Synthesis, crystal structure, photoluminescence and theoretical studies of a series of copper(I) compounds based on imidazole derivatives

Article abstract of DOI:10.1016/j.ica.2012.07.020

Two mononuclear and one binuclear Cu(I) complexes that contain imidazole derivative ligands including 2-(2′-pyridyl)imidazole (L1), 2-(2′-pyridyl)benzimidazole(L2), and 2,6-bis (benzimidazol-2yl)-pyridine (L3) were synthesized. The formulas of these complexes are [CuL1(PPh ₃)₂][BF₄] (1), [CuL2(PPh₃) ₂][BF₄] (2), [Cu₂(L3)₂(PPh ₃)₂][BF₄]₂ (3), respectively. The crystal structures of complexes 1-3 have been determined by single-crystal X-ray diffraction analyses. The Cu(I) ions in the complexes have a distorted tetrahedral geometry. Photophysical properties of complexes 1-3 were systematically studied. These complexes maximum emission are mainly concentrated in the 623-680 nm. An electroluminescent (EL) device using 2 as the emitter was fabricated. The device produced a red emission which matches with the PL spectrum. However, the EL device of 2 is unfavorable. The absorption properties of complexes 1 and 2 were theoretically analyzed by time-dependent density functional theory (DFT).The calculated results are in good agreement with the experimental data.

Full text of DOI:10.1016/j.ica.2012.07.020

Inorganica Chimica Acta 394 (2013) 15–20
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, crystal structure, photoluminescence and theoretical studies of a series
of copper(I) compounds based on imidazole derivatives
b
Tingting Hou a,b, Jiangyu Bian a, Xiangru Yue b, Shumei Yue a, , Jianfang Ma
⇑
a College of Chemistry, Changchun Normal University, Changchun 130032, PR China
b Faculty of Chemistry, Northeast Normal University, Changchun 130024, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Two mononuclear and one binuclear Cu(I) complexes that contain imidazole derivative ligands including
2-(20-pyridyl)imidazole (L1), 2-(20-pyridyl)benzimidazole(L2), and 2,6-bis (benzimidazol-2yl)-pyridine
(L3) were synthesized. The formulas of these complexes are [CuL1(PPh3)2][BF4] (1), [CuL2(PPh3)2][BF4]
(2), [Cu2(L3)2(PPh3)2][BF4]2 (3), respectively. The crystal structures of complexes 1–3 have been deter-
mined by single-crystal X-ray diffraction analyses. The Cu(I) ions in the complexes have a distorted tet-
rahedral geometry. Photophysical properties of complexes 1–3 were systematically studied. These
complexes maximum emission are mainly concentrated in the 623–680 nm. An electroluminescent
(EL) device using 2 as the emitter was fabricated. The device produced a red emission which matches
with the PL spectrum. However, the EL device of 2 is unfavorable. The absorption properties of complexes
1 and 2 were theoretically analyzed by time-dependent density functional theory (DFT).The calculated
results are in good agreement with the experimental data.
Received 25 April 2012
Received in revised form 17 July 2012
Accepted 21 July 2012
Available online 31 July 2012
Keywords:
Cu(I) complexes
Crystal structure
UV–Vis spectrum
Fluorescence spectrum
DFT
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
sized three novel Cu(I) complexes. We obtained the crystal struc-
ture of [CuL1(PPh3)2][BF4]2 (1), [CuL2(PPh3)2][BF4]2 (2), [Cu2(L3)2
Phosphorescent materials based on heavy metal complexes have
great potential applications, such as light-emitting devices, solar
cells, or sensors/probes [1–7]. The phosphorescence compounds
of the earlier studies focused on noble Ir(III), Pt-(II), and Ru(II)com-
plexes [8–12]. In recent years, phosphorescent Cu(I) complexes re-
ceive much attention due to relatively abundant resource and
nontoxic property, which make these complexes very applicable
in solar energy conversion, biological probing, and organic light-
emitting devices (OLEDs) [13–18]. Zn and Cd of imidazole com-
plexes as Blue light emitting materials have been illustrated by
our research groups [19,20]. However, Cu(I) of imidazole complexes
has rarely been reported. A series of Cu(I) complexes with different
phosphorous/phenanthroline ligands and their electro-lumines-
cence (EL) performances have been reported by Wang and co-work-
ers [21]. Li and co-workers reported electroluminescent colors can
be tuned ranging from green-yellow to orange-red region using
Cu(I) complexes as doped material [18]. Li and co-workers reported
a series of Cu(I) complexes which exhibit a maximum brightness of
4483 cd/m2 and a peak efficiency of 3.4 cd/A [22]. Heteroleptic Cu(I)
complexes comprising imidazole derivatives and triphenylphos-
phine (PPh3) are promising, because they are capable of producing
MLCT phosphorescent emission [23,24]. In this work, we synthe-
(PPh3)2][BF4]2 (3). We reported the preparation, crystal structure,
UV–Vis spectrum, fluorescence spectrum and DFT calculation of
complexes.
