Synthesis, crystal structure and photophysical properties of a novel Pt(II) complex with multi-functionalized cyclometalating ligand

Article abstract of DOI:10.1016/j.inoche.2010.02.016

A novel Pt(II) complex [(L)PtCl] (HL = 4-{p-[N-(4-(9-carbazole))butyl-N-phenyl] aniline}-6-phenyl-2,2′-bipyridine) has been synthesized and verified by ¹H NMR, elemental analysis and X-ray crystallography. The crystal (C₄₄H₃₅

Full text of DOI:10.1016/j.inoche.2010.02.016

Inorganic Chemistry Communications 13 (2010) 613–617
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Synthesis, crystal structure and photophysical properties of a novel Pt(II) complex
with multi-functionalized cyclometalating ligand
a
a
a
a
Dongfang Qiu a, , Yuquan Feng , Hongwei Wang , Xiaoyu Bao , Yingchen Guo ,
⁎
Yanxiang Cheng b, Lixiang Wang b
College of Chemistry and Pharmacy Engineering, Nan yang Normal University, Nan yang, 473061, PR China
a
b
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel Pt(II) complex [(L)PtCl] (HL=4-{p-[N-(4-(9-carbazole))butyl-N-phenyl] aniline}-6-phenyl-2,2′-bipyr-
idine) has been synthesized and verified by 1H NMR, elemental analysis and X-ray crystallography. The crystal
(C44H35N4ClPt, Mr=850.30) belongs to monoclinic system, space group P2(1)/c, with a=21.864(6), b=9.306
Received 3 February 2010
Accepted 23 February 2010
Available online 1 March 2010
(3), c=17.240(5) Å, β=96.483(6)°, Z=4, V=3485.3(16) Å3, DC =1.620 g/cm3, μ(Mo-Kα)=4.141 mm−1
,
F(000)=1688, R1 =0.0591, wR2 =0.0976. The coordinate geometry of the Pt atom is a distorted square
planar configuration. The complex molecules are stacked by a weak π–π interaction in a head-to-tail fashion along
the b axis to form 1D chain and the alternating 1D chains are packed to form the 2D lamellar system. The complex
shows an intense metal-to-ligand charge transfer (1MLCT) (dπ(Pt)→π*(L)) transitions (ε ∼2×104 dm3 mol−1
cm−1) at 448 nm in the UV–Vis absorption spectrum and a strong phosphorescence at 592 nm in CH2Cl2 solution
at room temperature. An intramolecular energy transfer process from the carbazole unit to the arylamine-
modified [(C^N^N)PtCl] emissive center exists in the complex.
Keywords:
Platinum (II)
Cyclometalated
Multi-functionalized
Crystal structure
Photophysics
© 2010 Elsevier B.V. All rights reserved.
Cyclometalated Pt(II) complexes with the (C^N^N) tridentate
ligand have recently received considerable interest in organic light-
emitting diodes (OLEDs) [1–5]. At room temperature, [(C^N^N)Pt]
complexes are phosphorescent emitting materials with high quantum
yields since the strong ligand field effect of the cyclometalated carbon
raises the energy of the d–d transitions, the moderate σ-donating and
π-accepting abilities of (C^N^N) ligand properly satisfy the demand of
the Pt(II) coordination geometry of the square plane to discourage the
D2d distortion which is likely to result in a non-radiactive decay [6,7].
Our group [8] integrated hole-transporting arylamine into the
[(C^N^N)Pt] phosphorescent emitting center to form a novel class of
multifunctional complexes. The bathochromically shifted maxima in
the absorption and emission spectra indicate that the incorporation of
an electron-rich group into the electron-deficient pyridine moiety can
strengthen the donor–acceptor (D–A) interaction. The resulting
complexes display stronger phosphorescence in CH2Cl2 solutions at
room temperature with relatively higher quantum yields and much
longer lifetimes. An orange multilayer organic light-emitting diode,
used [(L2)PtCl] (HL2 =4-[p-(N-butyl-N-phenyl)anilino]-6-phenyl-
2,2′-bipyridine) as phosphorescent dopant, was fabricated, achieving
a maximum current efficiency of 11.3 cd A–1 and a maximum external
efficiency of 5.7%.
