer Platinum(II) Complexes with 1,3-
Bis(benzimidazol-2′-yl)benzene Ligands: Synthesis, Structures, and
Their Photophysical Properties
Zhao Wang,† Zheming Sun,‡ Xin-Qi Hao,† Jun-Long Niu,† Donghui Wei,† Tao Tu,‡ Jun-Fang Gong,*,†
and Mao-Ping Song†,*
†College of Chemistry and Molecular Engineering, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Zhengzhou
University, Zhengzhou 450001, People’s Republic of China
‡Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433, People’s Republic of China
S
* Supporting Information
ABSTRACT: A series of neutral pincer Pt(II) chloride complexes 3−7 were first synthesized via the reaction of 1,3-bis(N-
substituted benzimidazol-2′-yl) benzene (bzimb) ligands 2a−e with K2PtCl4 in refluxing HOAc. By treatment of complex 3 with
KI and aromatic terminal alkynes in methanolic NaOH, the Pt(II) iodide complex 8 and Pt(II) acetylide complexes 9−11 were
then obtained. Cationic Pt(II) complexes 12−15 were finally produced by the chloro-substitution reaction of complex 3 with
AgOTf and several neutral N-donor ligands. With these new compounds in hand, various characterizations including elemental
analysis, NMR, and IR were carried out to investigate their properties. On the basis of the X-ray single-crystal structure analysis of
complexes 3−5, 8, 9, and 12, weak intermolecular interactions including π···π stacking and/or hydrogen bonds were found to be
responsible for their assembly. After full investigation of the electronic absorption and photoluminescent properties of the Pt(II)
complexes 3−15, time-dependent density functional theory (TD-DFT) calculations were carried out to elucidate the origins of
the UV−vis absorptions. We were delighted to find that the luminescence quantum yields in degassed CH2Cl2 solution were
around 0.13 in most cases and the emission lifetimes were in the microsecond range, indicating that these complexes could be
used as bright phosphorescent materials with various potential applications in the future.
compounds in an OLED, the luminous efficiency of the device
may be potentially improved by a factor of up to 4. On the
other hand, the strong ligand field induced by the cyclo-
metalating ligands in these Pt(II) pincers raised the energies of
d−d excited states and reduced the nonradiative decay
pathways. Consequently, luminescence was promoted. For
example, the Pt(II) complexes with phbpy and dpyb were
emissive in solution at room temperature: in particular, the
[Pt(dpyb)Cl] complexes were among the brightest Pt-based
emitters.5 In contrast, the equivalent nonmetalated Pt(II)
terpyridyl complexes [Pt(tpy)Cl]X (tpy = terpyridine) were
found to be virtually nonluminescent in fluid solution, although
INTRODUCTION
■
Cyclometalated platinum(II) complexes with tridentate pincer
type ligands have aroused considerable interest in recent years,
due to their numerous applications in catalysis, bond activation,
supramolecular chemistry, and materials science. Due to their
intriguing luminescent properties, such complexes have been
widely used in chemosensing, organic light-emitting diodes
(OLEDs), and bioimaging.1 Various types of luminescent
Pt(II) pincer complexes, including CNC with 2,6-diphenylpyr-
idines (dppy),2 CNN with 6-phenyl-2,2′-bipyridines (phbpy),3
and particularly NCN pincers with 1,3-bis(2-pyridyl)benzene
(dpyb),4 have been synthesized for this purpose. On one hand,
the high spin−orbit coupling constant associated with these
complexes enabled them to emit from triplet excited states. By
incorporation of phosphorescent emitters instead of fluorescent
Received: September 23, 2013
Published: March 28, 2014
© 2014 American Chemical Society
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Scheme 1. Synthesis of the Neutral Pincer Pt(II) Halide Complexes 3−8
Scheme 2. Synthesis of the Neutral Pincer Pt(II) Acetylide Complexes 9−11 and the Cationic Complexes 12−15 from the
Chloride Complex 3
they showed strong luminescence in the solid state at room
temperature.6 Furthermore, extensive studies have indicated
that the emission wavelength, lifetime, and quantum efficiency
of the pincer Pt(II) complexes can be fine-tuned by rational
modification of cyclometalating ligands and/or ancillary ligands.
Among the often used ancillary ligands, acetylides were quite
appealing due to their strong ligand field, which could improve
emission efficiencies in solution. Ample literature reports7 have
demonstrated that substitution of the chloride ligand in
cyclometalated pincer Pt(II) complexes such as [Pt(phbpy)Cl]
by acetylides usually causes the emission quantum yields to be
increased.
In addition to systematic studies on complexes containing
dppy, phbpy, and dpyb as well as their extended π-conjugated
analogues,7b,8 research on the other luminescent pincer Pt(II)
complexes including SCS,9 PCP,10 and NCN11 skeletons has
also been carried out. Among them, the major work focused on
NCN pincer complexes containing amine, imine, or various N-
containing heterocycles as N donors. Because of our recent
interest in the synthesis and applications of pincer metal
complexes,12,13 we developed NCN Pt(II) pincers containing
1,3-bis(2′-imidazolinyl)benzene ligands.14 These complexes
were found to be luminescent in solution at room temperature,
although the quantum yields were relatively low (0.0013−
0.0018). However, related cycloplatinated complexes with 2-
arylimidazolines gave higher quantum yields (0.017−0.035).15
Very recently, Yam and coauthors reported the first examples of
luminescent NCN pincer Pt(II) complexes with 1,3-bis(N-
alkylbenzimidazol-2′-yl)benzene (bzimb).16,17 Several Pt(II)
chloride complexes [Pt(bzimb)Cl] and the related [Pt(bzimb)-
(CCR)] complexes exhibited strong green phosphorescence
at room temperature with quantum yields in the range of 0.15−
0.67. Importantly, the emission color could be tuned by
introduction of a substituent at the 5-position of the bzimb
ligands, and the PL quantum efficiency was enhanced by
conversion of chloride to acetylide ligands. Further, some of
these complexes have been utilized as emissive dopants to
fabricate PHOLEDs, giving high current and external quantum
efficiencies (up to 40.3 cd A−1 and 11.8%, respectively). These
results have revealed the potential of this new class of
complexes in lighting technology, display screen technology,
and related areas. Additionally, the bzimb ligands provide facile
functionalization at the nitrogen atom of the benzimidazole
group, in contrast to the well-studied dpyb ligands.
Consequently, following our interests in the development of
new pincer compounds and exploration of their potential
applications, herein we describe the synthesis, characterization,
and absorption and emissive properties of a series of NCN
Pt(II) pincers containing bzimb ligands. With the neutral Pt(II)
halide complexes 3−818 and acetylide complexes 9−11 as well
as the cationic complexes 12−15 in hand (Schemes 1 and 2),
various characterizations were carried out to investigate their
properties. On the basis of the single-crystal X-ray structure
analysis of complexes 3−5, 8, 9, and 12, DFT and TD-DFT
calculations were carried out to elucidate the origins of the
UV−vis absorptions of these pincer Pt(II) complexes.
RESULTS AND DISCUSSION
■
Synthesis and Characterization. The synthesis of the
Pt(II) pincers 3−15 is shown in Schemes 1 and 2 (for the
ligands 2, see Schemes S1 and S2 in the Supporting
Information), respectively. First, 5-hydroxy-1,3-bis-
(benzimidazol-2′-yl)benzene (1) was readily accessible by
heating 5-hydroxyisophthalic acid and 1,2-diaminobenzene in
PPA according to the literature method.19 Then reaction of 1
with excess n-butyl or n-octyl bromide in the presence of NaH
resulted in 5-alkoxy-1,3-bis(N-alkylbenzimidazol-2′-yl)benzene
ligands 2a,b, which further reacted with K2PtCl4 in refluxing
HOAc to afford the corresponding Pt(II) chloride complexes 3
and 4. Similarly, the chloride complexes 5−7 were obtained
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Figure 1. Molecular structures of complexes 4 (left) and 8 (right). Hydrogen atoms have been omitted for clarity.
Figure 2. Molecular structures of complexes 9 (left) and 12 (right). Hydrogen atoms have been omitted for clarity.
a
Table 1. Selected Bond Lengths (Å) and Angles (deg) for Pt(II) Complexes 3−5, 8, 9, and 12
3
4
5
8
9
12
Pt−C
1.914(8)
2.035(6)
2.025(6)
2.379(2)
79.2(3)
1.932(5)
1.927(3)
1.932(8)
2.031(6)
2.049(6)
2.7152(7)
78.7(3)
1.967(5)
1.943(6)
2.031(6)
2.024(6)
2.110(5)
79.5(3)
Pt−N(1)
Pt−N(3)
Pt−X
C−Pt−N(1)
C−Pt−N(3)
N(1)−Pt−X
N(3)−Pt−X
C−Pt−X
N−Pt−N
2.028(4)
2.038(3)
2.030(3)
2.023(4)
2.033(3)
2.029(3)
2.4001(13)
79.37(17)
80.21(17)
100.68(12)
99.79(11)
175.90(13)
159.52(16)
2.3935(9)
79.93(13)
79.45(13)
99.45(8)
2.110(5)
78.71(16)
79.42(16)
101.32(16)
100.55(16)
179.84(19)
158.11(15)
80.6(3)
80.1(3)
80.2(3)
101.12(19)
99.07(19)
179.16(19)
159.7(3)
101.07(19)
100.28(19)
176.1(2)
158.6(3)
98.5(2)
101.18(9)
179.08(10)
159.37(12)
101.8(2)
176.3(3)
159.7(2)
a
Legend: for 3−5, X = Cl; for 8, X = I; for 9, X = C33 (alkynyl); for 12, X = N5 (DMAP).
from platination of substituted-1,3-bis(N-arylbenzimidazol-2′-
yl)benzenes (2c−e), which were prepared by reaction of the
substituted isophthaloyl dichloride with N-arylbenzene-1,2-
diamine.20 With the chloride complex 3 in hand, a series of
neutral and cationic complexes were produced under mild
conditions. Treatment of complex 3 with KI in methanol/
acetone at room temperature gave its iodide analogue 8. To our
delight, transformation of complex 3 to the neutral acetylide
complexes 9−11 was easily achieved by reaction with aromatic
terminal alkynes, including (4-methoxyphenyl)acetylene, phe-
nylacetylene, and (4-nitrophenyl)acetylene, in the presence of
sodium hydroxide in MeOH. In addition, when complex 3 was
treated with AgOTf and a neutral N-donor ligand such as 4-
(dimethylamino)pyridine (DMAP), pyridine, 4-
(trifluoromethyl)pyridine, or benzonitrile, the corresponding
cationic complexes 12−15 were obtained.
