Synthesis, crystal structure, photophysical property and electropolymerization of Pt(II) complexes with carbazole-grafting 2-(2-pyridyl)benzimidazole

Article abstract of DOI:10.1016/j.inoche.2011.06.012

Two neutral-charged Pt(II) complexes, i.e., [(PBC)PtCl₂] (5) and [(PBC)Pt(C CC₆H₅)₂] (6) (PBC = N-[4-(9-carbazole)butyl]-2-(2-pyridyl)benzimidazole) have been synthesized and verified by ¹H NMR and X-

Full text of DOI:10.1016/j.inoche.2011.06.012

Inorganic Chemistry Communications 14 (2011) 1520–1524
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Synthesis, crystal structure, photophysical property and electropolymerization of
Pt(II) complexes with carbazole-grafting 2-(2-pyridyl)benzimidazole
⁎
Dongfang Qiu , Yingchen Guo, Hongwei Wang, Xiaoyu Bao, Yuquan Feng, Qunzeng Huang,
Junliang Zeng, Guozeng Qiu
College of Chemistry and Pharmacy Engineering, Nanyang Normal University, Nan yang, 473061, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Two neutral-charged Pt(II) complexes, i.e., [(PBC)PtCl2] (5) and [(PBC)Pt(C≡CC6H5)2] (6) (PBC=N-[4-(9-
carbazole)butyl]-2-(2-pyridyl)benzimidazole) have been synthesized and verified by 1H NMR and X-ray
crystallography. In each of them, the coordinate geometry of Pt atom is a distorted square planar configuration
with bond distances and angles in the normal range. Complex 6 shows an intense metal-to-ligand charge
transfer (1MLCT) (dπ(Pt)→π*(L)) transition at 412 nm in the UV-Vis absorption spectrum and a strong
phosphorescence at 593 nm in CH2Cl2 solution at ambient temperature. By selective optical-stimulation at
320 nm, an incomplete intramolecular energy transfer process from the carbazole unit to the [(PB)Pt
(C≡CC6H5)2] center results in unbalanced dual-emissive bands of a quenched carbazole-based luminescence
in deep blue region and an orange 3MLCT emission with increasing intensity. The introduction of carbazole
unit also triggers the electropolymerization of ligand PBC and complexes 5 and 6. The as-formed polymer film
from complex 5 has good conductivity, stability and clear anodic coloration effect.
Received 22 April 2011
Accepted 7 June 2011
Available online 16 June 2011
Keywords:
Pt(II) complex
Carbazole
2-(2-pyridyl)benzimidazole
Crystal structure
Photophysics
Electropolymerization
© 2011 Elsevier B.V. All rights reserved.
Multi-chromophoric systems have attracted great attention for
their potential applications in solar energy utilization [1], biological
probe [2], optical material [3], molecular device [4], supermolecular
assemble [5] and so on. Particularly, the research in white organic
light-emitting diodes (WOLEDs) has already been a hot area [6]. To
date, the most efficient WOLEDs have been designed by using site-
isolated block copolymer with a combination of either three different
chromophores emitting blue, green and red [7,8], or of two different
ones emitting green/blue and orange/red, in which the orange or red
chromophore is usually Ir(III) or Pt(II) phosphorescent complex [9].
Since the first luminescent Pt(II) acetylide complex with aromatic
diimine ligand was reported in 1994 [10], the photoluminescence of
platinum α-diimine bis(arylacetylide) complexes has been exten-
sively investigated. Eisenberg and co-workers synthesized a series of
[Pt(diimine)(C≡CAr)2] complexes by systematic ligand modifica-
tion, and probed the correlation between the emitting state [Pt→π*
(diimine) 3MLCT] energy and the electron-withdrawing nature of the
diimine auxiliary [11,12]. Che and co-workers subsequently reported
the development of these complexes towards application as photonic
material, which indicates that the [Pt(diimine)(C≡CAr)2] complex is a
class of promising candidate for OLEDs [13].
stronger π-donor, has been widely used as ‘bipyridine analogues’ in
coordination chemistry [14,15]. In particular, by introducing various
functional groups at the externally directed NH position of PB, the
derivatives and the corresponding metal complexes display the
interesting photoinduced electron- or energy-transfer between sites,
which have been proved to own a huge potential in the fields of
chemistry, biology and material science [16].