Carbazole and its derivatives are classic blue-emission and electro-
active materials, widely utilized as hosters and charge transporters in
OLEDs [9–11], conductive electropolymers [12,13], and electrochro-
mic polymers [14]. In this paper, we further introduced a carbazole
unit into [(L2)PtCl] complex through alkyl chain to form tri-functional
complex and studied its photo-physical behaviors. The fundamental
design considerations are to 1) integrate the hoster and dopant into
one molecule to simplify the production process of OLEDs; 2) maintain
spectral property of each component separately, which can help to
study the interaction between them by selective optical- and electro-
stimulation.
The synthesis of ligand and complex explored in this work are
shown in Scheme 1. Carbazole directly coupled with excess 1, 4-
dibromobutane under strong basic condition to afford 9-(4-bromo-
butane)carbazole (1) [15]. 4-(p-bromophenyl)-6-phenyl-2,2′-bipyr-
idine was obtained using Kröhnke's method [16]. The powerful
palladium-catalyzed Buchwald method and the efficient Pd(OAc)2/
DPEphos catalyst/ligand system [17] were adopted to facilitate the
condensation of aniline with 4-(p-bromophenyl)-6-phenyl-2,2′-
bipyridine. Then the resulting intermediate (2) reacted with 9-(4-
bromobutane) carbazole (1) to afford the ligand HL (3) [18]. The
cyclometalated Pt(II) chloride 4 was synthesized by refluxing the ligand
HL (3) and K2PtCl4 in glacial acetic acid for 24 h in over 80% yield [19].
The single crystal of 4 was grown by slowly evaporating the
solvent from its concentrated CH2Cl2/MeOH solution; its crystal data
and crystal structure parameters are listed in Table 1 and the details of
⁎
Corresponding author. Tel./fax: +86 377 63513595.
E-mail address: qiudf2008@gmail.com (D. Qiu).
1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2010.02.016

614
D. Qiu et al. / Inorganic Chemistry Communications 13 (2010) 613–617
Scheme 1. Synthetic route of the Pt(II) complex.
the data collection, structure solution and refinement are given in
[20]. Fig. 1 shows the perspective view of complex 4. The coordinate
geometry of the Pt atom is a distorted square planar configuration
with the C(1)-Pt(1)-N(2) and N(1)-Pt(1)-Cl(1) angles of 160.72(16)
and 179.30(11)°. The bond distances of Pt-C(1), Pt-N(1) and Pt-N(2)
are 2.021(4), 1.868 (3) and 2.082 (4) Å, respectively, which are
comparable to those of previously reported analogous [21–24]. The
configuration of C^N^N ligand is basically a plane with the C(1)-C(6)-
C(7)-N(1) and N(2)-C(12)-C(11)-N(1) torsion angles of 2.40 and
0.76°. The dihedral angle between the phenyl ring at 4-position of the
C^N^N ligand and the plane of the [(C^N^N)Pt] moiety is 23.75°. The
geometry of the N(3) atom is a distorted tetrahedral configuration
with the C(20)-N(3)-N(28), C(20)-N(3)-N(29) and C(28)-N(3)-N
(29) angles of 119.3(4), 120.2(4) and 115.6(4)°. The peripheral
carbazole unit is approximately a plane with the C(37)-C(38)-C(39)-C
(40) torsion angle of 4.75°.
Instead of forming a continuous chain with Pt–Pt linkage in
[(C^N^N)PtCl] [23,24] or a alternating arranged dimer [8], the
complex molecules are stacked in a head-to-tail fashion along the b
axis to form 1D chain (Fig. 2) with a Pt–Pt distance of 6.245 Å,
suggesting no metal–metal interaction. The [(C^N^N)PtCl] moieties
are almost parallel with the least dihedral angle of 0.106°, and their
interplanar separation of 3.383 Å indicates that they are likely to be
held together by a weak π–π interaction. The alternating 1D chains are
packed to form the 2D lamellar system with the dihedral angle of
82.620° between the [(C^N^N)PtCl] moieties in neighboring chains.
Table 2 summarizes the absorption maxima and extinction
coefficients of the absorption bands for the obtained compounds
Table 1
Crystal data and crystal structure parameters.