2. Experimental
2.1. Materials and methods
Triphenylphosphine (referred as PPh3), pyridine-2-aldehye and
pyridine-2, 6-dicarboxylic acid were purchased from Aldrich and
used without further purification. The other reagents and com-
plexes were synthesized accord to procedures. UV–Vis spectrums
of samples were recorded on a TU-1901 spectrometer. Fluores-
cence spectra of samples were recorded on a RF-5301 spectrome-
ter. Elemental analyses were performed on a Perkin-Elmer 240c
analyzer. 1H NMR spectra of samples were recorded on a Brucker
AC-80 spectrometer. IR spectra of samples were recorded on a
MAGNA-560 spectrometer.
2.2. Synthesis of [CuL1(PPh3)2][BF4]
2.2.1. Synthesis of [CuL1(PPh3)2][BF4] (1)
In 10 mL of dichloromethane, 0.525 g (0.002 mol) PPh3 and
0.314 g (0.001 mol) [Cu(CH3CN)4]BF4 were dissolved and was stir-
red for 1 h at room temperature. After a dichloromethane solution
⇑
Corresponding author. Tel.: +86 431 86168094.
E-mail address: yuesm458@nenu.edu.cn (S. Yue).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.07.020

16
T. Hou et al. / Inorganica Chimica Acta 394 (2013) 15–20
Fig. 1a. Molecule structure of complex 1.
(5 mL) of 0.135 g (0.001 mol) L1 was added, the solvent was stirred
for another 4 h to give an orange solution. The solution was then
filtered and evaporated to dryness. The residue was dissolved in
dichloromethane and diffusion of methanol vapor into its concen-
trated solution gave orange crystals of 1 after 6 days (0.76 g, 78%).
Anal. Calc. for C44H36 BCuF4N3OP2: C, 63.23; H, 4.31; N, 5.03.
Found: C, 63.24; H,4.36; N, 5.05%. IR (cmꢀ1): IR (cmꢀ1): 1545,
1538, 1347, 765, 779. 1H NMR (300 Hz, CDCl3, 25 °C): d 8.60(d,
2H, J = 8.0 Hz), 8.4 (d, 2H, J = 8.0 Hz), 8.01–7.75 (m, 20H), 7.51–
7.36 (m, 12H). 31P NMR d + 1.71 (s).
2.3. Synthesis of [CuL2(PPh3)2][BF4]
2.3.1. Synthesis of [CuL2(PPh3)2][BF4] (2)
In 10 mL of dichloromethane, 0.525 g (0.002 mol) PPh3 and
0.314 g (0.001 mol) [Cu(CH3CN)4]BF4 were dissolved and was stir-
red for 1 h at room temperature. After a dichloromethane solution
(5 mL) of 0.195 g (0.001 mol) L2 was added, the solvent was stirred
for another 4 h to give an orange solution. The solution was then
filtered and evaporated to dryness. The residue was dissolved in
dichloromethane and diffusion of methanol vapor into its concen-
trated solution gave orange crystals of 2 after 7 days (0.77 g, 74%).
Fig. 1b. Molecule structure of complex 2.

T. Hou et al. / Inorganica Chimica Acta 394 (2013) 15–20
17
Fig. 1c. Molecule structure of complex 3.
Anal. Calc. for C48H37BCuF4N3P2: C, 66.35; H, 4.26; N, 4.84. Found:
2.4. Synthesis of [Cu2(L3)2(PPh3)2][BF4]2
C, 66.34; H,4.30; N, 4.82%. IR (cmꢀ1): 1610, 1253, 1290, 2085,
2097. 1H NMR (300 Hz, CDCl3, 25 °C): d 8.30 (d, 2H, J = 8.0 Hz),
8.05 (1H, s), 7.82(1H, t), 7.26 (d, 2H,), 8.01–7.75 (m, 20H), 7.51–
7.36 (m, 12H). 31P NMR d + 1.70 (s).
