Synthesis and crystal structure of photoluminescent copper(I)-phosphine complexes with oxygen and nitrogen donor ligands

Article abstract of DOI:10.1016/S1387-7003(03)00015-7

Two mononuclear copper(I) complexes, [Cu(PPh₃)₂(oxine)](BF₄) (1) and [Cu(PPh₃)₂(Quin)](BF₄) (2), have been prepared and their structures determined by X-ray crystallography. In complex 1, the copper(I) is coordinated by two PPh₃ groups and one neutral bidentate oxine (8-hydroxyquinoline) in a distorted tetrahedral geometry. The copper(I) atom in complex 2 is surrounded by two PPh₃ and one quinoline (quin) to complete a three-coordinate environment. At room temperature in the solid state both complexes exhibit photoluminescence originated from the intraligand (oxine or quinoline) triplet enhanced by copper coordination. This may provide a new entry to develop new kinds of photoemissive materials.

Full text of DOI:10.1016/S1387-7003(03)00015-7

Inorganic Chemistry Communications 6 (2003) 469–473
www.elsevier.com/locate/inoche
Synthesis and crystal structure of photoluminescent
copper(I)–phosphine complexes with oxygen and nitrogen
donor ligands
a,
a
a
a
b
b
Dan Li *, Rong-Zhen Li , Zheng Ni , Zhi-Yu Qi , Xiao-Long Feng , Ji-Wen Cai
a
Department of Chemistry, Shantou University, Shantou, Guangdong 515063, PR China
b
Instrumentation Analysis and Research Center & School of Chemistry and Chemical Engineering, Sun Yat-Sen (Zhongsan) University,
Guangzhou 510275, PR China
Received 20 September 2002; accepted 24 December 2002
Abstract
Two mononuclear copper(I) complexes, ½CuðPPh3Þ2ðoxineފðBF4Þ (1) and ½CuðPPh3Þ2ðQuinފðBF4Þ (2), have been prepared and
their structures determined by X-ray crystallography. In complex 1, the copper(I) is coordinated by two PPh3 groups and one
neutral bidentate oxine (8-hydroxyquinoline) in a distorted tetrahedral geometry. The copper(I) atom in complex 2 is surrounded by
two PPh3 and one quinoline (quin) to complete a three-coordinate environment. At room temperature in the solid state both
complexes exhibit photoluminescence originated from the intraligand (oxine or quinoline) triplet enhanced by copper coordination.
This may provide a new entry to develop new kinds of photoemissive materials.
Ó 2003 Elsevier Science B.V. All rights reserved.
Keywords: Copper(I) complex; Crystal structure; Oxine; Quinoline; Triphenylphosphine; Photoluminescence
1. Introduction
cles [7], we describe in this paper the synthesis and
characterization of a new photoluminescent Cu(I) com-
plex containing a N, O-donor ligand oxine, as well as a
complex with N-donor heterocycle quinoline for com-
parison. Both complexes were rendered air stable by in-
troducing the ancillary PPh3 ligand to stabilize the copper
+1 state. Being built in a simple fashion, the complexes
may act potentially as photoluminescent materials.
The synthesis and structure of Cu(I) complexes have
been widely explored for the versatility of their coordi-
nation geometries [1]. Such studies have covered differ-
ent areas and have been related, for example, with
structural problems in copper complexes, catalytic ac-
tivities, biochemical systems and functional materials
[2,3]. Structural studies of mononuclear Cu(I) complexes
with N-donor and P-donor ligands have shown that
three-coordinate copper(I) is relatively rare whereas
four-coordinate geometry is the norm [4]. Some of the
Cu(I) complexes have been found to be photolumines-
cent [5]. As Cu(I) is an unstable oxidation state, only a
few complexes with O-donor ligands were synthesized
and structurally characterized [6].
2. Experimental
2.1. General
All the reactions were carried out under N2 atmo-
sphere. The chemicals and reagents were obtained
commercially and used without further purification. The
Cu(I) starting materials, ½CuðMeCNÞ2ðPPh3Þ2ŠðBF4Þ [8],
was prepared by addition of PPh3 to fresh prepared
½CuðMeCNÞ4ŠðBF4Þ [9] in CH2Cl2.
Following our interest on coordination and photolu-
minescence properties of Cu(I) with N-donor heterocy-
* Corresponding author. Tel.: +86-754-290-3154; fax: +86-754-251-
Infrared spectra were recorded in the range of
4000–400 cmÀ1 on a Nicolet Magna 750 spectrometer.
0505.
E-mail address: dli@stu.edu.cn (D. Li).
1387-7003/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S1387-7003(03)00015-7