Complex
Value
Empirical formula
Formula weight
Temperature/K
Wavelength/Å
Crystal system
Space group
a/Å
b/Å
c/Å
α/(°)
β/(°)
C
44H35ClN4Pt
850.30
296(2)
0.71073
Monoclinic
P2(1)/c
21.864(6)
9.306(3)
17.240(5)
90.00
96.483(6)
90.00
3485.3(16)
γ/(°)
Volume/Å3
Z
4
Dc/(mg m–3
)
1.620
4.141
1688
0.17×0.14×0.07
2.38 to 25.00
−17≤h≤25,−11≤k≤10,−20≤l≤20
99.5%
6101/2/451
Absorption coefficient/mm–1
F(000)
Crystal size/mm
θ range for data collection/(°)
Limiting indices
Completeness to θ=25.00°
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [IN2σ(I)]
R indices (all data)
0.931
R1 =0.0591, wR2 =0.0841
R1 =0.1566, wR2 =0.0976
1.180 and−0.978
Largest diff. peak and hole/(e Å–3
)

D. Qiu et al. / Inorganic Chemistry Communications 13 (2010) 613–617
615
Fig. 1. Perspective view of 4 with the numbering scheme adopted (hydrogen atoms have been omitted for clarity).
and Fig. 3 shows the long-wavelength region of the absorption spectra
for ligand HL (3) and the corresponding Pt (II) complex (4). The
intense absorption bands in the high-energy region (λb376 nm) with
extinction coefficients (ε) of the order of 104 dm3 mol–1 cm–1 were
observed in the absorption spectra of 3 and 4, which are dominated by
1IL (π→π*) transitions, while the low-energy band with λmax at
448 nm in the absorption spectrum of 4 is assigned to the spin-
allowed singlet dπ(Pt)→π*(L) metal-to-ligand charge transfer
(1MLCT) transitions. Owing to the strong D–A interaction between
the amine unit and the C^N^N cyclometalating ligand [8], the molar
extinction coefficient of the MLCT band is 2–3 times larger than those
of the reported C^N^N cyclometalated Pt(II) complexes [1,2].
Compared to that of the reported complex [(L2)PtCl], no apparent
change in the long-wavelength region of the absorption spectrum was
observed for 4, suggesting the introduction of carbazole unit through
alkyl chain has no influence on the energy level of the [(L2)PtCl]
moiety.
The PL properties of compounds in CH2Cl2 solution are listed in
Table 3. Three distinct emission bands are observed for 9-(4-
Bromobutane)carbazole (1) in CH2Cl2 solution and in solid state
Fig. 3. UV–vis absorption spectra of ligand HL (3) and complex (4).
Table 3
Fig. 2. 2D lamellar packing diagram of
4 (hydrogen atoms and the Carbazole-
PL data of the compounds.
substituted phenylamino units have been omitted for clarity).
Compound
λ
max(nm)(Фa)
λ
max(nm)
λmax(nm)
In fluid solutionb
In alcoholic glassc
In solid states (298 K)
Table 2
1
350, 368, 385(sh)
462
592(0.10 )
595(0.11)
–
418, 436, 460(sh)
446
612
Absorption maxima of the compounds in CH2Cl2 solutions at 298 K.
3
–
4d
582, 622
581, 624
Compound
λ )
max(nm)(ε×103 dm3 mol–1 cm–1
[(L2)PtCl]d
604, 625(sh)
1
3
4
332(3.5), 294(14.0), 264(20.0)
346(28.5), 294(37.0), 262(50.9)
448(19.8), 376(20.6), 328(27.2), 294(55.3), 264(75.3)
449(20.6), 373(18.6), 327(21.4), 279(33.3)
a
[Ru(bpy)3](PF6)2 in degassed acetonitrile at 298 K (Фr =0.062) as reference.
Measured in degassed CH2Cl2 solutions at 298 K (concentration∼1×10–5 mol dm–3).
Measured in CH3OH/C2H5OH=1/4 (V/V) at 77 K.
b
c
[(L2)PtCl]
d
Excitation wavelength: 450 nm.

616
D. Qiu et al. / Inorganic Chemistry Communications 13 (2010) 613–617
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.inoche.2010.02.016.
References
[1] W. Lu, B.-X. Mi, M.C.W. Chan, Z. Hui, N. Zhu, S.T. Lee, C.-M. Che, Chem. Commun.
(2002) 206–207.