Carbazole and its derivatives are classic blue-emission and electro-
active materials with high triplet energy level and good charge
transport ability, widely utilized as hosters and charge transporters in
OLEDs [17–19], conductive electropolymers [20,21], and electrochro-
mic polymers [22]. However, integration of carbazole unit and the
emissive [Pt(PB)(C≡CAr)2] complex into a single molecule has so far
never been reported yet. Herein, we introduced a carbazole unit into
[(PB)PtCl2] and [(PB)Pt(C≡CAr)2] complexes through alkyl chain to
form bi-component complexes and studied their spectroscopic and
electrochemical behaviors.
The synthesis of Pt(II) complexes explored in this work are shown in
Scheme 1. 9-butyl-carbazole (1), 9-(4-bromobutane)carbazole (2) and
N-[4-(9-carbazole)butyl]-2-(2-pyridyl)benzimidazole (PBC) (4) were
synthesized according to literature methods [23,24]. Platinum(II)
dichloride complex (5) was obtained by stirring ligand PBC (4) and
[Pt(DMSO)2Cl2] [25] in CH2Cl2 for 24 h, followed by recrystallizing
from its CH2Cl2/MeOH solution [26]. Complex [(PBC)Pt(C≡CC6H5)2]
(6) was prepared by the reaction of [(PBC)PtCl2] (5) with arylace-
tylene under Sonogashira's condition (CuI/Et3N/CH2Cl2) and recrys-
tallization [27]. All the compounds were verified by 1H NMR and/or
Among the N,N′-diimine chelating ligands, 2-(2-pyridyl)
benzimidazole (PB), owing to the synthetic convenience and the
⁎
Corresponding author. Tel./fax: +86 377 63513595.
E-mail address: qiudf2008@gmail.com (D. Qiu).
1387-7003/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2011.06.012

D. Qiu et al. / Inorganic Chemistry Communications 14 (2011) 1520–1524
1521
Scheme 1. Synthetic route of Pt(II) complexes.
elementary analysis. Structure of complexes 5 and 6 were revealed by
X-ray crystallography [28].
By using slow evaporation method, green crystals of [(PBC)PtCl2]
(5) and orange crystals of [(PBC)Pt(C≡CC6H5)2] (6) were deposited
from their concentrated CH2Cl2/MeOH solutions, whose crystal data
and crystal structure parameters are listed in Table S1 and selected
bond lengths and angles are listed in Table S2, respectively.
Fig. 1 shows the perspective view of complex 5. The coordinate
geometry of Pt(II) ion displays the expected distorted square planar
configuration with bond distances and angles in the normal range for Pt
(II)-diimine complexes [13,16]. The chelating bite angle [N(1)–Pt(1)–N
(2)] of PBC ligand is 72.6(8)°. The configuration of benzimidazole
moiety in PBC ligand is basically a plane with the C(12)–C(7)–N(2)–C
(6) torsion angle of 3(3)°. The dihedral angle between the pyridyl
ring and the benzimidazole plane of PBC ligand is 4.0°. The double bond
[N(2)–C(6)] of the five-membered imidazole ring is evidently the
shortest of all bonds in PBC ligand, at 1.07(3) Å. The peripheral carbazole
unit is approximately planar with the C(21)–C(22)–C(23)–C(24)
torsion angle of 13(6)°. The dihedral angle between the peripheral
carbazole moiety and the benzimidazole unit of the PBC ligand is 85.1°.
The crystal lattice of complex 5 is packed by one kind of alternating
arranged dimeric units (Figure S1). Two [(PBC)PtCl2] molecules in
each dimeric unit are stacked in a head-to-tail fashion with a Pt-Pt
distance of 5.060 Å, suggesting no metal–metal interaction, and are
likely to be held together by the weak π–π interaction between their
PB moieties which is indicated by the dihedral angle of 2.5° and the
interplanar separation of 3.513 Å.