470
D. Li et al. / Inorganic Chemistry Communications 6 (2003) 469–473
Table 1
Data collection and structure refinement parameters of 1 and 2
Elemental analyses were carried out using a Perkin–El-
mer 240C instrument. Ultraviolet and photolumines-
1
2
cence analyses were performed on
a
UV-1100
spectrometer and a Perkin–Elmer LS 55 luminescence
spectrometer, respectively.
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C45H37BCuF4NOP2
820.05
293(2)
C45H37BCuF4NP2
804.05
293(2)
Monoclinic
P21=n
Monoclinic
P21=c
2.2. Syntheses
ꢀ
a (A)
11.372(3)
22.171(5)
16.038(4)
97.942(5)
19.445(5)
11.878(3)
17.637(4)
94.009(4)
2.2.1. ½CuðPPh3Þ ðoxineފðBF4Þ ð1Þ
ꢀ
b (A)
2
ꢀ
c (A)
Oxine (8-hydroxyquinoline, 145 mg, 1 mmol) was
added to a solution of ½CuðMeCNÞ2ðPPh3Þ2ŠðBF4Þ (378
mg, 0.5 mmol) in CHCl3 (15 ml) under N2 to give a light
yellow–green solution. The solution was heated and
stirred for 24 h. After reduction in volume, diethyl ether
was added to yield a yellow precipitate. The solid was
filtered off, dried and dissolved in a minimum volume of
CHCl3. Diffusion of diethyl ether gave a crop of dark
yellow rod-like crystals after 2 days. Anal. Calcd. for
C45H37BCuF4NOP2: C, 65.91; H, 4.52; N, 1.71; Found:
b ð°Þ
ꢀ3
V ðA Þ
4005.0(16)
4
1.360
4063.5(16)
4
1.314
Z
Dcalc ðg cmÀ3
Þ
F (0 0 0)
l ðmmÀ1
1688
0.680
1656
0.667
Þ
h range (°)
Crystal size (mm)
Reflections collected/ 21908/8147 (0.0255)
2.56–26.37
0:43 Â 0:20 Â 0:10
4.08–25.03
0:43 Â 0:28 Â 0:23
19882/7138
(0.0351)
1.041
unique (Rint
GoF on F 2
Final R1,
)
1.020
0.0387, 0.1035
C, 65.74; H, 4.60; N, 1.75. IR (KBr pellets), m=cmÀ1
:
0.0416, 0.1069
516s, 694vs, 744vs, 1435vs, 1478s, (PPh3); 1096vs (BFÀ4 );
1378m, 1518m (oxine). UV, kmax=nmðe= Â 104 dm3
molÀ1 cmÀ1Þ: 241(6.02), 261(2.69).
wR2½I > 2rðIފ
Oxine is a bidentate ligand with O- and N-donor atoms
for coordinating to metals. Direct reaction between ox-
ine and ½CuðMeCNÞ2ðPPh3Þ2ŠðBF4Þ in CHCl3 yields 1, in
which the oxine coordinates to Cu(I) as a neutral mol-
ecule while its hydroxyl group remains unchanged, as
expected. Elemental analysis has confirmed that the ex-
istence of the BFÀ4 anion to balance copper +1 state. The
strong IR absorption peak at 1096 cmÀ1 also indicates
the presence of the BFÀ4 anion [10]. This contrasts with
the reported Cu(I) complex ½Cuð2Me-quinÞ ðPPh3Þ2Š