[2] W. Lu, B.-X. Mi, M.C.W. Chan, Z. Hui, C.-M. Che, N. Zhu, S.-T. Lee, J. Am. Chem. Soc.
126 (2004) 4958–4971.
[3] S.C.F. Kui, I.H.T. Sham, C.C.C. Cheung, C.-W. Ma, B. Yan, N. Zhu, C.-M. Che, W.-F. Fu,
Chem. Eur. J. 13 (2007) 417–435.
[4] B.-P. Yan, C.C.C. Cheung, S.C.F. Kui, V.A.L. Roy, C.-M. Che, S.-J. Xu, Appl. Phys. Lett.
91 (2007) 063508.
[5] B.-P. Yan, C.C.C. Cheung, S.C.F. Kui, H.-F. Xiang, V.A.L. Roy, S.-J. Xu, C.-M. Che, Adv.
Mater. 19 (2007) 3599–3603.
[6] S.-W. Lai, M.C.-W. Chan, T.-C. Cheung, S.-M. Peng, C.-M. Che, Inorg. Chem. 38
(1999) 4046–4055.
[7] W. Lu, M.C.W. Chan, N. Zhu, C.-M. Che, C. Li, Z. Hui, J. Am. Chem. Soc. 126 (2004)
7639–7651.
[8] D.F. Qiu, J. Wu, Z.Y. Xie, Y.X. Cheng, L.X.J. Wang, Organomet. Chem. 694 (2009)
737–746.
Fig. 4. Normalized PL spectra of 4 in dichloromethane solution at 298 K, in an alcoholic
glass (4: 1 EtOH/MeOH) at 77 K and in solid state at 298 K.
[9] 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, Angew. Chem. Int. Ed. 48 (2009) 6664–6666.
[10] Q. Wang, J.Q. Ding, D.G. Ma, Y.X. Cheng, L.X. Wang, F.S. Wang, Adv. Mater. 21
(2009) 2397–2401.
[11] J.Q. Ding, J.H. Lu, Y.X. Cheng, Z.Y. Xie, L.X. Wang, X.B. Jing, F.S. Wang, Adv. Funct.
Mater. 18 (2008) 2754–2762.
[12] R. Clergereaux, I. Séguy, P. Jolinat, J. Farenc, P. Destruel, J. Phys. D: Appl. Phys. 33
(2000) 1947–1952.
respectively. Compared to the ones in CH2Cl2 solution, the large
bathochromic shifts of three emission bands in solid state indicate the
strong effect of molecular aggregation. Ligand HL (3) shows a blue
emission band at 462 nm in CH2Cl2 solution, which is blue-shifted to
446 nm in solid state due to the steric hindrance effect.
For the multi-component complex 4, the selective optical-
stimulation experiments were conducted. Excited at 450 nm, which
was into the Pt(II)-based MLCT absorption band, complex 4 displays a
strong emission at 592 nm with relatively high quantum yield of 0.10
in CH2Cl2 solution at 298 K, and it demonstrates PL maxima at 600,
594 and 590 nm in methanol, ethyl acetate and toluene solutions,
respectively. While a negative solvatochromic effect is observed for its
MLCT absorption wave (λmax at 438, 438, 448 and 470 nm in
methanol, ethyl acetate, CH2Cl2 and toluene solutions respectively),
indicating the Stokes shift increases with strengthening solvent
polarity. At 77 K in alcoholic glass, complex 4 shows well-resolved
vibronic emission profile at 582 nm and 622 nm, respectively (Fig. 4).
In solid state, a red-shifted emission band at 612 nm is observed
arising from the π–π interactions between neighboring [(C^N^N)PtCl]
moieties, which is in accordance with the result of the Crystal
Structure section. The large Stokes shift, solvatochromic effect and
temperature dependence suggest that the emission of complex 4
originates from the spin-forbidden triplet excited state. And its
emission behaviors are almost as same as those of the reported
complex [(L2)PtCl] [8]. Excited at 320 nm, which was into the
carbazole absorption band in the UV region, complex 4 displays two
characteristic emission bands at ca. 350 and 592 nm, respectively. The
higher energy carbazole-based emission band dramatically quenched,
compared with those of 9-(4-Bromobutane)carbazole (1) and the
physical mixture of 9-(4-Bromobutane) carbazole (1) and complex
[(L2)PtCl] (molar ratio=1:1) under the same experimental condition.