Fig. 1. Perspective view of 5 with the numbering scheme adopted (hydrogen atoms
have been omitted for clarity).

1522
D. Qiu et al. / Inorganic Chemistry Communications 14 (2011) 1520–1524
Fig. 2. Perspective view of 6 with the numbering scheme adopted (hydrogen atoms have been omitted for clarity).
The Pt(II) complex 6 (Fig. 2) also has essentially square planar
dominated by 1IL (π→π*) transitions [29,30], while the low-energy
bands with λmax at 398 nm and 412 nm in the absorption spectra
of 5 and 6 (Figure S3) were assigned to the spin-allowed singlet
dπ(Pt)→π*(L) metal-to-ligand charge transfer (1MLCT) transition
[30]. Compared to those of the reported derivatives of 2-(2-pyridyl)
benzimidazole (PB) with Pt(II) [13,16], no apparent change in the
long-wavelength region of the absorption spectrum was observed for
6, suggesting the introduction of carbazole unit through alkyl chain
doesn't influence the energy levels of the [(PB)Pt(C≡CC6H5)2] center.
This effect is accorded with the previously reported result in the Re(I)
analogue [29].
coordination geometry with bond distances and angles similar to com-
plex 5, such as the chelating bite angle [N(1)–Pt(1)–N(3)] of 77.8(17)°,
the planar configuration of benzimidazole moiety withthe C(6)–C(1)–N
(1)–C(7) torsion angle of 1.2°, the larger dihedral angle between the
pyridyl ring and the benzimidazole plane of 12.6° in PBC ligand and the
shortest double bond [N(1)–C(7)] at 1.333(6) Å among all bonds of
the five-membered imidazole ring. The Pt–N(benzimidazole) distance
[2.056(4) Å] is slightly shorter than the Pt–N(2-pyridyl ring) distance
[2.074(4) Å], which is similar to the reported analogues [16]. The Pt–N
bond lengths in complex 6 are marginally shorter than those in complex
5, reflecting the smaller trans influence of phenylacetylide in compari-
sion to chloride. The C≡C bonds have distances of 1.212(7) Å forC(29)–C
(30) and 1.226(7) Å for C(37)–C(38), in obvious contrast to the im-
mediatelyfollowing C–C single bonds of 1.420(8) Å for C(30)–C(31) and
1.423(8) Å for C(38)–C(39). The dihedral angles between the benzene
ring in each phenylacetylide moiety and the Pt(II)-centred coordinate
plane are 25.5 and 54.3°, respectively. The dihedral angle between the
peripheral carbazole plane with the C(21)–C(22)–C(23)–C(24) torsion
angle of 3.6° and the benzimidazole unit of the PBC ligand is 15.0°.
Multiple close intermolecular contacts were revealed upon
inspection of the packing diagram (Figure S2) of complex 6 (e.g. C
(1)···C(6′) 3.482, C(6)···C(1′) 3.482, N(1)···C(27′) 3.521, C
(12)···C(22′) 3.458, C(12)···C(17′) 3.518 Å). These distances are
sufficiently short for π–π interactions, and indeed π stacking of PB
moieties and PB moieties with the neighboring carbazole planes is
apparent. The longer Pt–Pt distance of 7.844 Å was observed, arising
from the steric effect of phenylacetylide units.
The photoluminescence (PL) properties of compounds 1, 4, 5 and
6 are also listed in Table 1. Three distinct emission waves were observed
for compound 1 in CH2Cl2 solution. Owing to the molecular aggregation
effect, large bathochromic shift of the three emission waves was found
Table 1
UV–vis and PL data of the compounds.