2.4.1. Synthesis of [Cu2(L3)2(PPh3)2][BF4]2 (3)
In 10 mL of dichloromethane, 0.525 g (0.002 mol) PPh3 and
0.314 g (0.001 mol) [Cu(CH3CN)4]BF4 were dissolved and was stir-
red for 1 h at room temperature. After a dichloromethane solution
Table 1
Crystal data and structure refinement for complexes 1–3.
Complex 1
Complex 2
Complex 3
Chemical formula
Temperature (K)
Wavelength (A)
Formula weight
Space group
a (Å)
C
44H36BCuF4N3OP2
C48H37BCuF4N3P2
293(2)
0.71069
C51H61B2Cu2F8N10O2P2
293(2)
0.71069
1208.74
C2/c
293(2)
0.71069
835.05
P1
10.086(5)
868.10
ꢀ
ꢀ
P1
11.528(5)
12.800(5)
22.2550(11)
14.9990(7)
b (Å)
14.382(5)
c (Å)
15.053(5)
76.546(5)
16.365(5)
82.421(5)
21.6820(10)
90.00
a
(°)
b (°)
77.955(5)
85.186(5)
2075.4(14)
75.186(5)
66.105(5)
2133.3(14)
99.7530(10)
90.00
7132.9(6)
c
(°)
V (Å3)
Z
2
2
4
Dcalc (mg/m3)
1.336
0.658
858
1.351
0.642
892
1.126
0.700
2492
Absorption coefficient (mmꢀ1
F(000)
)
Crystal size (mm)
Theta range for data collection (°)
h
k
0.24 ꢁ 0.25 ꢁ 0.26
1.42 to 28.37
ꢀ7 6 h 6 13
ꢀ18 6 k 6 18
ꢀ20 6 l 6 19
12993/9610
[R(int) = 0.0206]
28.37(92.5%)
Semi-empirical from equivalents
Full-matrix least-squares on F2
9610/0/235
1.049
0.24 ꢁ 0.25 ꢁ 0.26
1.29 to 25.00
ꢀ13 6 h 6 7
ꢀ15 6 k 6 14
ꢀ19 6 l 6 18
10878/7476
[R(int) = 0.0201]
25.00(99.3 %)
Semi-empirical from equivalents
Full-matrix least-squares on F2
7476/0/243
1.106
0.23 ꢁ 0.21 ꢁ 0.18
1.64 to 28.32
ꢀ28 6 h 6 25
ꢀ15 6 k 6 20
ꢀ28 6 l 6 25
22101/8680
[R(int) = 0.0275]
25.00(99.9 %)
Semi-empirical from equivalents
Full-matrix least-squares on F2
8680/12/473
1.028
l
Reflections collected/unique
Completeness to h
Absorption correction
Refinement method
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R1, wR2 [I > 2
Final R1, wR2 (all data)
qmin (e Aꢀ3
r
(I)]
0.0947, 0.2673
0.1476, 0.3164
1.130, ꢀ0.846
0.0960, 0.2675
0.1070, 0.2808
2.442, ꢀ1.178
0.0470, 0.1291
0.0742, 0.1470
0.806, ꢀ0.591
D
qmax
,
D
)

18
T. Hou et al. / Inorganica Chimica Acta 394 (2013) 15–20
(5 mL) of 0.287 g (0.001 mol) L3 was added, the solvent was stirred
for another 4 h to give an orange solution. The solution was then
filtered and evaporated to dryness. The residue was dissolved in
dichloromethane and diffusion of methanol vapor into its concen-
trated solution gave orange crystals of 3 after 5 days (0.9 g, 79%).
Anal. Calc. for C51H61B2Cu2F8N10O2P2: C, 50.63; H, 5.04; N, 11.58.
Found: C, 50.62; H,5.03; N, 11.57%. IR (cmꢀ1): 1620, 1510, 1456,
762, 685. 1H NMR (300 Hz, CDCl3, 25 °C):
d 9.36 (d, 2H,
J = 8.0 Hz), 8.05 (1H, s), 7.82 (1H, t), 7.26 (d, 2H,), 8.01–7.75 (m,
20H), 7.51–7.36 (m, 12H). 31P NMR d + 1.70 (s).
3. Results and discussion
3.1. Description of crystal structures
The crystal structure of complexes 1–3 are shown in Figs. 1a–1c.