The quenching efficiency ([1−(A/A0)]×100(%)) is 85.8%, in which A
and A0 stand for the integrated area from 320 nm to 500 nm in the
emission spectra of complex 4 and 9-(4-Bromobutane)carbazole (1),
respectively. While the intensity of the latter band clearly increased
compared to that of complex [(L2)PtCl]. These results suggest that an
intramolecular energy transfer process from the carbazole unit to the
arylamine-modified [(C^N^N)PtCl] emissive center exists in complex
4. The studies on OLEDs and electrochemistry are in progress and will
be reported in another paper.
[13] G. Inzelt, J. Solid State Electrochem. 7 (2003) 503–510.
[14] J. Natera, L. Otero, L. Sereno, F. Fungo, N.-S. Wang, Y.-M. Tsai, T.-Y. Hwu, K.-T.
Wong, Macromolecules 40 (2007) 4456–4463.
[15] Synthesis of 9-(4-Bromobutane)carbazole (1): To a mixture of KOH (11.2 g) and
nBu4NBr in H2O (20 mL) was added dropwise a solution of carbazole (6.68 g,
40.0 mmol) and 1, 4-dibromobutane (20 mL, 160 mmol) in THF (80 mL), and the
mixture was refluxed for 18 h. After the mixture was cooled to room temperature,
the product was extracted with dichloromethane, washed with distilled water,
and dried over anhydrous sodium sulfate and concentrated. The product mixture
was purified by column chromatography (silica gel, petroleum ether : CH2Cl2 =2:
1 (V/V)). 9-(4-bromobutane)carbazole was obtained as white needle crystal by
recrystallizing from MeOH/Ethyl Acetate solution: 9.5 g (yield: 78.5%). 1H NMR
(300 MHz, CDCl3): δ 8.10 (d, J=7.8 Hz, 2H), 7.49–7.38 (m, 4H), 7.26–7.12 (m,
2H, Ar), 4.38 (t, J=6.9 Hz, 2H), 3.38 (t, J=6.4 Hz, 2H), 2.07 (m, 2H), 1.92 (m,
-CH2-). 13C NMR (75 MHz, CDCl3): δ 140.2, 125.7, 122.9, 120.4, 118.9, 108.5
(Ar), 42.1, 33.1, 30.2, 27.6 (-CH2-). Anal. Calcd for C16H16BrN: C, 63.59; H,
5.34; N, 4.63. Found: C, 63.38; H, 5.25; N, 4.43%.
[16] F. Kröhnke, Synthesis 1 (1976) 1–24.
[17] J.P. Sadighi, R.A. Singer, S.L. Buchwald, J. Am. Chem. Soc. 120 (1998) 213–214.
[18] Synthesis of Ligand HL (3): 4-(p-Bromophenyl)-6-phenyl-2, 2′-bipyridine
(1.94 g, 5.0 mmol), palladium acetate (13.0 mg, 0.06 mmol) and DPEphos
(45.0 mg, 0.08 mmol) were charged into a flask and purged with argon. Aniline
(1.0 mL, 10.7 mmol) was added via syringe, followed by toluene (20 ml). NaOBut
(0.81 g, 8.5 mmol) was added in one portion. The reaction mixture was heated to
80 °C under stirring for 12 h. The solvent was removed by rotary evaporation. The
residue was dissolved in dichloromethane, washed with distilled water, and dried
over anhydrous sodium sulfate and concentrated. The residue was dissolved in
THF (60 mL). NaH (2.5 g, N52%, in mineral oil) was added and purged with argon.
The reaction mixture was stirred for 1 h at room temperature, and then 9-(4-
bromobutane)carbazole (6.04 g, 20.0 mmol) was added dropwise via syringe.
After the solution was refluxed until the conversion was complete (as monitored
by thin layer chromatography), it was cooled to room temperature and poured
into ice–water mixture slowly, extracted with CH2Cl2 until the water phase was
colorless. The combined organic solutions were washed with distilled water,
dried over anhydrous sodium sulfate and concentrated. The crude product was
purified by column chromatography (silica gel, petroleum ether : CH2Cl2 =2:1
(V/V) containing 5% (V) triethylamine). Ligand HL was obtained as pale yellow
crystal by recrystallizing from MeOH/Ethyl Acetate solution: 1.7 g (yield: 54.8%).