Compound UV–vis, λmax(nm)
(ε×103 dm3 mol−1cm−1
PL, λmax(nm)(Фa)
in fluid solutionb
350, 368, 385(sh)
)
in solid state
1
4
5
6
332(3.5), 294(14.0),
264(20.0)
418, 436, 460(sh)
346(3.3), 313(21.4),
295(29.8), 264(19.5)
398(3.9), 344(16.1),
332(17.3), 294(23.8)
412(7.8), 344(22.2),
330(25.1), 294(50.7)
352, 369, 384(sh), 414, 434, 462(sh)
429(sh)
–
–
593(0.030)c,
588(0.058)d
574c
a
Quantum yield was calculated using [Ru(bpy)3]2+ in aerated water (Ф=0.028)
Table 1 summarizes the absorption maxima and extinction co-
efficients of the absorption bands for the obtained compounds. The
intense absorption bands in the high-energy region (λb350 nm)
were observed in the absorption spectra of 1 and 4, which are
as reference.
b
Measured in CH2Cl2 solution at 298 K (concentration~1×10-5 mol dm−3).
Excited wavelength: 410 nm.
Excited wavelength: 320 nm.
c
d

D. Qiu et al. / Inorganic Chemistry Communications 14 (2011) 1520–1524
1523
in solid state. PBC (4) showed a weak emission wave at 429 nm in
CH2Cl2 solution besides the above-mentioned waves of carbazole unit,
which is arise from the 2-(2-pyridyl)benzimidazole (PB) moiety. No
apparent emissive wave was observed for complex 5, while complex
6 exhibited an intense 3MLCT emission at 593 nm in fluid solution and a
blue-shifted emission at 574 nm in solid state at room temperature,
resulting from the incorporation of strong-field ligand of acetylide to
destabilize nonradiative ligand-field transitions [4].
based and carbazole-based waves, indicating the presence of a
conductive poly-5 film on the Pt electrode. These results reflect that
introduction of a carbazole unit in PBC triggers the cross-linkingreaction
following an E(CE)n-type mechanism [31], and that the generated
3,6-polycarbazole is more easily oxidized than the parent compound,
which are in agreement with those of carbazole and its derivatives [32].
Pale green poly-PBC and poly-6 films were also obtained by the
oxidative electropolymerization of PBC and 6 monomers (Figure S5),
however, their anodic and cathodic currents gradually decreased during
theelectropolymerization process, suggestingtheir weakconductivities.
Fully washed with CH2Cl2 and ethanol to remove the unreacted
monomer and oligomeric species, poly-5 film showed the linear
increase of the anodic and cathodic currents with the scan rate in
monomer-free electrolytic solution (Figure S6) and a good stability
upon over hundreds of potential sweep cycles from 0 to 1.8 V at the
scan rate of 100 mV s−1, indicating the polymer film adheres well to
the Pt electrode. Figure S7 shows the AC impedance spectra of poly-5
film modified Pt electrodes after various potential sweeping cycles,
measured in the frequency range from 1 to 100 kHz at 0.38 V vs. SCE
with the presence of 1.0 mmol L−1 Ferrocene as a redox probe in
0.1 mol L−1 Bu4NClO4/CH2Cl2 solution. Every spectrum is fitted by a
semicircle at high frequencies and the diameter of fitted semicircle
decreases with the scan number. Because the diffusion component of
impedance is negligible at high frequencies, the diameter of semicircle
is responsible for the resistance of electron transfer in the polymer
film.
The spectroelectrochemical properties of poly-5 film on transpar-
ent ITO electrode after 15 potential sweeping cycles were performed
at various applied potentials (Fig. 4). A low-energy absorption wave
was gradually formed and blue-shifted to ca. 722 nm with positive
increase of the applied potential. This result is in agreement with that
of the oxidized biscarbazole reported previously [33], reconfirming
that the dimerization of the carbazole moiety of PBC is involved in the
electropolymerization process. The polymer film underwent a clear
color change from pale green to dark green, suggesting its promising
potential in electrochromic materials.
Herein, the N,N′-diimine derivative of carbazole-grafted 2-(2-
pyridyl)benzimidazole and its corresponding Pt(II) chloride and bis
(arylacetylide) complexes have been synthesized and verified success-
fully. The XRD determinations reveal that the coordinate geometry of
the Pt atom is a distorted square planar configuration with bond dis-
tances and angles in the normal range for each complex. The two Pt(II)
complexes show different crystal packing configuration arising from
the steric effect of the grafting carbazole and phenylacetylene units.