The Cu (I) ions in the complexes have a distorted tetrahedral geom-
etry. Compound 1 and 2 belong to the triclinic space group P1, while
compound 3 belongs to the monoclinic space group C2/c. The BF4 an-
ions in all compounds were found to display disordering and were
refined successfully. In complex 1, there is a distinct difference be-
tween theCu–N bond lengths: the Cu(1)–N (3) (pyridyl) bond length
Fig. 2b. UV–Vis spectra of complexes 1–3 in CH2Cl2 with
a concentration of
ꢀ
1 ꢁ 10ꢀ5 mol/L (1 is complex 1, 2 is complex 2, 3 is complex 3).
Table 2
Selected bond lengths (Å) and angles (°C).
Compound 1
Cu(1)–N(1)
Cu(1)–N(3)
Cu(1)–P(1)
Cu(1)–P(2)
2.072(5)
2.113(5)
2.2500(17)
2.2640(18)
N(1)–Cu(1)–N(3)
N(1)–Cu(1)–P(1)
N(3)–Cu(1)–P(1)
N(1)–Cu(1)–P(2)
N(3)–Cu(1)–P(2)
P(1)–Cu(1)–P(2)
80.0(2)
118.02(15)
107.21(14)
105.98(15)
109.32(14)
126.40(6)
Compound 2
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–P(2)
Cu(1)–P(1)
2.099(5)
2.109(5)
2.2645(16)
2.2670(17)
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–P(2)
N(2)–Cu(1)–P(2)
N(1)–Cu(1)–P(1)
N(2)–Cu(1)–P(1)
P(2)–Cu(1)–P(1)
80.09(18)
108.21(13)
112.10(13)
109.91(14)
109.91(13)
126.76(6)
Compound 3
Cu(1)–N(2)
Cu(1)–N(4)
Cu(1)–N(3)
Cu(1)–P(1)
2.059(2)
2.111(2)
2.167(2)
2.2084(7)
N(2)–Cu(1)–N(4)
N(2)–Cu(1)–N(3)
N(4)–Cu(1)–N(3)
N(2)–Cu(1)–P(1)
N(4)–Cu(1)–P(1)
N(3)–Cu(1)–P(1)
96.07(9)
118.24(8)
78.32(9)
124.12(6)
114.88(7)
113.08(6)
Fig. 3. Emission spectrum of complexes 1–3 in CH2Cl2 with a concentration of
1 ꢁ 10ꢀ5 mol/L (1 is complex 1, 2 is complex 2, 3 is complex 3).
Fig. 4. The PL spectrum of 2 and EL spectra of the OLEDs based on 2 (2 is complex
2).
Fig. 2a. UV–Vis spectra of ligands in CH2Cl2 with a concentration of 1 ꢁ 10ꢀ5 mol/L.

T. Hou et al. / Inorganica Chimica Acta 394 (2013) 15–20
19
Fig. 5. Simulation absorption spectrum of complexes 1–2 (1 is complex 1, 2 is
complex 2).
Fig. 7. Molecular orbital of complex 2.
3.2. Photophysical properties
Fig. 2a shows the UV–Vis absorption spectra of ligand L1, ligand
L2, ligand L3 in dichloromethane. The free ligands L1, L2 and L3
show two absorption peaks at kmax ꢂ 230 and 300 nm, which are
probably assigned to intraligand
p–
p⁄ transitions. We found that
the increase in conjugation with the nitrogen ligands, the maxi-
mum absorption has obvious red shift. Fig. 2b shows the UV–Vis
absorption spectra of complexes 1–3 in dichloromethane. Com-
pared with the ligands, complexes have
a little red shift.
Complexes 1–3 have multiple absorption peaks in the 220–
300 nm region that can be attributed to an admixture of the intral-
igand
p–
p⁄ (IL) transitions of PPh3 and the imidazole derivatives
[22]. These complexes have wide and weak absorption bands in
the low-energy absorption region of 300–360 nm long-wavelength
range, which are tentatively assigned to the metal to ligand
charge-transfer (MLCT) transitions according to the previous re-
ports [17,23].
Fig. 3 exhibits the emission spectra of complexes 1–3 in dichlo-
romethane. The MLCT transitions bands with the maximum value
of these complexes are mainly concentrated in the 623–680 nm.
The strongest emission peak of Complex 1, Complex 2 and Com-
plex 3 are 623.0 nm, 626.0 nm and 679.0 nm, respectively [23].