1H NMR (300 MHz, CDCl3): δ 8.74–8.66 (m, 3H), 8.20 (d, J=7.2 Hz, 2H), 8.10
(d, J=7.8 Hz, 2H), 7.95 (s, 1H), 7.90 (t, J=7.5 Hz, 1H), 7.69 (d, J=8.7 Hz, 2H),
7.55–7.43 (m, 5H), 7.38–7.30 (m, 5H), 7.23 (t, J=6.9 Hz, 2H), 7.12–7.06 (m, 3H),
6.90 (d, J=8.7 Hz, 2H, Ar), 4.33 (t, J=7.0 Hz, 2H), 3.75 (t, J=7.3 Hz, 2H), 2.04–
1.94 (m, 2H), 1.86–1.76 (m, 2H,-CH2-). Anal. Calcd for C44H36N4: C, 85.13; H,
5.85; N, 9.03. Found: C, 84.92; H, 5.67; N, 8.62%.
[19] Synthesis of Pt(II) complex (4): A mixture of HL (0.32 g, 0.5 mmol), K2PtCl4
(0.21 g, 0.5 mmol) and glacial acetic acid (30 mL) was refluxed for 24 h under a
nitrogen atmosphere in the absence of light. The reaction mixture was then
cooled to room temperature and filtered. The obtained solid was recrystallized
from MeOH/CH2Cl2 solution twice to form the desired product as red crystal:
0.35 g (yield: 82.4%). 1H NMR (300 MHz, CDCl3): δ 8.89 (d, J=5.1 Hz, 1H), 8.68
(d, J=8.1 Hz, 1H), 8.38 (s, 1H), 8.34 (t, J=7.8 Hz, 1H), 8.14 (d, J=7.8 Hz, 2H),
8.12 (d, J=5.4 Hz, 1H), 7.92 (d, J=8.7 Hz, 2H), 7.88 (t, J=6.6 Hz, 1H), 7.75
(d, J=7.5 Hz, 1H), 7.59 (d, J=8.1 Hz, 1H), 7.50–7.36 (m, 5H), 7.21–7.04 (m, 8H),
Acknowledgments
This work is supported by the National Natural Science Foundation
of China (No. 50673088), Science Fund for Creative Research Groups
(No. 20621401) and 973 Project (2009CB623600).

D. Qiu et al. / Inorganic Chemistry Communications 13 (2010) 613–617
617
6.85 (d, J=8.7 Hz, 2H, Ar), 4.42 (t, J=6.9 Hz, 2H), 3.80 (t, J=6.9 Hz, 2H), 1.88
(m, 2H), 1.72 (m, 2H,-CH2-). Anal. Calcd for C44H35ClN4Pt: C, 62.15; H, 4.15; N,
6.59. Found: C, 61.67; H, 4.11; N, 6.28%.
[21] S.-W. Lai, M.C.-W. Chan, K.-K. Cheung, C.-M. Che, Organometallics 18 (1999)
3327–3336.
[22] J.H.K. Yip, Suwarno, J.J. Vittal, Inorg. Chem. 39 (2000) 3537–3543.
[23] S.-W. Lai, H.-W. Lam, W. Lu, K.-K. Cheung, C.-M. Che, Organometallics 21 (2002)
226–234.
[24] A. Hofmann, L. Dahlenburg, R. van Eldik, Inorg. Chem. 42 (2003) 6528–6538.
[25] G.M. Sheldrick, SHELXL 97, Program for Crystal Structure Refinement, University
of Göttingen, Göttingen, Germany, 1997.
[26] G.M. Sheldrick, SHELXL 97, Program for Crystal Structure Solution, University of
Göttingen, Göttingen, Germany, 1997.
[20] Diffraction data was collected on a Bruker SMART APEX II CCD diffractometer
equipped with a graphite-monochromated Mo-Kα radiation (λ=0.71073 Å) at
296(2) K using a Φ–ω scan mode in the range of 2.38≤θ≤25.00°. A total of 17497
reflections including 6130 unique ones were collected, of which 6101 were
observed [IN2σ (I)] and used in structure solution. 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.