In contrast to the Pt(II) chloride, the Pt(II) bis(arylacetylide) complex
displays a strong phosphorescence at 593 nm in CH2Cl2 solution at
For the emissive bi-component complex 6, selective optical-
stimulation experiments were conducted to study the interaction
between sites (Figure S4). Excited at 410 nm, which was into the
Pt(II)-based MLCT absorption band, complex 6 displayed a strong 3MLCT
emission at 593 nm with the quantum yield of 0.030, which is
comparable to the Pt(II) analogues [7] and is much higher than the
similar Re(I) complex [29]. While excited at 320 nm, which was into
the carbazole absorption band in the UV region, complex 6 displayed
a residual carbazole-based emission band at 363 nm in addition
to the 3MLCT band at λmax =588 nm. The higher energy carbazole-
based luminescence was dramatically quenched, compared with
those of compound 1 or the physical mixture of compound 1 and
complex 6 (molar ratio=1:1) under the same experimental con-
dition. The quenching efficiency ([1−(A/A0)]×100(%)) is 94%, in
which A and A0 stand for the integrated area from 330 nm to 500 nm
in the emission spectra of complex 6 and compound 1, respectively.
And the intensity of the 3MLCT emission band clearly increased
compared to that of complex 6 excited at 410 nm. The enhanced
fluorescence efficiency ([(A2/A1)−1]×100(%)) is ca. 94%, in which A2
and A1 stand for the integrated area from 475 nm to 850 nm in the
emission spectra of complex 6 excited at 320 and 410 nm, respectively.
These results suggest that an incomplete intramolecular energy trans-
fer process from the carbazole unit to the [(PB)Pt(C≡CC6H5)2] emissive
center exists in complex 6 and the energy conversion efficiency is close
to 100%.
The electrochemical polymerization (EP) of [(PBC)PtCl2] (5) was
carefully studied via continuously cycling of the working Pt electrode
potential from 0 to 1.8 V with the scan rate of 50 mV s−1 in 0.1 mol L−1
Bu4NClO4/CH2Cl2 solution containing 5.0×10−4 mol L−1 monomer. A
clear oxidation peak at Ep=+1.25 V (vs. SCE) and a broad wave at
higher potential were observed in the first anodic scan (Fig. 3). With
reference to the first CV curve of PBC, they were assigned to the sep-
arated oxidation processes of Pt(II) center and carbazole unit in PBC,
respectively. In the second anodic scan, a new wave at Ep=+0.95 V
(vs. SCE) appeared, suggesting that new electroactive species are
generated after the first CV scan, and the carbazole-based oxidation
wave negatively shifted to +1.37 V. As the cyclic scan proceeded,
intensities of anodic and cathodic currents gradually increased with the
formation of a broad oxidation wave from overlapping of the Pt(II)-
Fig. 3. Repetitive cyclic voltammograms of 5 on a Pt electrode.
Fig. 4. Spectroelectrochemical behavior of poly-5 coated ITO.

1524
D. Qiu et al. / Inorganic Chemistry Communications 14 (2011) 1520–1524
[13] S.C. Chan, M.C.W. Chan, Y. Wang, C.M. Che, K.K. Cheung, N. Zhu, Organic light-
emitting materials based on Bis(arylacetylide)platinum(II) complexes bearing
substituted bipyridine and phenanthroline ligands: photo- and electrolumines-
cence from 3mlct excited states, Chem. Eur. J. 7 (2001) 4180–4190.
ambient temperature, resulting from the incorporation of strong-field
ligand of acetylide to destabilize nonradiative ligand-field transitions.
Meanwhile, by selective optical-stimulation, an incomplete intramo-
lecular energy transfer process from the carbazole unit to the Pt(II)-
based emissive center was observed, resulting in unbalanced dual-
emissive bands of a quenched carbazole-based luminescence in deep
blue region and an orange 3MLCT emission with increasing intensity.
The electrochemical studies suggested that the introduction of car-
bazole unit through alkyl chain in ligand and complexes can trigger
the efficient cross-linking reaction to form polymer films. Poly-5 films
with high conductivity, good stability and clearly anodic coloration
exhibited promising potential in electrochromic applications.