The bzimb-H ligands 2a−e and the related NCN pincer
platinum(II) complexes 3−15 were then characterized by
elemental analysis (HRMS for 2a−e) and IR and NMR spectra.
The 1H and 13C NMR spectra of all compounds were
consistent with their C2-symmetrical skeleton (selected 1H
NMR data are given in Table S1 (Supporting Information)). In
comparison with the corresponding ligands 2a−e, the
formation of cyclometalated pincer Pt(II) complexes was
clearly indicated by disappearance of the central aryl proton
1
(ortho to both N donors) signal in the H NMR spectra.
Furthermore, the signals of the other protons on the central
aryl and the 7-position of benzimidazoles were obviously
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shifted upfield. The most prominent shifts were those central
aryl protons in the neutral complexes 5 and 7 (Δδ ≈ 1.1 ppm)
and 7-benzimidazole protons in the cationic complexes 12−14
(Δδ = 0.89−1.56 ppm). The signals of the H-4 protons on
benzimidazole of the neutral complexes 3−11 were shifted
strongly downfield, whereas in the case of the cationic
complexes 12−15 they were shifted upfield. In the 13C NMR
spectra of the ligands 2a−e, the resonances of the carbon atom
on benzimidazolyl CN appeared around 152 ppm and those
of the C-2 atom of central aryl ring were found around 122
ppm (134 ppm for 2d). In the case of pincer complexes 3−15,
the corresponding resonances were shifted downfield. They
were observed in the ranges 160−164 and 148−171 ppm,
respectively, again indicative of N−Pt coordination and C−Pt
bond formation.
well as effective π···π stacking with centroid−centroid distances
of 3.44, 3.83, 3.46, and 3.71 Å. The one-dimensional chains
further connect into a three-dimensional supramolecular
network by intermolecular hydrogen bonds between the Cl
atom and the adjacent C−H group of C4H9N (Cl···H = 2.68 Å)
(Figure S2, Supporting Information). In the crystal structures
of complexes 4 and 5, dimers of 4 and 5 were found due to the
π···π stacking with centroid−centroid distances of 3.49 and
3.55 Å, respectively. Among them, antiparallel head-to-tail
stacking is observed between pairs of complexes and the Cl−
Pt−Pt−Cl torsion angles are 179.9(44) and 179.99(7)°,
respectively (Figures S3 and S4, Supporting Information).
Moreover, the dimer of 5 further assembles into a one-
dimensional supramolecular structure via intermolecular hydro-
gen bonds between the Pt atom and the adjacent C−H group
of CH3O (Pt···H = 3.26 Å). In the case of complex 8, its
mononuclear units assemble into a two-dimensional supra-
molecular structure via intermolecular hydrogen bonds between
the Pt atom and the adjacent C−H group of C4H9N (Pt···H =
3.16 Å) and between the I atom and the adjacent C−H group
of C4H9O (I···H = 3.19 Å) as well as effective π···π stacking
(with centroid−centroid distances of 3.58, 3.67, and 3.76 Å;
Figure S5, Supporting Information). For complex 9, a one-
dimensional supramolecular structure formed by intermolecular
hydrogen bonds between the Pt atom and the adjacent C−H
group of C4H9N (Pt···H = 3.24 Å) and effective π···π stacking
with centroid−centroid distances of 3.59 and 3.68 Å is observed
(Figure S6, Supporting Information). Finally, effective π···π
stacking (with centroid−centroid distances of 3.53 and 3.58 Å)
in complex 12 also constructs the dimeric structure, which is
similar to that of complexes 4 and 5 (Figure S7, Supporting
Information).
X-ray Crystal Structure Determination. The molecular
structures of the neutral Pt(II) complexes 3−5, 8, and 9 and
the cationic complex 12 were determined by single-crystal X-
ray analysis. The structures of 4, 8, 9, and 12 are shown in
Figures 1 and 2 (complexes 3 and 5 are shown in Figure S1
(Supporting Information)). Selected bond lengths and bond
angles are given in Table 1. The main features in the structures
of these six complexes are quite similar. The ligand is
coordinated to the Pt(II) center via two benzimidazolyl N
atoms and the central aryl C atom in a tridentate manner; a
heptacyclic system is thus formed by the central aryl ring and
the two benzimidazole rings as well as two other newly formed
five-membered platinacycles. The heptacyclic rings were
approximately coplanar. For these six complexes, ligands
including chloride, iodide, acetylide, and DMAP occupy the
fourth coordination site of the Pt(II) center. The metal center
in each complex adopts a typical distorted-square-planar
geometry with C−Pt−N and N−Pt−N bond angles around
79 and 159°, respectively, which are in accordance with the
known pincers consisting two fused five-membered-ring
metallacycles and reflect the relative steric strain of the system.
The Pt−N bond distances in the six complexes are ca. 2.023−
2.049 Å, which are comparable with those for the previously
reported pincer Pt-bzimb complexes.16a,c The Pt−C(bzimb)
bond lengths in complexes 4, 5, and 8 are similar (1.927−1.932
Å), while a shorter bond is found in complex 3 (1.914(8) Å)
and a longer bond is found in complex 12 (1.943(6) Å). In
particular, the Pt(II) acetylide complex 9 has the longest Pt−
C(bzimb) bond length (1.967(5) Å), which can be attributed
to the greater trans influence21 of the alkynyl ligand in
comparison to that of the halide or neutral DMAP ligand. On
the other hand, the Pt−C(alkynyl) bond length (2.110(5) Å) in
complex 9 is also found to be longer than that in the known
Pt(II)-bzimpy complex (1.94(11) Å).17c In addition, the Pt−
N(DMAP) bond length (2.110(5) Å) in complex 12 is longer
than the other two Pt−N bond lengths (2.031(6) and 2.024(6)
Å, respectively). The phenomenon can be explained by the
stronger trans influence of the metalated carbanion in
comparison to that of the pyridine or benzimidazole ligand.
After inspection of the packing within the crystals of these
complexes, weak intermolecular interactions including π···π
stacking between the interlayer adjacent bzimb rings and/or
hydrogen bonds were found to support the networks. However,
none of the crystal structures provided evidence for Pt···Pt
interactions. The mononuclear units of complex 3 assemble
into a one-dimensional supramolecular structure via intermo-
lecular hydrogen bonds between the Pt atom and the adjacent
C−H group of C4H9N or C4H9O (Pt···H = 2.85−3.28 Å) as
Absorption Spectroscopy and Theoretical Calcula-
tions. UV−vis spectral data of complexes 3−15 are given in
Table 2. The spectra of representative complexes are shown in
Table 2. Absorption Data in CH2Cl2 Solution (2.5 × 10−5
M) for Complexes 3−15 at Room Temperature
complex
λabs/nm (ε/dm3 mol−1cm−1
)
3
307 (6708), 361 (1299), 395 (1938), 417 (2387), 433 (2937)
307 (9534), 362 (1975), 394 (2865), 416 (3499), 433 (4381)
306 (11080), 360 (2380), 390 (2900), 417 (3730), 434 (4970)
306 (8920), 321 (8450), 358 (2950), 384 (3780), 401 (4670)
309 (7450), 358 (1580), 398 (3610), 421 (4500)
306 (8279), 369 (2152), 412 (2699), 434 (3422)
303 (5564), 386 (1753), 435 (1955)
4
5
6
7
8
9
10
11
12
306 (9985), 395 (3192), 433 (4236)
306 (9360), 396 (7466), 421 (6090)
275 (21470), 299 (22300), 312 (19610), 350 (4860), 381 (6910),
396 (7850), 416 (8680)
13
299 (13920), 312 (15110), 348 (3450), 376 (5100), 394 (6060),
413 (6820)
14
15
300 (11350), 312 (12610), 373 (4180), 392 (4970), 411 (5590)
301 (12770), 314 (14000), 391 (4840), 410 (5400)
Figure 3. All of these complexes display intense absorption
bands in the 228−340 nm region and a relatively low intensity
band at around 348−435 nm. The absorption spectra of the
neutral halide complexes 3−5 and 8 are quite similar (Figures
S8 and S9, Supporting Information). They show a higher
energy band at around 306 nm and a lower energy band at
around 360−434 nm. It is clear that the N-substitution on the
benzimidazole ring and the halide (Cl− or I−) ancillary ligand
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excited states see Figures S12−S17). The relative compositions
of FMOs are collected in Tables S3 and S4 (Supporting
Information). It was found that the LUMOs were very similar
and primarily localized on the bzimb ligand in all cases. For the
Pt(II) halide complexes 3−5 and 8, their HOMOs are mainly
composed by the pincer bzimb ligand (62.3, 63.9, 63.7, and
55.4%, respectively) and there are also minor contributions
from the Pt center (30.4, 29.6, 29.4, and 29.3%, respectively)
and the halide (7.3, 6.5, 6.9, and 15.3%, respectively). However,
the HOMO in the acetylide 9 is formed mainly by the
contribution of the acetylide ligand (67.5%) with minor
contributions of the bzimb ligand (15.1%) and the Pt center
(17.4%). In addition, its HOMO-1 is occupied by the pincer
bzimb ligand, the platinum atom, and the acetylide ligand with
48.8, 25.3, and 25.9% contributions, respectively. For the
cationic complex 12, the HOMO is contributed only by the
pincer bzimb ligand (76.4%) and the platinum atom (22.6%),
whereas the DMAP ligand (1.0%) had little influence.