(where 2Me-quin represented 2-methylquinolin-8-olate),
in which the hydroxyl group has been deprotonated [11].
Another neutral complex with deprotoned oxine was
found in ½CuðoxineÞðPPh3Þ2Š which was synthesized by
the reaction between ½CuðacacÞ ðPPh3Þ2Š (acac ¼ acetyl-
acetonate) and oxine in dichloromethane and charac-
terized by elemental analysis [8].
2.2.2. ½CuðPPh3Þ ðQuinފðBF4Þ ð2Þ
2
Quinoline (128 mg, 1 mmol) was added to a solution
of ½CuðMeCNÞ2ðPPh3Þ2ŠðBF4Þ (378 mg, 0.5 mmol) in
CHCl3 (15 ml) under N2. The light yellow solution was
stirred for 20 h. After reduction in volume, diethyl ether
was added to yield a yellow precipitate. The solid was
filtered off, dried and dissolved in a minimum volume of
CHCl3. Diffusion of diethyl ether gave a crop of light
yellow block-like crystals after 3 days. Anal. Calcd. for
C45H37BCuF4NP2: C, 67.22; H, 4.61; N, 1.74; Found: C,
67.54; H, 4.81; N, 1.62. IR (KBr pellets), m=cmÀ1: 518s,
696vs, 743vs, 1435vs, 1480s, (PPh3); 1094vs (BFÀ4 );
1312m, 1507m (quin). UV, kmax=nmðe= Â 104 dm3
molÀ1 cmÀ1Þ: 265(2.54), 313(0.44).
2.3. X-ray data collection
Addition of solid quinoline to a chloroform solution
of ½CuðMeCNÞ4ðPPh3Þ2ŠðBF4Þ afforded a light yellow
solution complex 2. The characteristic absorptions of
ligands triphenylphosphine and quinoline as well as the
anion BFÀ4 have been observed in the IR spectrum.
Intensity measurements were collected on a Brucker
SMART CCD diffractometer with graphite-monochro-
ꢀ
mated Mo-Ka radiation (k ¼ 0:71073 A). All calcula-
tions were performed using the SHELXTL package. The
structures were solved by direct methods and refined by
full-matrix least squares. The detailed crystal data and
structure refinement parameters are given in Table 1.
3.2. Crystal structures
X-ray crystallography has established that the crystal
structure of complex
1
consists of monomeric
þ
3. Results and discussion
½CuðPPh3Þ2ðoxineފ cation (Fig. 1). Selected bond dis-
tances and angles are listed in Table 2. The oxine ligand
is chelated to the copper ion through its N-donor and O-
donor sites forming a five-membered chelating ring. The
distorted four-coordinate geometry of Cu(I) is com-
pleted by two triphenylphosphine ligands, which is
3.1. Synthesis
By introducing the PPh3 ligand to stabilize the cop-
per(I) state, we obtained two air stable Cu(I) complexes.