[14] C. Piguet, G. Bernardinelli, G. Hopfgartner, Helicates as versatile supramolecular
complexes, Chem. Rev. 97 (1997) 2005–2062.
[15] R. Boca, P. Baran, L. Dlhán, J. Sima, G. Wiesinger, F. Renz, U. El-Ayaan, W. Linert,
Complete spin crossover in Tris(Pyridylbenzimidazole) Iron(II), Polyhedron 16
(1997) 47–55.
[16] N.M. Shavaleev, Z.R. Bell, T.L. Easun, R. Rutkaite, L. Swanson, M.D. Ward, Complexes of
substituted derivatives of 2-(2-pyridyl)benzimidazole with Re(I), Ru(II) and Pt(II):
structures, redox and luminescence properties, Dalton Trans. (2004) 3678–3688.
[17] W. Lu, M.C.W. Chan, N. Zhu, C.M. Che, C. Li, Z. Hui, Light-emitting tridentate
cyclometalated platinum(II) complexes containing σ-alkynyl auxiliaries: tuning
of photo- and electrophosphorescence, J. Am. Chem. Soc. 126 (2004) 7639–7651.
[18] D.F. Qiu, J. Wu, Z.Y. Xie, Y.X. Cheng, L.X. Wang, Synthesis, photophysical and
electrophosphorescent properties of mononuclear Pt(II) complexes with arylamine
functionalized cyclometalating ligands, J. Organomet. Chem. 694 (2009) 737–746.
[19] J.Q. Ding, B. Wang, Z.Y. Yue, B. Yao, Z.Y. Xie, Y.X. Cheng, L.X. Wang, X.B. Jing, F.S.
Wang, Bifunctional green iridium dendrimers with a “self-host” feature for highly
efficient nondoped electrophosphorescent devices, Angew. Chem. Int. Ed. 48
(2009) 6664–6666.
[20] Q. Wang, J.Q. Ding, D.G. Ma, Y.X. Cheng, L.X. Wang, F.S. Wang, Manipulating
charges and excitons within a single-host system to accomplish efficiency/CRI/
color-stability trade-off for high-performance OWLEDs, Adv. Mater. 21 (2009)
2397–2401.
[21] J.Q. Ding, J.H. Lü, Y.X. Cheng, Z.Y. Xie, L.X. Wang, X.B. Jing, F.S. Wang, Solution-
processible red iridium dendrimers based on oliocarbazole host dendrons:
synthesis, properties, and their applications in organic light-emitting diodes,
Adv. Funct. Mater. 18 (2008) 2754–2762.
Acknowledgments
This work is supported by the Natural Science Foundation of
Henan Province (No: 102300410221), the Natural Science Founda-
tion of Nanyang Normal University (No: ZX2010012) and the Project
supported by the Young Core Instructor from the Education Commission
of Henan Province.
Appendix A. Supplementary material
[22] Z. Wei, J. Xu, G. Nie, Y. Du, S. Pu, Low-potential electrochemical polymerization of
carbazole and its alkyl derivatives, J. Electroanal. Chem. 589 (2006) 112–119.
[23] Q. Zhao, D. Qiu, Y. Guo, Y. Feng, C. Zhou, D. Liu, Synthesis, crystal structure,
photophysical and redox properties of a novel Ru(II) complex with carbazole-
grafted 2-(2-Pyridyl)benzimidazole, Chin. J. Struct. Chem. 30 (2011) 417–423.
[24] D.F. Qiu, Y.Q. Feng, H.W. Wang, X.Y. Bao, Y.C. Guo, Y.X. Cheng, L.X. Wang,
Crystal packing diagrams, UV-vis and PL spectra, CVs, AC
impedance spectra. Crystallographic data for the structure reported
in this paper have been deposited with Cambridge Crystallographic
Data Center as supplementary publication no. CCDC-775606 and
CCDC-782293. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.
uk/data request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/j.inoche.2011.06.
012.