Calculated selected excited states as well as their assignments
are compiled in Tables S5 and S6 (Supporting Information).
Most of the selected allowed transitions are in agreement with
the experimentally observed absorption maxima. The calculated
lowest energy absorption wavelengths of complexes 3−5 and 8
are in the range 413−417 nm, indicating that the difference
between the complexes is very small. In addition, these
absorptions involve the HOMO → LUMO transitions, which
can be primarily assigned as π → π*(bzimb) 1IL and dπ(Pt) →
Figure 3. UV−vis absorption spectra of complexes 3, 4, 6, 7, 11, and
13 in CH2Cl2 at room temperature.
exhibit negligible influence on the transition energies of the
absorption bands; however, they do have some effect on the
molar extinction coefficients of these bands. In comparison with
complexes 3−5, an obvious blue shift was observed in the
lowest energy absorptions of complexes 6 and 7, which is
attributed to the electron-donating nature of the 4-alkoxy group
relative to hydrogen or fluorine on the central aryl.16c
According to reports on similar bzimb complexes,16a,c the
intense absorption band at around 306 nm in complexes 3−8
can be assigned to an intraligand (IL) π → π* transition of the
bzimb ligand, whereas the lower energy absorptions at 358−
434 nm are ascribed to an IL π → π* transition of the bzimb
ligand, mixed with a metal-to-ligand charge transfer (MLCT)
(dπ(Pt)−π*(bzimb)) transition. For the acetylide complexes
9−11, an intense band at around 304 nm is also observed
(Figure S9, Supporting Information). In addition, complexes 9
and 10 display less intense absorptions at around 390 and 434
nm. For complex 11 with a strong electron-withdrawing nitro
group on the acetylide, intensities of the corresponding
absorptions are obviously enhanced and the absorption at
434 nm is slightly blue shifted to 421 nm. The higher energy
band can be assigned to intraligand (IL) π → π* transitions of
the bzimb and acetylide ligands, whereas the lower energy
absorptions are ascribed to IL π → π* transitions of the bzimb
ligand, mixed with a metal-to-ligand charge transfer (MLCT)
(dπ(Pt)−π*(bzimb)) transition and ligand to ligand charge
transfer (LLCT) (π(CCR3) → π*(bzimb)) character.16a,c
The electronic absorption spectra of the cationic complexes
12−15 exhibit a visible blue shift with a higher energy band at
around 275−330 nm and a lower energy band at around 348−
416 nm in comparison with the bands for complex 3 (Figure
S10, Supporting Information). It was found that the variation of
pyridine with electron-donating or -withdrawing groups or
benzonitrile as ancillary ligand had little influence on the
transition energies of complexes 12−15.
1
π*(bzimb) MLCT transitions, mixed with minor π(Cl/I) →
1
π*(bzimb) LLCT character. For the acetylide complex 9, the
calculated lowest energy singlet absorption wavelength is 409
nm, which is close to those of 3−5 and 8. However, this
absorption is different in nature from those of 3−5 and 8.
Actually, it arises from the HOMO-1 → LUMO excitation,
which can be assigned as an admixture of the [π → π*(bzimb)]
1
1IL state, [dπ(Pt) → π*(bzimb)] MLCT state, and [π(C
1
CC6H4OMe-4) → π*(bzimb)] LLCT state. Furthermore, the
calculated lowest energy absorption wavelength of 12 is 397
nm, and this absorption (associated with HOMO → LUMO)
results from an enhanced contribution from the [π →
1
π*(bzimb)] IL state and a reduced [dπ(Pt) → π*(bzimb)]
1MLCT state in comparison with those of complexes 3−5, 8,
and 9. On the basis of the above calculated results, it is easy to
understand that the lowest energy singlet absorption wave-
lengths of 3−5, 8, and 9 are similar and the corresponding
wavelength of 12 is blue-shifted, which is in line with the
observed trend for the lowest energy absorptions in the UV−vis
absorption spectra of these complexes.
Emission Spectroscopy. The Pt(II) complexes were found
to be luminescent at room temperature in fluid solution, in the
solid state and 77 K glass. The emission data are summarized in
Table 3. Upon excitation at 400−450 nm, a structured emission
band is observed at ca. 529 and 572 nm and a shoulder appears
at ca. 618 nm for the neutral complexes 3−5 and 8−11 in
CH2Cl2 at 298 K. The corresponding emission maxima are
slightly blue shifted to ca. 517, 559, and 604 nm, respectively,
for the cationic complexes 12−15 and neutral complex 7
(Table 3, Figure 4, and Figures S18−S20 (Supporting
Information)). Complex 6 exhibits a structured emission with
λmax peaks at 529 and 561 nm. The large Stokes shifts and
lifetimes in the microsecond range suggest that the emission
originates from a triplet parentage. The vibronically structured
bands reveal spacings of about 1400 cm−1, which are in
accordance with the vibrational modes of the bzimb ligand.16
To better explain the assignments of the absorption spectra,
the same level time-dependent density functional theory (TD-
DFT) calculations were carried out on the basis of the
structures of neutral complexes 3−5, 8, and 9 and cationic
complex 12 (for details see the Supporting Information). The
frontier molecular orbitals (FMOs) involved in the lowest
energy singlet absorptions are depicted in Figure S11
(Supporting Information; for FMOs involved in the main
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Table 3. Emission Data for Complexes 3−15
complex medium (T (K))
λmax/nm (τem/μs)
Φem
a
c
3
4
5
CH2Cl2 (298)
solid (298)
528 (2.8), 571 (3.2), 618 (2.8)
531, 579
0.150
0.145
d
b
b
b
2-MeTHF (77)
522, 565, 614
a
c
CH2Cl2 (298)
529 (1.9), 572 (1.4), 614 (1.2)
537, 577, 619
0.123
0.258
d
solid (298)
2-MeTHF (77)
521, 564, 616
a
c
CH2Cl2 (298)
530 (2.6), 572 (2.5), 621(2.5)
527, 573, 621
0.142
0.182
d
solid (298)
2-MeTHF (77)
521, 564, 615
a
c
c
c
d
6
7
8
CH2Cl2 (298)
529 (7.0), 561 (6.8)
520 (3.4), 561 (3.9), 609 (4.3)
529 (3.2), 571 (3.3), 617 (3.2)
538, 595
0.093
0.118
0.124
0.008
a
CH2Cl2 (298)
a
CH2Cl2 (298)
solid (298)
b
b
b
b
b
b
b
b
2-MeTHF (77)
521, 563, 612
a
c
9
CH2Cl2 (298)
531 (5.3), 573 (4.5), 617 (6.8)
533, 579
0.136
0.053
Figure 4. Normalized emission spectra of complexes 3, 6−9, and 13 in
d
solid (298)
CH2Cl2 at room temperature.
2-MeTHF (77)
522, 566, 613
a
c
c
10
11
12
13
14
15
CH2Cl2 (298)
530 (3.3), 573 (4.3), 618 (3.3)
533, 570
0.150
0.035
found that the emission band was obviously blue-shifted in a
more polar solvent such as DMF in comparison with what was
observed in less polar solvents, including CH2Cl2 (DCM),
CHCl3, THF, and toluene (Figure 5b). The emission maxima
were 475, 517, and 561 nm, respectively. Finally, complexes 3−
5 and 8−15 also displayed structured emission bands in the
solid state at 298 K and in dilute 2-MeTHF solution at 77 K
(Table 3 and Figures S23−S33 (Supporting Information)). In
comparison with emissions in fluid solution at 298 K, the
former emissions were slightly red-shifted (3−10 nm), while
the latter emissions became narrower and slightly blue-shifted
(∼10 nm). Interestingly, complex 4 exhibited a rather high
quantum yield of 0.26 in the solid state, which may be related
to the longer alkyl chains in its structure.
solid (298)
2-MeTHF (77)
520, 565, 617
a
CH2Cl2 (298)
530 (2.7), 574 (2.1), 626 (2.3)
541, 577
solid (298)
2-MeTHF (77)
544
a
c
CH2Cl2 (298)
519 (3.6), 561 (3.6), 607(4.3)
525, 566, 614
0.148
0.005
d
solid (298)
2-MeTHF (77)
511, 553, 601
a
c
CH2Cl2 (298)
517 (5.2), 558 (5.5), 605 (6.0)
522, 561, 605
0.130
0.187
d
solid (298)
2-MeTHF (77)
509, 551, 599
a
c
CH2Cl2 (298)
516 (5.3), 557 (4.3), 603 (4.4)
522, 560, 606
0.122
0.011
d
solid (298)
2-MeTHF (77)
508, 550, 599
a
c
CH2Cl2 (298)
519 (6.1), 559 (4.9), 602 (4.5)
566, 606
0.126
0.083
d
CONCLUSION
solid (298)
■
2-MeTHF (77)
513, 557, 604
A series of luminescent bzimb NCN pincer platinum(II)
complexes have been synthesized and fully characterized. From
the crystal structures of complexes 3−5, 8, 9, and 12, weak
intermolecular interactions including π···π stacking and/or
hydrogen bonds were regarded to support the assembly
networks. The electronic absorption and photoluminescence
properties of the obtained Pt(II) complexes have been
investigated. UV−vis spectra showed the lowest-energy
absorptions in the range 401−435 nm, which were mainly
due to the IL [π → π*(bzimb)]/MLCT[dπ(Pt)−π*(bzimb)]
transitions, as indicated by TD-DFT calculations. In the case of
acetylide complexes, LLCT [π(CCR3) → π*(bzimb)]
transitions were also involved. It was found that the
photoluminescence quantum efficiencies were around 0.13 in
most cases (up to 0.26) with microsecond emission lifetimes,
which were similar to those of the previously reported pincer
Pt(bzimb) complexes applied to OLEDs and further indicated
their utilities as phosphorescent materials with various potential
applications.
a
b
Measured at a concentration of 2.5 × 10−5 M. Measured at a
c
concentration of 2.5 × 10−5 M. The luminescence quantum yield in
CH2Cl2 was measured at ambient temperature with [Ru(bpy)3]2+
d
standard in acetonitrile (Φ = 0.062) as reference. The luminescence
quantum yield in the solid state was measured by integrating sphere at
ambient temperature.