D. Li et al. / Inorganic Chemistry Communications 6 (2003) 469–473
471
Fig. 1.
A view of ionic moieties in the monomeric complex
½CuðPPh3Þ2ðoxineފðBF4Þ. The H atoms are not shown for clarity.
Fig. 2. A view of the ionic components of the monomeric complex
½CuðPPh3Þ2ðQuinފðBF4Þ. The H atoms are not shown for clarity.
Table 2
Table 3
ꢀ
ꢀ
Selected bond distances (A) and angles (°) for 1
Selected bond distances (A) and angles (°) of 2
Cu(1)–N(1)
Cu(1)–P(1)
2.037(2)
2.2549(7)
Cu(1)–P(2)
Cu(1)–O(1)
2.2675(8)
2.273(2)
Cu(1)–N(1)
Cu(1)–P(2)
2.069(2)
2.260(1)
Cu(1)–P(1)
2.268(1)
N(1)–Cu(1)–P(1)
N(1)–Cu(1)–P(2)
P(1)–Cu(1)–P(2)
120.83(6)
109.39(6)
122.76(2)
N(1)–Cu(1)–O(1)
P(1)–Cu(1)–O(1)
P(2)–Cu(1)–O(1)
76.14(8)
116.07(5)
100.34(5)
N(1)–Cu(1)–P(2)
N(1)–Cu(1)–P(1)
117.47(7)
110.15(7)
P(2)–Cu(1)–P(1)
128.50(3)
composed of two triphenylphosphine ligands and a N
atom from quinoline with normal bond distances for
ꢀ
Cu–N of 2.069(2) A and Cu–P of 2.260(1) and 2.268(1)
similar to that in ½Cuð2Me-quinÞðPPh3Þ2Š [O–Cu–
N ¼ 83.0(4)°] with the same CuP2NO core [11]. The
O–Cu–N angle in 1 is 76.14(8)°, but the P–Cu–P
[122.76(2)°], P–Cu–N [120.83(6)° and 109.39(6)°] and P–
Cu–O [100.34(5)° and 116.07(5)°] bond angles are closer
to the ideal tetrahedral geometry than the corresponding
values in ½Cuð2Me-quinÞðPPh3Þ2Š with P–Cu–P of
117.2(4)°, P–Cu–N of 128.8(2)° and 104.6(3)°, P–Cu–O
of 97.4(2)° and 117.2(4)°. This may be due to the ex-
treme steric crowding of the methyl group in the
Me-quin ligand in ½Cuð2Me-quinÞðPPh3Þ2Š. The bond
ꢀ
A. The dihedral angel between the P(1)–Cu(1)–P(2)
plane and the quinoline plane is 70.7°. The P–Cu–P
angle of 128.50(3)° is relatively larger than the other two
N–Cu–P angles of 117.47(7)° and 110.15(7)°, indicative
of steric hindrance effects from two bulky triphenyl-
phosphine ligands. For comparison, the P–Cu–P bond
angle in the ðPPh3Þ2CuO2CH2CO2H derivative is 131.1°
[15].
3.3. Photoluminescent properties
ꢀ
distances Cu–P [2.2549(7), 2.2675(8) A] and Cu–N
ꢀ
[2.037(2) A] in 1 are similar to those in ½Cuð2Me-quinÞ
The emission spectra of complex 1 and 2 in the solid
state at room temperature upon excitation at 330 nm are
illustrated in Figs. 3 and 4, respectively. Both spectra
show certain fine vibrational progression with maxima
at 519 and 512 nm, respectively. Many monomeric
Cu(I)–phosphine complexes display photoþluminescence.
One example is the ½CuðphenÞðPPh3Þ2Š system, in
which the emission originates from low-lying metal-to-
ligand charge transfer (MLCT) excited state with emis-
sion maximum at 605 nm [16]. As triphenylphosphine is
emissive at ꢀ470 nm [16], we assign that the emission for
both complexes are intraligand (oxine or quinoline) in
ꢀ
ðPPh3Þ2Š [Cu–P 2.202(3) and 2.308(4) A; Cu–N 2.071(9)
ꢀ
A] and other Cu(I)–triphenylphosphine or Cu(I)–(het-
erocyclic N-donor ligand) complexes [12,13]. The Cu–O
ꢀ
bond distance of 2.273(2) A in 1 is significantly longer
ꢀ
than those in ½Cuð2Me-quinÞðPPh3Þ2Š [2.088(14) A] and
in ½CuðPPh3Þ2ðH-NorfފðClO4Þ [2.074(2) and 2.0763(18)
ꢀ
A, H-Norf ¼ norfloxacine] [14], due perhaps to the at-
tachment of the proton in hydroxyl group of oxine.
The structure of complex 2 is shown in Fig. 2. Bond
distances and angles are reported in Table 3. The center
copper(I) ion assumes a trigonal coordination geometry

472
D. Li et al. / Inorganic Chemistry Communications 6 (2003) 469–473
CB2 1EZ, UK (Fax: +44-1223-336033; e-mail: de-
posit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk) or
from the corresponding author on request.
Acknowledgements
We acknowledge supports from the Nation Natural
Science Foundation of China (29901004) and Natural
Science Foundation of Guangdong Province of China
(000779).
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