Synthesis, crystal Structure and photophysical properties of
a novel Pt(II)
complex with multi-functionalized cyclometalating ligand, Inorg. Chem. Com-
mun. 13 (2010) 613–617.
[25] W. Kitching, C.J. Moore, D. Doddrell, Spectroscopic studies of alkyl sulfoxide
complexes of platinum(II) and palladium(II), Inorg. Chem. 9 (1970) 541–549.
[26] Synthesis of complex [(PBC)PtCl2] (5): A solution of [Pt(DMSO)2Cl2] (43.8 mg, 0.1
mmol) and ligand PBC (42.9 mg, 0.1 mmol) in CH2Cl2 (10 mL) was stirred under
an Ar atmosphere for 24 h. After the centrifugal separation, the crude product was
purified by recrystallizing from CH2Cl2/MeOH solution to give green crystals:
0.051 g (yield: 74.7 %). 1H NMR (300 MHz, DMSO-d6): δ 9.59 (d, J = 5.7 Hz, 1H),
8.91 (d, J = 8.4 Hz, 1H), 8.33–8.22 (m, 2H), 8.12 (d, J = 7.5 Hz, 2H), 7.89 (d, J = 8.1
Hz, 1H), 7.79 (t, J = 6.3 Hz, 1H), 7.57 (d, J = 8.1 Hz, 2H), 7.50 (t, J = 7.5 Hz, 1H),
7.41 (t, J = 7.5 Hz, 3H), 7.18 (t, J = 7.5 Hz, 2H, Ar), 4.83 (broad, 2H), 4.39 (broad,
2H), 1.94 (broad, 4H, –CH2–).
[27] Synthesis of complex [(PBC)Pt(C≡CC6H5)2] (6): [(PBC)PtCl2] (68.2 mg, 0.1 mmol),
CuI (5 mg, 0.025 mmol) and Et3N 5 mL were added to dichloromethane (50 mL).
After the addition of freshly distilled phenylacetylene (76.2 mg, 0.89 mmol), the
resultant mixture was stirred under an Ar atmosphere in the absence of light at room
temperature for 12 h. The crude product was obtained using the centrifugal
separation and purified by recrystallizing from CH2Cl2/MeOH solution twice to give
orange crystals: 0.059 g (yield: 65.6 %). 1H NMR (300 MHz, CDCl3): δ 8.56 (d, J = 4.2
Hz, 1H), 8.22 (d, J = 7.2 Hz, 1H), 7.96 (d, J = 7.8 Hz, 2H), 7.63 (d, J = 8.1 Hz, 1H), 7.42
(d, J = 7.5 Hz, 4H), 7.32–7.26 (m, 7H), 7.22–7.11(m, 8H), 6.97 (t, J = 7.5 Hz, 1H), 6.78
(t, J = 6.6 Hz, 1H, Ar), 4.96 (t, J = 7.5 Hz, 2H), 4.23 (t, J = 6.6 Hz, 2H), 2.00 (m, 2H),
1.76 (m, 2H, –CH2–).
[28] Diffraction data was collected on a Bruker SMART APEX II CCD diffractometer
equipped with a graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å)
using a Φ-ω scan mode. The intensity data were corrected by Lp factors and
empirical absorption.The structure was solved by direct methods and subsequent
successive difference Fourier maps, and refined by full-matrix least-squares
techniques on F2. All of the non-hydrogen atoms were refined anisotropically. The
organic hydrogen atoms were generated geometrically. All calculations were
carried out with SHELXTL-97 program.
[29] Z. Si, J. Li, B. Li, F. Zhao, S. Liu, W. Li, Synthesis, structural characterization, and
electrophosphorescent properties of rhenium(I) complexes containing carrier-
transporting groups, Inorg. Chem. 46 (2007) 6155–6163.
[30] Q. Liu, W. Jia, S. Wang, Blue luminescent 2-(2’-pyridyl)benzimidazole derivative
ligands and their orange luminescent mononuclear and polynuclear organopla-
tinum(II) complexes, Inorg. Chem. 44 (2005) 1332–1343.