We found that the increase in conjugation with the nitrogen li-
gands, the emission spectra has obvious red shift.
Fig. 6. Molecular orbital of complex 1.
(2.113(5) Å) is much longer than that of Cu (1)–N(1), (imidazolyl,
2.072(5) Å), indicating that the imidazolyl nitrogen atom is a stron-
ger donor than that of the pyridyl ring. The same trend was also ob-
served for the structures of 2 and 3 (see Table 2). Nevertheless, the
observed N–Cu–N bond angles in compound 1 and 2 are similar to
literature ones [17,21]. In complex 3, the central two Cu(I) ions have
also an approximately tetrahedral geometry with two terminal PPh3
ligands and two 2,6-bis(benzimidazol-2yl)-pyridine chelate. Com-
plex 3 is a novel binuclear with N–Cu–N angles around 78.32–
118.24°. The crystallographic data are given in Table 1. Selected
bond lengths and angles for complexes 1–3 are listed in Table 2.
3.3. EL properties
Complex 2 was selected as a representative example for the
investigation of electroluminescent properties of the Cu(I) com-
plexes. The OLEDs utilizing complex 2 as dopants in the CBP emis-
sive layer was fabricated with the structure of MoO3/NPB/CBP:
compound 2/TPBi.
Fig. 4 shows the PL spectrum of 2 and EL spectra for the devices
based on 2 at the applied voltage of 12 V with a doping concentra-
tion of 6 wt.%. The device produced a red emission which matches

20
T. Hou et al. / Inorganica Chimica Acta 394 (2013) 15–20
with the PL spectrum. However, the EL device of 2 is unfavorable
As noted by Wang and co-workers [21], the POP ligand, POP = -
bis[2-(diphenylphosphino)phenyl]ether, is much better than PPh3
ligand in Cu(I) complexes due to its increased quantum efficiency
and the shortened decay lifetime. Therefore, to improve the perfor-
mance of the EL devices, a modification on the ligand will be car-
ried in our laboratory in the future.
4. Conclusions
In this paper, we report a series of Cu(I) complexes based on
three imidazole derivatives and triphenylphosphine (PPh3). We
studied their molecular structure, electronic structure, photophys-
ical properties and the DFT. Single crystal diffraction experiments
show that the copper complex objects are distorted tetrahedral
structure. The calculated results are in good agreement with the
experimental data.
3.4. TD-DFT
The absorption spectra of the system are computed by using
TD-DFT (CAM-B3LYP) method, the Lanl2dz pseudo-potential basis
sets is employed for metal atoms, and for the other atoms, the 6-
311G⁄⁄ basis set is used. The calculated results are in good agree-
ment with the experimental data.
The simulation absorption spectrum for the two complexes is
shown in Fig. 5. Fig. 6 is molecular orbital of complex 1. The two
calculated maximum absorption peak wavelength for complex 1
are 193.65 and 235.53 nm, close to the 228 and 258 nm for exper-
imental, which correspond to the HOMOꢀ3 ? LUMO+7 and HOMO-
ꢀ1 ? LUMO+7 transition, respectively. According to the analysis of
Acknowledgements
The authors gratefully acknowledge the financial support by the
Ministry of Education of the People’s Republic of China (No.
208034) and Jilin Provincial Department of Education project
(Nos. 2009-203 and 2011-192).
References
[1] N. Armaroli, G. Accorsi, F. Cardinali, A. Listorti, Top. Curr. Chem. 280 (2007) 69.
[2] A.P. de Silva, D.B. Fox, T.S. Moody, S.M. Weir, Pure Appl. Chem. 73 (2001) 503.
[3] G. Accorsi, A. Listorti, K. Yoosaf, N. Armaroli, Chem. Rev. 38 (2009) 1690.
[4] P.J. Walsh, N.J. Lundin, K.C. Gordon, J.Y. Kim, C.H. Lee, Opt. Mater. 31 (2009) 1525.
[5] L. Chassot, Inorg. Chem. 23 (1984) 4249.
[6] D. Sandrini, M. Maestri, V. Balzani, L. Chassot, A. von Zelewsky, J. Am. Chem.
Soc. 109 (1987) 3107.
[7] A. Vogler, H. Kunkely, Coord. Chem. Rev. 177 (1998) 81.
[8] H. Xia, C. Zhang, S. Qiu, P. Lu, J. Zhang, Y. Ma, Appl. Phys. Lett. 84 (2004) 290.