All of the complexes produce quantum yields in the range
0.09−0.15, except for the acetylide complex 11, which contains
a phenylacetylene derivative para-substituted with a NO2 group
and affords a rather low quantum yield (0.035). According to
the previous assignments for the related pincer Pt(II)
complexes with bzimb ligands,16 the emission of the present
complexes most likely originats from the 3IL [π → π*-
(bzimb)]/3MLCT [dπ(Pt) → π*(bzimb)] excited state.
Concentration-dependence studies on complex 3 showed
that the intensity of room-temperature emission was enhanced
with increased concentration in the range of 1.0 × 10−5 to 1.0 ×
10−4 M in CH2Cl2 upon excitation at 433 nm. However, the
emission was significantly restrained when the concentration
was increased to 1.0 × 10−3 M (Figure 5a). The result indicated
that the self-quenching effect probably occurred at higher
concentrations. Similar phenomena were also observed for
complexes 5 and 12 (Figures S21 and S22, Supporting
Information). The influence of different solvents on the
photoluminescence of complex 3 was also investigated. It was
EXPERIMENTAL SECTION
■
General Procedures. Solvents were dried with standard methods
and freshly distilled prior to use if required. 5-Hydroxy-1,3-
bis(benzimidazol-2′-yl)benzene,19 (4-methoxyphenyl)acetylene and
(4-nitrophenyl)acetylene,22 5-butoxyisophthaloyl dichloride,12d,23 and
N-arylbenzene-1,2-diamine24 were prepared according to the literature
methods. All other chemicals were used as purchased.
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Figure 5. (a) Emission spectra of 3 at different concentrations in CH2Cl2. (b) Normalized emission spectra of 3 in different solvents (1.0 × 10−5 M)
at room temperature.
Synthesis of 2a,b. NaH (60% oil dispersion, 0.36 g, 22.5 mmol)
was washed with n-heptane at first, and then it was added to a vial
containing ligand 1 (326 mg, 1 mmol) with 10 mL of DMF. The
mixture was stirred at room temperature for 3 h under nitrogen until
the evolution of gas ceased. At this moment, 10 mmol of alkyl bromide
was added, and the mixture was refluxed for 12 h. After the reaction
mixture was cooled, 10 mL of ethanol was added to quench the
reaction. Then, 20 mL of water was added, this solution was extracted
with ether (20 mL × 3), and the extracts were washed with brine and
then dried over anhydrous Na2SO4. After removal of solvent, the
residue was purified by column chromatography on silica gel to give
the pure product.
Synthesis of 2c−e. A mixture of substituted isophthaloyl
dichloride (1 mmol), N-arylbenzene-1,2-diamine (2.2 mmol), and
triethylamine (450 μL) was stirred in THF (3 mL) under argon at
room temperature for 24 h. Then the mixture was poured into water
and extracted with dichloromethane. After the solvent was removed,
the crude product was dissolved in acetic acid and refluxed for 12 h.
The acetic acid was removed, and the residue was purified by column
chromatography on silica gel to give gray or white solids of ligands
2c−e.
5-Butoxy-1,3-bis(1-(4-methoxyphenyl)-1H-benzo[d]imidazol-2-
yl)benzene (2c). White solid in 21% isolated yield. Mp: 134−136 °C.
1H NMR (400 MHz, CDCl3): δ 7.84 (d, J = 8.0 Hz, 2H,
benzimidazole4 H), 7.36 (t, J = 1.2 Hz, 1H, central Ar2 H), 7.34−
7.30 (m, 2H, benzimidazole6 H), 7.27−7.23 (m, 2H, benzimidazole5
H), 7.18−7.13 (m, 8H, benzimidazole7 H, NAr H and central Ar4,6 H),
6.96 (d, J = 6.8 Hz, 4H, NAr H), 3.83 (s, 6H, OCH3), 3.78 (t, J = 6.6
Hz, 2H, OCH2), 1.66−1.59 (m, 2H, CH2), 1.43−1.34 (m, 2H, CH2),
0.92 (t, J = 7.4 Hz, 3H, CH3). 13C NMR (100 MHz, CDCl3): δ 159.6
(NAr4), 158.8 (central Ar5), 151.9 (CN), 142.9 (benzimidazolyl C-
NC), 137.7 (central Ar1,3), 131.5 (benzimidazolyl C-NAr), 129.4
(NAr1), 128.6 (central Ar4,6), 123.4 and 123.0 (benzimidazole5,6),
122.8 (central Ar2), 120.0 (benzimidazole4), 117.0 and 110.6
(benzimidazole7 and NAr3,5), 115.1 (NAr2,6), 68.0 (OCH2), 55.6
(OCH3), 31.1 (CH2), 19.2 (CH2), 13.8 (CH3). IR (KBr): ν 3419,
2958, 2930, 2867, 2362, 1601, 1512, 1456, 1384, 1292, 1252, 1104,
1029, 871, 833, 744 cm−1. HRMS (positive ESI, m/z): [M + H]+ calcd
for C38H35N4O3 595.2709, found 595.2708.
4,6-Dimethyl-1,3-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)-
benzene (2d). White solid in 70% isolated yield. Mp: 226−228 °C. 1H
NMR (400 MHz, CDCl3): δ 7.87 (d, J = 7.6 Hz, 2H, benzimidazole4
H), 7.45 (s, 1H, central Ar2 H), 7.42−7.27 (m, 12H, NPh H and
benzimidazole5−7 H), 7.10 (dd, J = 8.0, 1.5 Hz, 4H, NPh H), 6.96 (s,
1H, central Ar5 H), 2.07 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3):
δ 152.2 (CN), 143.1 (benzimidazolyl C-NC), 139.2 (central Ar4,6
and NPh1), 136.3 (central Ar1,3), 135.8 (benzimidazolyl C-NPh), 133.6
(central Ar2), 132.4 (central Ar5), 129.6, 128.0, and 126.6 (NPh),
123.4 and 123.0 (benzimidazole5,6), 120.1 (benzimidazole4), 110.5
(benzimidazole7), 19.9 (CH3). IR (KBr): ν 3056, 2962, 2921, 2860,
2813, 1597, 1498, 1449, 1319, 1271, 1192, 1118, 1076, 1033, 975, 896,
831, 745, 697 cm−1. HRMS (positive ESI, m/z): [M + H]+ calcd for
C34H27N4 491.2236, found 491.2234.
5-Butoxy-1,3-bis(1-butyl-1H-benzo[d]imidazol-2-yl)benzene (2a).
1
White solid in 44% isolated yield. Mp: 82−84 °C. H NMR (400
MHz, CDCl3): δ 7.85−7.83 (m, 2H, benzimidazole4 H), 7.56 (t, J =
1.4 Hz, 1H, central Ar2 H), 7.45−7.42 (m, 4H, benzimidazole5,6 H),
7.35−7.30 (m, 4H, benzimidazole7 H and central Ar4,6 H), 4.30 (t, J =
7.6 Hz, 4H, NCH2), 4.12 (t, J = 6.6 Hz, 2H, OCH2), 1.85−1.75 (m,
6H, CH2), 1.57−1.48 (m, 2H, CH2), 1.30−1.21 (m, 4H, CH2), 0.99
(t, J = 7.4 Hz, 3H, CH3), 0.85 (t, J = 7.4 Hz, 6H, CH3). 13C NMR
(100 MHz, CDCl3): δ 159.7 (central Ar5), 152.9 (CN), 143.1
(benzimidazolyl C-NC), 135.7 (central Ar1,3), 132.5 (benzimida-
zolyl C-NC4H9), 123.0 and 122.6 (central Ar4,6 and benzimidazole7),
122.0 (central Ar2), 120.1 (benzimidazole4), 117.1 and 110.4
(benzimidazole5,6), 68.4 (OCH2), 44.7 (NCH2), 31.9 (CH2), 31.3
(CH2), 20.0 (CH2), 19.3 (CH2), 13.9 (CH3), 13.7 (CH3). IR (KBr): ν
3079, 3045, 2956, 2930, 2868, 1596, 1502, 1442, 1416, 1383, 1329,
1285, 1212, 1168, 1067, 1028, 1005, 881, 858, 749, 687 cm−1. HRMS
(positive ESI, m/z): [M + H]+ calcd for C32H39N4O 495.3124, found
495.3121.