References
[1] D. Bellows, S.M. Aly, C.P. Gros, M.E. Ojaimi, J.M. Barbe, R. Guilard, P.D. Harvey,
Energy transfer in monomers, dimers, and trimers of zinc(II) and palladium(II)
porphyrins bridged by rigid Pt-containing conjugated organometallic spacers,
Inorg. Chem. 48 (2009) 7613–7629.
[2] K.K.W. Lo, K.Y. Zhang, S.K. Leung, M.C. Tang, Exploitation of the dual-emissive
properties of cyclometalated iridium(III)-polypyridine complexes in the devel-
opment of luminescent biological probes, Angew. Chem. Int. Ed. 47 (2008)
2213–2216.
[3] E. Deniz, M. Tomasulo, S. Sortino, F.M. Raymo, Substituent effects on
the photochromism of bichromophoric oxazines, J. Phys. Chem. C 113 (2009)
8491–8497.
[4] V.J. Chebny, R. Shukla, S.V. Lindeman, R. Rathore, Molecular actuator: redox-
controlled clam-like motion in a bichromophoric electron donor, Org. Lett. 11
(2009) 1939–1942.
[5] B.B. Wang, M. Gao, X.R. Jia, W.S. Li, L. Jiang, Y. Wei, Photoinduced energy transfer
in bichromophoric co-assemblies based on amphiphilic poly(amidoamine)
dendrons, J. Colloid Interface Sci. 324 (2008) 225–229.
[6] D.A. Poulsen, B.J. Kim, B. Ma, C.S. Zonte, J.M.J. Fréchet, Site isolation in
phosphorescent bichromophoric block copolymers designed for white electrolu-
minescence, Adv. Mater. 22 (2010) 77–82.
[7] J. Liu, Q.G. Zhou, Y.X. Cheng, Y.H. Geng, L.X. Wang, D.G. Ma, X.B. Jing, F.S. Wang, The
first single polymer with simultaneous blue, green, and red emission for white
electroluminescence, Adv. Mater. 17 (2005) 2974–2978.
[8] J. Liu, Q.G. Zhou, Y.X. Cheng, Y.H. Geng, L.X. Wang, D.G. Ma, X.B. Jing, F.S. Wang,
White electroluminescence from a single-polymer system with simultaneous
two-color emission: polyfluorene as the blue host and a 2,1,3-benzothiadiazole
derivative as the orange dopant on the main chain, Adv. Funct. Mater. 16 (2006)
957–965.
[9] E. Holder, B.M.W. Langeveld, U.S. Schubert, New trends in the use of transition
metal–ligand complexes for applications in electroluminescent devices, Adv.
Mater. 17 (2005) 1109–1121.
[10] C.W. Chan, L.K. Cheng, C.M. Che, Luminescent donor-acceptor platinum(II)
complexes, Coord. Chem. Rev. 132 (1994) 87–97.
[11] W.B. Connick, D. Geiger, R. Eisenberg, Excited-state self-quenching reactions of
square planar platinum(II) diimine complexes in room-temperature fluid
solution, Inorg. Chem. 38 (1999) 3264–3265.
[12] M. Hissler, W.B. Connick, D.K. Geiger, J.E. McGarrah, D. Lipa, R.J. Lachicotte, R.
Eisenberg, Platinum diimine Bis(acetylide) complexes: synthesis, characterization
and luminescence properties, Inorg. Chem. 39 (2000) 447–457.
[31] G. Inzelt, Formation and redox behaviour of polycarbazole prepared by
electropolymerization of solid carbazole crystals immobilized on an electrode
surface, J. Solid State Electrochem. 7 (2003) 503–510.
[32] C. Gu, T. Fei, Y. Liu, T. Feng, S. Xue, D. Lu, Y. Ma, Color-stable white
electroluminescence based on
a cross-linked network film prepared by
electrochemical copolymerization, Adv. Mater. 22 (2010) 2702–2705.
[33] J. Natera, L. Otero, L. Sereno, F. Fungo, N. Wang, Y. Tsai, T. Hwu, K. Wong, A novel
electrochromic polymer synthesized through electropolymerization of a new
donor-acceptor bipolar system, Macromolecules 40 (2007) 4456–4463.