[9] X. Gong, M.R. Robinson, J.C. Ostrowski, D. Moses, G.C. Bazan, A.J. Heeger, Adv.
Mater. 14 (2002) 581.
its front molecular orbit, the HOMO is a
gand and dz for metal atom, the HOMOꢀ1 is a
p
bonding orbit for li-
ꢀ3
2
p
bonding orbit
for ligand and dyz for metal atom, while the LUMO+7 is a
p
p
anti-
2
2
bonding orbit of ligand and dx
for metal atom. So, the
?
p⁄
ꢀy
transition between ligand and metal atom is the main source of
the maximum absorption peak of complex 1.
For complex 2, the two calculated maximum absorption peak
wavelength are 187.77 and 232.82 nm, close to the 229 and
257 nm for experimental in the high-energy absorption region.
The calculated maximum absorption peak wavelength which cor-
responds to the HOMO ? LUMO transition is 334.76 nm, close to
the 326 nm for experimental in the low-energy absorption region.
Fig. 7 is molecular orbital of complex 2. The absorption peak at
187.77 nm corresponds to the HOMO ? LUMO+26 transition. As
can be seen from the analysis of its front molecular orbit, the
[10] X. Gong, J.C. Ostrowski, G.C. Bazan, D. Moses, A.J. Heeger, Appl. Phys. Lett. 81
(2002) 3711.
[11] S. Welter, K. Brunner, J.W. Hofstraat, L. De Cola, Nature 421 (2003) 54.
[12] Y.-L. Tung, S.-W. Lee, Y. Chi, L.-S. Chen, C.-F. Shu, F.-I. Wu, A.J. Carty, P.-T. Chou,
S.-M. Peng, G.-H. Lee, Adv. Mater. 17 (2005) 1059.
[13] D.G. Cuttell, S.M. Kuang, P.E. Fanwick, D.R. McMillin, R.A. Walton, J. Am. Chem.
Soc. 124 (2002) 6.
[14] S.M. Kuang, D.G. Cuttell, D.R. McMillin, P.E. Fanwick, R.A. Walton, Inorg. Chem.
41 (2002) 3313.
[15] A. Tsuboyama, K. Kuge, M. Furugori, S. Okada, M. Hoshino, K. Ueno, Inorg.
Chem. 46 (2007) 1992.
[16] T. McCormick, W.L. Jia, S. Wang, Inorg. Chem. 45 (2006) 147.
[17] W.-L. Jia, T. McCormick, Y. Tao, J.-P. Lu, S.N. Wang, Inorg. Chem. 44 (2005) 5706.
[18] G. Che, Z. Su, W. Li, B. Chu, M. Li, Z. Hu, Z. Zhang, Appl. Phys. Lett. 89 (2006)
103511.
[19] S.M. Yue, N. Li, J.Y. Bian, T.T. Hou, J.F. Ma, Synth. Metals. 162 (2012) 247.
[20] S.-M. Yue, Z.-M. Su, J.-F. Ma, Y. Liao, Y.-H. Kan, H.-J. Zhang, Chin. J. Struct. Chem.
22 (2003) 174.
[21] Q. Zhang, Q. Zhou, Y. Cheng, L. Wang, D. Ma, X. Jing, F. Wang, Adv. Mater. 16
(2004) 432.
HOMO is a
LUMO+26 is a
p bonding orbit for ligand and dyz for metal atom, the
2
2
p
anti-bonding orbit of ligand and dx
for metal
ꢀy
atom. The absorption peak at 232.82 nm corresponds to the
HOMOꢀ1 ? LUMO+3 transition. As can be seen from the analysis
of its front molecular orbit, the HOMOꢀ1 is a
gand and dxy for metal atom, the LUMO+3 is a
of ligand and dyz for metal atom. So, the maximum absorption peak
p
bonding orbit for li-
p
anti-bonding orbit
[22] Z.J. Si, J. Li, B. Li, S.Y. Liu, J. Lumin. 129 (2009) 181.
[23] L.M. Zhang, S.M. Yue, B. Li, D. Fan, Inorg. Chim. Acta 384 (2012) 225.
[24] S.-B. Zhao, T. McCormick, S.N. Wang, Inorg. Chem. 46 (2007) 10965.
of complex 2, same as complex 1, is attributed to the
sition between ligand and metal atom.
p ?
p⁄ tran-