1,3-Bis(1-octyl-1H-benzo[d]imidazol-2-yl)-5-octyloxybenzene
(2b). Pale yellow oil in 47% isolated yield. 1H NMR (400 MHz,
CDCl3): δ 7.84−7.82 (m, 2H, benzimidazole4 H), 7.55 (s, 1H, central
Ar2 H), 7.42−7.41 (m, 4H, benzimidazole5,6 H), 7.33−7.28 (m, 4H,
benzimidazole7 H and central Ar4,6 H), 4.27 (t, J = 7.6 Hz, 4H,
NCH2), 4.10 (t, J = 6.6 Hz, 2H, OCH2), 1.87−1.79 (m, 6H, CH2),
1.52−1.44 (m, 2H, CH2), 1.33−1.17 (m, 28H, CH2), 0.89 (t, J = 6.8
Hz, 3H, CH3), 0.82 (t, J = 7.0 Hz, 6H, CH3). 13C NMR (100 MHz,
CDCl3): δ 159.7 (central Ar5), 152.9 (CN), 143.1 (benzimidazolyl
C-NC), 135.7 (central Ar1,3), 132.4 (benzimidazolyl C-NC8H17),
122.9 and 122.5 (central Ar4,6 and benzimidazole7), 121.9 (central
Ar2), 120.1 (benzimidazole4), 117.0 and 110.3 (benzimidazole5,6), 68.7
(OCH2), 44.9 (NCH2), 31.9 (CH2), 31.7 (CH2), 29.9 (CH2), 29.7
(CH2), 29.4 (CH2), 29.3 (CH2), 29.2 (CH2), 29.1 (CH2), 26.7 (CH2),
26.0 (CH2), 22.7 (CH2), 22.6 (CH2), 14.13 (CH3), 14.06 (CH3). IR
(KBr): ν 3060, 2925, 2854, 1601, 1458, 1390, 1327, 1284, 1224, 1186,
1049, 1008, 883, 858, 750, 692 cm−1. HRMS (positive ESI, m/z): [M
+ H]+ calcd for C44H63N4O 663.5002, found 663.5003.
5-Fluoro-1,3-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene
1
(2e). White solid in 57% isolated yield. Mp: 181−183 °C. H NMR
(400 MHz, CDCl3): δ 7.86 (d, J = 8.0 Hz, 2H, benzimidazole4 H),
7.60 (s, 1H, central Ar2 H), 7.56−7.43 (m, 6H, NPh H), 7.35 (t, J =
7.6 Hz, 2H) and 7.31−7.28 (m, 4H, benzimidazole5,6 H and central
Ar4,6 H), 7.21 (d, J = 7.2 Hz, 6H, NPh H and benzimidazole7 H). 13
C
NMR (100 MHz, CDCl3): δ 162.0 (d, JC−F = 245.5 Hz, central Ar5),
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150.3 (CN), 142.9 (benzimidazolyl C-NC), 137.3 (NPh1), 136.4
(benzimidazolyl C-NPh), 132.4 (d, JC−F = 8.8 Hz, central Ar1,3), 130.1,
129.1, and 127.4 (NPh), 126.2 (d, JC−F = 2.7 Hz, central Ar2), 123.9
for C38H33ClN4O3Pt (824.23): C, 55.37; H, 4.04; N, 6.80. Found: C,
55.07; H, 3.94; N, 6.61.
(3,5-Dimethyl-2,6-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)-
phenyl)platinum(II) Chloride (6). Yellow solid in 33% yield. Mp: >280
°C. 1H NMR (400 MHz, CDCl3): δ 9.28 (d, J = 8.4 Hz, 2H,
benzimidazole4 H), 7.62−7.56 (m, 6H, NPh H), 7.49 (dd, J = 7.8, 1.8
Hz, 4H, NPh H), 7.45 (dd, J = 8.2, 1.0 Hz, 2H, benzimidazole6 H),
7.29 (dd, J = 8.2, 1.0 Hz, 2H, benzimidazole5 H), 7.18 (d, J = 8.0 Hz,
2H, benzimidazole7 H), 6.43 (s, 1H, central Ar4 H), 1.49 (s, 6H, CH3).
13C NMR (100 MHz, CDCl3): δ 164.5 (CN), 164.4 (central Ar1),
and 123.3 (benzimidazole5,6), 120.2 (benzimidazole4), 117.4 (d, JC−F
=
23.7 Hz, central Ar4,6), 110.7 (benzimidazole7). 19F NMR (400 MHz,
CDCl3): δ −111.5. IR (KBr): ν 3052, 2925, 2855, 1595, 1498, 1452,
1420, 1376, 1331, 1284, 1207, 1152, 1104, 1076, 1007, 943, 869, 746,
691 cm−1. HRMS (positive ESI, m/z): [M + H]+ calcd for C32H22FN4
481.1828, found 481.1824.
Synthesis of the Pincer Pt(II) Chloride Complexes 3−7. A
mixture of 2a−e (0.5 mmol) and K2PtCl4 (250 mg, 0.6 mmol) in
glacial acetic acid (50 mL) was refluxed for 48 h. After it was cooled to
room temperature, the reaction mixture was filtered through Celite,
and the solvent was removed under reduced pressure. Then the
residue was purified by preparative TLC on silica gel plates with
CH2Cl2 as eluent to give complexes 3−7 as orange or yellow solids.
(4-Butoxy-2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)phenyl)-
platinum(II) Chloride (3). Orange solid in 77% isolated yield. Mp:
272−274 °C. 1H NMR (400 MHz, CDCl3): δ 8.82 (d, J = 8.0 Hz, 2H,
benzimidazole4 H), 7.23 (t, J = 7.6 Hz, 2H, benzimidazole6 H), 7.10 (t,
J = 7.6 Hz, 2H, benzimidazole5 H), 6.96 (d, J = 8.0 Hz, 2H,
benzimidazole7 H), 6.72 (s, 2H, central Ar3,5 H), 4.43 (t, J = 7.4 Hz,
4H, NCH2), 3.65 (t, J = 6.0 Hz, 2H, OCH2), 1.80−1.72 (m, 4H,
CH2), 1.40−1.30 (m, 8H, CH2), 0.90 (t, 9H, J = 7.4 Hz, CH3). 13C
NMR (100 MHz, CDCl3): δ 160.9 (CN), 155.4 (central Ar4), 151.5
(central Ar1), 141.0 (benzimidazolyl C-NC), 133.9 (central Ar2,6),
131.2 (benzimidazolyl C-NC4H9), 123.9 (benzimidazole6), 122.9
(benzimidazole5), 118.9 (benzimidazole4), 110.6 (central Ar3,5),
109.2 (benzimidazole7), 68.3 (OCH2), 44.8 (NCH2), 31.9 (CH2),
31.3 (CH2), 20.3 (CH2), 19.2 (CH2), 14.0 (CH3), 13.8 (CH3). IR
(KBr): ν 2958, 2928, 2868, 1602, 1517, 1456, 1400, 1293, 1267, 1210,
1163, 1113, 1064, 1014, 750 cm−1. Anal. Calcd for C32H37ClN4OPt
(724.20): C, 53.07; H, 5.15; N, 7.74. Found: C, 53.19; H, 5.22; N,
7.65.
(2,6-Bis(1-octyl-1H-benzo[d]imidazol-2-yl)-4-(octyloxy)phenyl)-
platinum(II) Chloride (4). Orange solid in 78% isolated yield. Mp:
208−210 °C. 1H NMR (400 MHz, CDCl3): δ 8.86 (d, J = 8.0 Hz, 2H,
benzimidazole4 H), 7.27 (t, J = 7.6 Hz, 2H, benzimidazole6 H), 7.15 (t,
J = 7.6 Hz, 2H, benzimidazole5 H), 7.01 (d, J = 8.0 Hz, 2H,
benzimidazole7 H), 6.78 (s, 2H, central Ar3,5 H), 4.46 (t, J = 7.4 Hz,
4H, NCH2), 3.71 (t, J = 5.8 Hz, 2H, OCH2), 1.83−1.80 (m, 4H,
CH2), 1.45−1.23 (m, 32H, CH2), 0.93 (t, J = 6.8 Hz, 3H, CH3), 0.87
(t, J = 6.4 Hz, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 160.9 (C
N), 155.5 (central Ar4), 151.7 (central Ar1), 141.2 (benzimidazolyl C-
NC), 134.0 (central Ar2,6), 131.4 (benzimidazolyl C-NC8H17),
124.0 (benzimidazole6), 123.0 (benzimidazole5), 119.0 (benzimida-
zole4), 110.7 (central Ar3,5), 109.2 (benzimidazole7), 68.7 (OCH2),
45.0 (NCH2), 32.1 (CH2), 31.9 (CH2), 30.0 (CH2), 29.7 (CH2), 29.5
(CH2), 29.43 (CH2), 29.39 (CH2), 29.32 (CH2), 27.1 (CH2), 26.2
(CH2), 22.9 (CH2), 22.7 (CH2), 14.3 (CH3), 14.2 (CH3). IR (KBr): ν
3059, 3022, 2925, 2853, 1599, 1515, 1457, 1378, 1292, 1267, 1160,
1069, 1013, 747 cm−1. Anal. Calcd for C44H61ClN4OPt (892.52): C,
59.21; H, 6.89; N, 6.28. Found: C, 59.41; H, 6.91; N, 6.11.
141.5 (benzimidazolyl C-NC), 137.8 (benzimidazolyl C-NPh),
136.8 (central Ar3,5), 136.1 (central Ar2,6), 130.5 (central Ar4), 130.3,
129.7, 129.5, and 127.7 (NPh), 125.3 (benzimidazole6), 124.1
(benzimidazole5), 119.8 (benzimidazole4), 110.8 (benzimidazole7),
21.7 (CH3). IR (KBr): ν 3049, 2968, 2855, 1629, 1594, 1568, 1497,
1443, 1416, 1388, 1342, 1305, 1269, 1231, 1202, 1154, 1114, 1075,
1015, 925, 849, 737, 700 cm−1. Anal. Calcd for C34H25ClN4Pt·CH2Cl2
(805.05): C, 52.22; H, 3.38; N, 6.96; Found: C, 52.07; H, 3.34; N,
6.64.
(4-Fluoro-2,6-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)-
platinum(II) Chloride (7). Yellow solid in 23% yield. Mp: >280 °C. 1H
NMR (400 MHz, CDCl3): δ 9.15 (d, J = 8.0 Hz, 2H, benzimidazole4
H), 7.73−7.71 (m, 6H, NPh H), 7.57−7.55 (m, 4H, NPh H), 7.52−
7.48 (m, 2H, benzimidazole6 H), 7.34 (t, J = 7.6 Hz, 2H,
benzimidazole5 H), 7.12 (d, J = 8.4 Hz, 2H, benzimidazole7 H),
6.15 (d, J = 10.0 Hz, 2H, central Ar3,5). 13C NMR (100 MHz, CDCl3):
δ 141.3 (benzimidazolyl C-NC), 135.8 (central Ar2,6), 134.1
(NPh1), 131.0, 130.7, and 127.9 (NPh), 125.6 (benzimidazole6),
124.7 (benzimidazole5), 119.8 (benzimidazole4), 111.3 (central Ar3,5),
110.5 (benzimidazole7). 19F NMR (400 MHz, CDCl3): δ −118.1. IR
(KBr): ν 3062, 2924, 2854, 1593, 1508, 1450, 1373, 1296, 1225, 1185,
1107, 1075, 1007, 941, 856, 745, 698 cm−1.
Synthesis of the Pincer Pt(II) Iodide Complex 8. A mixture of
chloroplatinum complex 3 (0.2 mmol) and potassium iodide (332 mg,
2 mmol) were stirred in methanol/acetone (1/1 v/v, 20 mL) at room
temperature for 12 h. The reaction mixture was filtered through Celite,
and solvent was removed under reduced pressure. Then the residue
was purified by preparative TLC on silica gel plates with dichloro-
methane as eluent to give the iodoplatinum complex 8 as orange solid.
(4-Butoxy-2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)phenyl)-
platinum(II) Iodide (8). Orange solid in 82% isolated yield. Mp: 295−
1
297 °C. H NMR (400 MHz, CDCl3): δ 9.45 (d, J = 8.4 Hz, 2H,
benzimidazole4 H), 7.28 (t, J = 7.2 Hz, 2H, benzimidazole6 H), 7.16 (t,
J = 7.2 Hz, 2H, benzimidazole5 H), 6.98 (d, J = 8.0 Hz, 2H,
benzimidazole7 H), 6.85 (s, 2H, central Ar3,5 H), 4.48 (t, J = 7.6 Hz,
4H, NCH2), 3.81 (t, J = 6.4 Hz, 2H, OCH2), 1.83−1.76 (m, 4H,
CH2), 1.45−1.36 (m, 8H, CH2), 0.96−0.91 (m, 9H, CH3). 13C NMR
(100 MHz, CDCl3): δ 161.5 (CN), 155.8 (central Ar4), 152.9
(central Ar1), 142.1 (benzimidazolyl C-NC), 134.1 (central Ar2,6),
131.1 (benzimidazolyl C-NC4H9), 123.8 (benzimidazole6), 123.3
(benzimidazole5), 121.7 (benzimidazole4), 110.9 (central Ar3,5),
109.2 (benzimidazole7), 68.6 (OCH2), 44.8 (NCH2), 32.0 (CH2),
31.4 (CH2), 20.3 (CH2), 19.3 (CH2), 14.1 (CH3), 13.9 (CH3). IR
(KBr): ν 3067, 2958, 2930, 2867, 1603, 1522, 1447, 1382, 1293, 1266,
1211, 1163, 1114, 1063, 1018, 935, 894, 840, 738 cm−1. Anal. Calcd
for C32H37IN4OPt (815.65): C, 47.12; H, 4.57; N, 6.87. Found: C,
47.10; H, 4.51; N, 6.61.
(4-Butoxy-2,6-bis(1-(4-methoxyphenyl)-1H-benzo[d]imidazol-2-
yl)phenyl)platinum(II) Chloride (5). Orange solid in 78% isolated
yield. Mp: 280 °C dec. 1H NMR (400 MHz, CDCl3): δ 9.01 (d, J = 8.4
Hz, 2H, benzimidazole4 H), 7.50 (d, J = 8.8 Hz, 4H, NAr H), 7.40 (t, J
= 7.8 Hz, 2H, benzimidazole6 H), 7.26 (t, J = 7.6 Hz, 2H,
benzimidazole5 H), 7.15 (d, J = 8.8 Hz, 4H, NAr H), 7.06 (d, J =
8.0 Hz, 2H, benzimidazole7 H), 6.00 (s, 2H, central Ar3,5 H), 3.95 (s,
6H, OCH3), 3.26 (t, J = 7.0 Hz, 2H, OCH2), 1.44−1.37 (m, 2H,
CH2), 1.25−1.16 (m, 2H, CH2), 0.85 (t, J = 7.4 Hz, 3H, CH3). 13C
NMR (100 MHz, CDCl3): δ 161.4 (CN), 161.0 (NAr4), 154.8
(central Ar4), 152.9 (central Ar1), 141.3 (benzimidazolyl C-NC),
136.0 (central Ar2,6), 131.9 (benzimidazolyl C-NAr), 129.3 (NAr3,5),
126.8 (NAr1), 125.0 (benzimidazole6), 124.0 (benzimidazole5), 119.4
(benzimidazole4), 115.4 (NAr2,6), 111.4 (central Ar3,5), 110.3
(benzimidazole7), 68.3 (OCH2), 55.9 (OCH3), 30.9 and 19.0
(CH2), 13.8 (CH3). IR (KBr): ν 3412, 3060, 2932, 1605, 1514,
1449, 1298, 1252, 1192, 1173, 1113, 1028, 840, 750 cm−1. Anal. Calcd
Synthesis of the Pt(II) Acetylide Complexes 9−11. A mixture
of arylacetylene (0.22 mmol) and sodium hydroxide (0.22 mmol) in
methanol was stirred at room temperature for 30 min. Complex 3
(0.20 mmol) was added to the reaction mixture, and this mixture was
stirred for an additional 12 h at room temperature. The crude product
was filtered and washed well with methanol and diethyl ether. Then,
the pure orange-red complexes 9−11 were obtained by diffusion of n-
hexane into dichloromethane solutions of the products.
(4-Butoxy-2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)phenyl)((4-
methoxyphenyl)ethynyl)platinum (9). Orange solid in 69% isolated
yield. Mp: 273−274 °C dec. 1H NMR (400 MHz, CDCl3): δ 8.96 (d, J
= 8.0 Hz, 2H, benzimidazole4 H), 7.62 (d, J = 8.4 Hz, 2H, Ar2,6 H),
7.27 (t, J = 7.4 Hz, 2H, benzimidazole6 H), 7.14 (t, J = 7.4 Hz, 2H,
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benzimidazole5 H), 7.00 (d, J = 8.0 Hz, 2H, benzimidazole7 H), 6.96
(d, J = 8.8, Hz, 2H, Ar3,5 H), 6.90 (s, 2H, central Ar3,5 H), 4.51 (t, J =
7.4 Hz, 4H, NCH2), 3.89 (s, 3H, OCH3), 3.65 (t, J = 6.4 Hz, 2H,
OCH2), 1.85−1.78 (m, 4H, CH2), 1.42−1.34 (m, 6H, CH2), 1.29−
1.23 (m, 2H, CH2), 0.94−0.87 (m, 9H, CH3). 13C NMR (100 MHz,
CDCl3): δ 171.1 (central Ar1), 163.7 (CN), 157.2 (Ar4), 155.8
(central Ar4), 141.6 (benzimidazolyl C-NC), 133.9 (central Ar2,6),
133.1 (benzimidazolyl C-NC4H9), 132.5 (Ar2,6), 123.6 (benzimida-
zole6), 122.8 (benzimidazole5), 122.6 (Pt−C), 119.5 (benzimida-
zole4), 119.0 (Ar1), 114.2 (C−Ar), 113.8 (Ar3,5), 110.8 (central
Ar3,5), 109.1 (benzimidazole7), 68.5 (OCH2), 55.5 (OCH3), 44.8
(NCH2), 32.0 (CH2), 31.4 (CH2), 20.3 (CH2), 19.2 (CH2), 14.0
(CH3), 13.8 (CH3). IR (KBr): ν 3058, 2958, 2930, 2869, 2081, 1595,
1501, 1457, 1438, 1262, 1235, 1206, 1164, 1100, 1074, 1027, 826, 801,
751 cm−1. Anal. Calcd for C41H44N4O2Pt·0.25CH2Cl2 (841.13): C,
58.90; H, 5.33; N, 6.66. Found: C, 58.89; H, 5.46; N, 6.66.
(4-Butoxy-2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)phenyl)-
(phenylethynyl)platinum (10). Orange solid in 67% isolated yield.
Mp: 293−295 °C dec. 1H NMR (400 MHz, CDCl3): δ 8.94 (d, J = 8.4
Hz, 2H, benzimidazole4 H), 7.69 (d, J = 6.8 Hz, 2H, Ph2,6 H), 7.40 (t, J
= 7.6 Hz, 2H, benzimidazole6 H), 7.31−7.21(m, 3H, Ph3−5 H), 7.16 (t,
J = 7.4 Hz, 2H, benzimidazole5 H), 7.02 (d, J = 8.0 Hz, 2H,
benzimidazole7 H), 6.92 (s, 2H, central Ar3,5 H), 4.52 (t, J = 7.4 Hz,
4H, NCH2), 3.66 (t, J = 6.4 Hz, 2H, OCH2), 1.87−1.79 (m, 4H,
CH2), 1.43−1.34 (m, 6H, CH2), 1.30−1.24 (m, 2H, CH2), 0.94−0.87
(m, 9H, CH3). 13C NMR (100 MHz, CDCl3): δ 171.1 (central Ar1),
163.7 (CN), 156.0 (central Ar4), 141.6 (benzimidazolyl C-NC),
133.9 (central Ar2,6), 133.2 (benzimidazolyl C-NC4H9), 131.5 (Ph2),
129.8 (Ph1), 128.1 (benzimidazole6), 125.5 (Pt−C), 124.7 and
123.7 (Ph3−5), 122.9 (benzimidazole5), 119.5 (benzimidazole4), 115.0
(C-Ph), 110.8 (central Ar3,5), 109.1 (benzimidazole7), 68.5
(OCH2), 44.8 (NCH2), 32.1 (CH2), 31.4 (CH2), 20.3 (CH2), 19.3
(CH2), 14.1 (CH3), 13.9 (CH3). IR (KBr): ν 2958, 2926, 2867, 2084,
1632, 1599, 1514, 1451, 1399, 1294, 1209, 1163, 1018, 835, 750 cm−1.
Anal. Calcd for C40H42N4OPt·0.5CH2Cl2 (832.34): C, 58.44; H, 5.21;
N, 6.73. Found: C, 58.37; H, 5.42; N, 7.17.
(4-Butoxy-2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)phenyl)((4-
nitrophenyl)ethynyl)platinum (11). Orange solid in 77% isolated
yield. Mp: 297 °C dec. 1H NMR (400 MHz, CDCl3): δ 8.71 (d, J = 8.0
Hz, 2H, benzimidazole4 H), 8.27 (d, J = 8.8 Hz, 2H, Ar3,5 H), 7.71 (d,
J = 8.8 Hz, 2H, Ar2,6 H), 7.29 (t, J = 7.2 Hz, 2H, benzimidazole6 H),
7.19 (t, J = 7.4 Hz, 2H, benzimidazole5 H), 7.05 (d, J = 8.0 Hz, 2H,
benzimidazole7 H), 6.92 (s, 2H, central Ar3,5 H), 4.48 (t, J = 7.4 Hz,
4H, NCH2), 3.71 (t, J = 6.6 Hz, 2H, OCH2), 1.86−1.82 (m, 4H,
CH2), 1.46−1.39 (m, 6H, CH2), 1.33−1.28 (m, 2H, CH2), 0.96−0.88
(m, 9H, CH3). 13C NMR (100 MHz, CDCl3): δ 170.1 (central Ar1),
163.5 (CN), 156.3 (central Ar4), 144.5 (Ar4), 141.4 (benzimidazolyl
C-NC), 136.8 (Ar1), 133.9 (central Ar2,6), 133.2 (benzimidazolyl C-
NC4H9), 131.7 (Ar2,6), 126.4 (Pt−C), 123.95 (Ar3,5), 123.88
(benzimidazole6), 123.2 (benzimidazole5), 118.9 (benzimidazole4),
115.1 (C−Ar), 110.8 (central Ar3,5), 109.3 (benzimidazole7), 68.5
(OCH2), 44.9 (NCH2), 32.0 (CH2), 31.4 (CH2), 20.3 (CH2), 19.3
(CH2), 14.0 (CH3), 13.8 (CH3). IR (KBr): ν 3062, 2958, 2932, 2870,
2076, 1584, 1507, 1457, 1441, 1382, 1331, 1293, 1210, 1166, 1107,
853, 751 cm−1. Anal. Calcd for C40H41N5O3Pt (834.87): C, 57.55; H,
4.95; N, 8.39. Found: C, 57.70; H, 5.09; N, 8.12.
Synthesis of the Cationic Pt(II) Complexes 12−15. In a flask
covered with foil to avoid light, the neutral chloroplatinum 3 (0.3
mmol) and silver trifluoromethanesulfonate (154 mg, 0.6 mmol) were
stirred in the presence of the N-donor ligand (1 equiv) in CH2Cl2 (10
mL) at room temperature for 24 h. After removal of AgCl by repeated
filtration through Celite with CH2Cl2 as eluent and evaporation of
CH2Cl2, the residue was purified by recrystallization from CH2Cl2/n-
hexane to give 12−15 as yellow solids.
H), 6.46 (d, J = 7.2 Hz, 2H, benzimidazole7 H), 6.14 (d, J = 8.0 Hz,
2H, pyridine3,5 H), 4.50 (t, J = 7.2 Hz, 4H, NCH2), 4.08 (t, J = 6.4 Hz,
2H, OCH2), 3.18 (s, 6H, N(CH3)2), 1.95−1.83 (m, 6H, CH2), 1.63−
1.54 (m, 2H, CH2), 1.49−1.40 (m, 4H, CH2), 1.04 (t, J = 7.4 Hz, 3H,
CH3), 0.95 (t, J = 7.4 Hz, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ
161.4 (CN), 157.4 (central Ar4), 155.0 (pyridine4), 152.3 (central
Ar1), 151.1 (pyridine2,6), 139.3 (benzimidazolyl C-NC), 134.2
(central Ar2,6), 133.0 (benzimidazolyl C-NC4H9), 125.5 (benzimida-
zole5), 124.4 (benzimidazole6), 115.0 (pyridine3,5), 111.5 (benzimida-
zole4), 111.3 (central Ar3,5), 108.2 (benzimidazole7), 69.3 (OCH2),
45.1 (NCH2), 39.7 (N(CH3)2), 32.2 (CH2), 31.5 (CH2), 20.3 (CH2),
19.5 (CH2), 14.1 (CH3), 13.9 (CH3). 19F NMR (400 MHz, CDCl3): δ
−78.0. IR (KBr): ν 3445, 3112, 2956, 2870, 1619, 1524, 1447, 1391,
1266, 1219, 1152, 1068, 1027, 816, 751, 636, 518 cm−1. Anal. Calcd
for C40H47F3N6O4PtS (959.98): C, 50.05; H, 4.93; N, 8.75. Found: C,
49.90; H, 5.13; N, 8.63.
(4-Butoxy-2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)phenyl)-
(pyridine)platinum(II) Triflate (13). Yellow solid in 85% isolated yield.
Mp: 266−267 °C dec. 1H NMR (400 MHz, CDCl3) δ 9.09 (d, J = 4.4
Hz, 2H, pyridine2,6 H), 8.35 (t, J = 7.8 Hz, 1H, pyridine4 H), 7.76 (t, J
= 6.6 Hz, 2H, pyridine3,5 H), 7.54 (d, J = 8.4 Hz, 2H, benzimidazole4
H), 7.35 (t, J = 7.4, 2H, benzimidazole6 H), 7.15 (s, 2H, central Ar3,5
H), 7.10 (t, J = 7.8 Hz, 2H, benzimidazole5 H), 5.82 (d, J = 8.4 Hz,
2H, benzimidazole7 H), 4.56 (t, J = 7.0 Hz, 4H, NCH2), 4.10 (t, J = 6.4
Hz, 2H, OCH2), 1.98−1.91 (m, 4H, CH2), 1.90−1.83 (m 2H, CH2),
1.63−1.53 (m, 2H, CH2), 1.52−1.42 (m, 4H, CH2), 1.04 (t, J = 7.4
Hz, 3H, CH3), 0.97 (t, J = 7.4 Hz, 6H, CH3). 13C NMR (100 MHz,
CDCl3): δ 161.1 (CN), 157.8 (central Ar4), 152.6 (pyridine2,6),
150.2 (central Ar1), 141.1 (pyridine4), 139.1 (benzimidazolyl C-N
C), 134.1 (central Ar2,6), 133.0 (benzimidazolyl C-NC4H9), 127.4
(pyridine3,5), 125.5 (benzimidazole5), 124.5 (benzimidazole6), 114.3
(benzimidazole7), 111.7 (benzimidazole4), 111.5 (central Ar3,5), 69.3
(OCH2), 45.1 (NCH2), 32.2 (CH2), 31.4 (CH2), 20.2 (CH2), 19.4
(CH2), 14.0 (CH3), 13.9 (CH3). 19F NMR (400 MHz, CDCl3): δ
−78.0. IR (KBr): ν 3447, 3104, 2960, 2869, 1599, 1519, 1449, 1398,
1266, 1216, 1157, 1064, 1027, 758, 700, 635 cm−1. Anal. Calcd for
C38H42F3N5O4PtS·H2O (934.93): C, 48.82; H, 4.74; N, 7.49. Found:
C, 48.96; H, 4.63; N, 7.39.
(4-Butoxy-2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)phenyl)(4-
(trifluoromethyl)pyridine)platinum(II) Triflate (14). Yellow solid in
61% isolated yield, Mp: 266−267 °C dec. 1H NMR (400 MHz,
CDCl3) δ 9.56 (d, J = 6.0 Hz, 2H, pyridine2,6 H), 8.15 (d, J = 6.0 Hz,
2H, pyridine3,5 H), 7.53 (d, J = 8.4 Hz, 2H, benzimidazole4 H), 7.34 (t,
J = 7.8 Hz, 2H, benzimidazole6 H), 7.21 (s, 2H, central Ar3,5 H), 7.10
(t, J = 7.8 Hz, 2H, benzimidazole5 H), 5.79 (d, J = 8.0 Hz, 2H,
benzimidazole7 H), 4.61 (t, J = 7.2 Hz, 4H, NCH2), 4.10 (t, J = 6.4 Hz,
2H, OCH2), 2.02−1.95 (m, 4H, CH2), 1.88−1.81 (m, 2H, CH2),
1.60−1.45 (m, 6H, CH2), 1.04−0.97 (m, 9H, CH3). 13C NMR (100
MHz, CDCl3): δ 160.9 (CN), 158.1 (central Ar4), 154.4
(pyridine2,6), 148.8 (central Ar1), 141.8 (pyridine4), 139.1 (benzimi-
dazolyl C-NC), 134.1 (central Ar2,6), 133.0 (benzimidazolyl C-
NC4H9), 125.5 (benzimidazole5), 124.5 (benzimidazole6), 123.3
(pyridine3,5), 114.0 (benzimidazole7), 111.8 (benzimidazole4), 111.6
(central Ar3,5), 69.3 (OCH2), 45.2 (NCH2), 32.2 (CH2), 31.4 (CH2),
20.2 (CH2), 19.4 (CH2), 14.0 (CH3), 13.8 (CH3). 19F NMR (400
MHz, CDCl3): δ −64.8, −78.1. IR (KBr): ν 3443, 3101, 2961, 2871,
1600, 1521, 1452, 1325, 1266, 1216, 1151, 1029, 844, 750, 637 cm−1.
Anal. Calcd for C39H41F6N5O4PtS (984.91): C, 47.56; H, 4.20; N,
7.11. Found: C, 47.48; H, 4.18; N, 6.86.
(4-Butoxy-2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)phenyl)-
(benzonitrile)platinum(II) Triflate (15). Yellow solid in 92% yield, Mp:
1
177−178 °C dec. H NMR (400 MHz, CDCl3) δ 7.83−7.73 (m, 5H,
Ph H), 7.37 (t, J = 7.2 Hz, 2H, benzimidazole6 H), 7.30−7.24 (m, 4H,
benzimidazole4,5 H), 7.14 (d, J = 8.0 Hz, 2H, benzimidazole7 H), 6.88
(s, 2H, central Ar3,5 H), 4.28 (t, J = 6.6 Hz, 4H, NCH2), 3.94 (t, J = 6.0
Hz, 2H, OCH2), 1.82−1.73 (m, 6H, CH2), 1.56−1.51 (m, 2H, CH2),
1.39−1.33 (m, 4H, CH2), 1.03 (t, J = 7.4 Hz, 3H, CH3), 0.88 (t, J = 7.2
Hz, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 159.7 (CN), 157.8
(central Ar4), 148.4 (central Ar1), 139.0 (benzimidazolyl C-NC),
135.6 (Ph4), 133.5 (central Ar2,6), 132.6 (benzimidazolyl C-NC4H9),
(4-Butoxy-2,6-bis(1-butyl-1H-benzo[d]imidazol-2-yl)phenyl)(4-
(dimethylamino)pyridine)platinum(II) Triflate (12). Yellow solid in
76% isolated yield. Mp: 249−250 °C dec. 1H NMR (400 MHz,
CDCl3) δ 8.40 (d, J = 6.8 Hz, 2H, pyridine2,6 H), 7.54 (d, J = 8.4 Hz,
2H, benzimidazole4 H), 7.41 (t, J = 7.6 Hz, 2H, benzimidazole6 H),
7.22 (t, J = 7.8 Hz, 2H, benzimidazole5 H), 7.02 (s, 2H, central Ar3,5
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132.7 and 130.6 (Ph3,5 and Ph2,6), 125.3 (benzimidazole6), 123.6
(Ph1), 124.5 and 111.6 (benzimidazole4,5), 114.3 (benzimidazole7),
111.0 (central Ar3,5), 108.4 (CN), 69.0 (OCH2), 45.0 (NCH2), 32.1
(CH2), 31.3 (CH2), 20.1 (CH2), 19.4 (CH2), 14.1 (CH3), 13.8 (CH3).
19F NMR (400 MHz, CDCl3): δ −78.0. IR (KBr): ν 3432, 3098, 2960,
2871, 2254, 1598, 1522, 1450, 1389, 1268, 1156, 1027, 753, 635 cm−1.
Anal. Calcd for C40H42F3N5O4PtS (940.94): C, 51.06; H, 4.50; N,
7.44; Found: C, 50.93; H, 4.42; N, 7.40.
X-ray Diffraction Studies. Crystals of 3, 5, 8, 9, and 12 (CCDC
952608, 952610, 952611, 952612, and 952613, respectivelhy) were
obtained by recrystallization from CH2Cl2/n-hexane and those of 4
(CCDC 952609) from acetone at ambient temperature. The data were
collected on an Oxford Diffraction Gemini E diffractometer and
Bruker APEX-II CCD diffractometer (for 4) with graphite-
monochromated Mo Kα radiation (λ = 0.7107(3) Å) or Cu Kα
radiation (λ = 1.5418 Å, for complexes 8 and 12). The structures were
solved by direct methods using the SHELXS-97 program, and all non-
hydrogen atoms were refined anisotropically on F2 by the full-matrix
least-squares technique, which used the SHELXL-97 crystallographic
software package.25 The hydrogen atoms were included but not
refined. Details of the crystal structure determination of the Pt(II)
complexes are summarized in Table S2 in the Supporting Information.
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Y..; Ma, C.-W.; Che, C.-M. Angew. Chem., Int. Ed. 2009, 47, 9909.
(g) Wang, Z.; Turner, E.; Mahoney, V.; Madakuni, S.; Groy, T.; Li, J.
ASSOCIATED CONTENT
* Supporting Information
■
S
Text, figures, and tables giving information describing
instrumental methods used for characterization, photophysical
and spectroscopic studies, synthetic routes for ligands 2a−e,
1
selected H NMR data of ligands and complexes, crystallo-
graphic details for complexes 3−5, 8, 9, and 12, UV−vis
absorption spectra of complexes 3−15, pictures of the
representative FMOs, population analysis (%) of FMOs in
the ground state, Gaussian keywords and selected singlet
excited states calculated by TD-DFT as well as their
assignments for complexes 3−5, 8, 9, and 12, emission spectra
of complexes 3−15 in CH2Cl2, emission spectra of 5 and 12 at
different concentrations in CH2Cl2, emission spectra of
complexes 3−5 and 8−15 in the solid state and glassy 2-
MeTHF solution, NMR spectra of all the compounds 2−15,
CIF files giving crystallographic data for the six pincer Pt(II)
complexes, and a text file of all computed molecule Cartesian
coordinates in .xyz format for convenient visualization. This
material is available free of charge via the Internet at http://
pubs.acs.org.
́
Inorg. Chem. 2010, 49, 11276. (h) Mroz, W.; Botta, C.; Giovanella, U.;
Rossi, E.; Colombo, A.; Dragonetti, C.; Roberto, D.; Ugo, R.; Valorec,
A.; Williams, J. A. G. J. Mater. Chem. 2011, 21, 8653. (i) Rossi, E.;
Murphy, L.; Brothwood, P. L.; Colombo, A.; Dragonetti, C.; Roberto,
D.; Ugo, R.; Cocchi, M.; Williams, J. A. G. J. Mater. Chem. 2011, 21,
15501. (j) Rausch, A. F.; Murphy, L.; Williams, J. A. G.; Yersin, H.
Inorg. Chem. 2012, 51, 312. (k) Rao, Y.-L.; Schoenmakers, D.; Chang,
Y.-L.; Lu, J.-S.; Lu, Z.-H.; Kang, Y.; Wang, S. Chem. Eur. J. 2012, 18,
11306. (l) Rossi, E.; Colombo, A.; Dragonetti, C.; Roberto, D.;
Demartin, F.; Cocchi, M.; Brulatti, P.; Fattorie, V.; Williams, J. A. G.
Chem. Commun. 2012, 48, 3182. (m) Murphy, L.; Brulatti, P.; Fattori,
V.; Cocchi, M.; Williams, J. A. G. Chem. Commun. 2012, 48, 5817.
(n) Chen, Y.; Lu, W.; Che, C. -M. Organometallics 2013, 32, 350.
(5) Williams, J. A. G. Chem. Soc. Rev. 2009, 38, 1783.
AUTHOR INFORMATION
Corresponding Authors
* J.-F.G.: e-mail, gongjf@zzu.edu.cn.
*M.-P.S.: tel/fax, (+86)-371-6778-3012; e-mail, mpsong@zzu.
edu.cn.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(6) (a) Yip, H.-K.; Cheng, L.-K.; Cheung, K.-K.; Che, C.-M. J. Chem.
Soc., Dalton Trans. 1993, 2933. (b) Aldridge, T. K.; Stacy, E. M.;
McMillin, D. R. Inorg. Chem. 1994, 33, 722. (c) Bailey, J. A.; Hill, M.
G.; Marsh, R. E.; Miskowski, V. M.; Schaefer, W. P.; Gray, H. B. Inorg.
Chem. 1995, 34, 4591. (d) Lai, S.-W.; Chan, M. C. W.; Cheung, K.-K.;
We are grateful to the Specialized Research Fund for the
Doctoral Program of Higher Education (20114101130002) and
the National Natural Science Foundation of China (21072177
and 21172045) for financial support of this work. We also
thank Prof. Tao Yi from Fudan University for her kind
discussion and technical and instrument facility support.
Che, C.-M. Inorg. Chem. 1999, 38, 4262. (e) Buchner, R.;
̈
Cunningham, C. T.; Field, J. S.; Haines, R. J.; McMillin, D. R.;
Summerton, G. C. J. Chem. Soc., Dalton Trans. 1999, 711.
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