Syntheses, crystal structures and properties of dinuclear copper(I) complexes

Article abstract of DOI:10.1016/j.molstruc.2011.09.005

Two dinuclear molecule-bridged Cu(I) complexes, (μ-bpym)[Cu(PPh ₃)Cl]₂ (1), [(μ-bpym)(CuL)₂](ClO ₄)₂·(CH₃CN)₂(H₂O) (2) (bpym = 2,2′-bipyrimidine, L = (R)-(+)-2,2′-bis(diphenylphospho) -1,1′-dinaphthalene) have been synthesized and characterized. The molecular structures of the two new dinuclear compounds exhibit bridging of two copper(I) centers by the symmetrically bis-chelating bpym ligand. Intriguingly, compound 1 features a remarkable "intramolecular organic sandwich" configuration where the central 2,2′-bipyrimidine bridging ligand interacts in π/π/π fashion with two phenyl rings from the coligands above and below the central plane, while chiral compound 2 exhibits second-order nonlinear optical effect and temperature-dependent luminescence. Upon decreasing the temperature from 298 to 10 K, compound 2 shows a red light emission.

Full text of DOI:10.1016/j.molstruc.2011.09.005

Journal of Molecular Structure 1007 (2012) 26–30
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Syntheses, crystal structures and properties of dinuclear copper(I) complexes
⇑
Chun-Hong Tan, Xiao Ma, Qi-Long Zhu, Yi-Hui Huang, Rui-Biao Fu, Sheng-Min Hu, Tian-Lu Sheng ,
Xin-Tao Wu
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 July 2011
Received in revised form 2 September 2011
Accepted 2 September 2011
Available online 10 September 2011
Two dinuclear molecule-bridged Cu(I) complexes,
(l-bpym)[Cu(PPh3)Cl]2 (1), [(l-bpym)(CuL)2]
(ClO4)2ꢀ(CH3CN)2(H2O) (2) (bpym = 2,20-bipyrimidine, L = (R)-(+)-2,20-bis(diphenylphospho)-1,10-dinaph-
thalene) have been synthesized and characterized. The molecular structures of the two new dinuclear
compounds exhibit bridging of two copper(I) centers by the symmetrically bis-chelating bpym ligand.
Intriguingly, compound 1 features a remarkable ‘‘intramolecular organic sandwich’’ configuration where
the central 2,20-bipyrimidine bridging ligand interacts in
p/p/p fashion with two phenyl rings from the
coligands above and below the central plane, while chiral compound 2 exhibits second-order nonlinear
optical effect and temperature-dependent luminescence. Upon decreasing the temperature from 298 to
10 K, compound 2 shows a red light emission.
Keywords:
Copper(I) compounds
Crystal structure
Intramolecular organic sandwich
Second-order nonlinear optical effect
Photoluminescence
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
2. Experimental
Copper(I) has been extensively used in the construction of elab-
orate and often fascinating supermolecular structures. Its rather
flexible coordination geometry and strong bonding to pyridine-
type nitrogen donor atoms have contributed to the formation of
catenates, molecular knots, helical and molecular grids [1–4]. Fur-
thermore, copper(I) complexes with polypyridyl ligands often exhi-
bit novel photophysical and electrochemical properties [5–7].
Taking into account the crucial role of polypyridyl ligands, biden-
tate coordination of ligand is desirable because of the chelate effect
2.1. Materials and methods
All the reactions were carried out under a nitrogen atmosphere
using Schlenk techniques. All reagents and solvents used were re-
ceived from commercial suppliers without further purification. The
structural determination of single crystal was performed on Rigaku
SCXmini diffractometer with graphite-monochromated MoK
a
(k = 0.71073 Å) radiation at room temperature. Elemental analyses
(C, H, and N) were performed with a Vario MICRO CHNOS Elemen-
tal Analyzer. The infrared spectra with KBr pellet were recorded in
the range of 4000–400 cmꢁ1 on a Perkin–Elmer Spectrum One FT-
IR Spectrometer. The solid-state luminescence emission/excitation
spectra were recorded on a FLS920 fluorescence spectrophotome-
ter. Powder X-ray diffraction (PXRD) data were collected on a
on complex stability and the enhancement of metal d
p–bridging li-
gand p –metal d electron interaction [8,9]. Polypyridyl ligand
p
p
2,20-bipyrimidine (hereafter abbreviated as bpym) is very useful
in synthesizing dinuclear copper(I) complexes as it can chelate
and bridge two metals. The bis(chelating) coordination mode of
the bpym allows the preparation of a series of bpym-bridged dinu-
clear complexes with the formula [M2(bpym)]+n where M = Zn [10],
Cu [11], Ni [12], Co [13], Fe [14] or Mn [15]. Recently, our attempts
DMAX-2500 diffractometer with CuKa.
2.2. Synthesis
concerning copper(I) afforded the new complexes of formula (
bpym)[Cu(PPh3)Cl]2 (1), [(
(2). Herein, we report the syntheses, structural characterisations
l-
l
-bpym)(CuL)2](ClO4)2ꢀ(CH3CN)2(H2O)
2.2.1. Synthesis of (l-bpym)[Cu(PPh3)Cl]2 (1)
To the solution of CuCl2 (0.068 g, 0.4 mmol) dissolved in meth-
anol (5 ml), triphenylphosphine (0.157 g, 0.6 mmol) in methane
dichloride (5 ml) was added. After 1 h, 2,20-bipyrimidine (0.032 g,
0.2 mmol) was added. The resulting solution was stirred at room
temperature for 4 h, and then the solvent was removed under vac-
uum. The residue was washed with acetonitrile and Et2O and
recrystallized in Et2O/CH2Cl2 to give compound 1 as prism red
and optical properties of these two compounds.
⇑
Corresponding author. Tel.: +86 591 83792837; fax: +86 591 83794946.
E-mail address: tsheng@fjirsm.ac.cn (T.-L. Sheng).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.09.005

C.-H. Tan et al. / Journal of Molecular Structure 1007 (2012) 26–30
27
Table 1
Table 3
Crystallographic data for compound 1.
Selected bond lengths (Å) and angles (°) of compound 1.
Empirical formula
Temperature (K)
Crystal color
Crystal size
Formula weight
Crystal system
Space group
a (Å)
C44H37N4P2Cl2Cu2
293(2)
Cu(1)–N(2)
Cu(1)–N(1)
2.109(2)
2.158(2)
78.22(7)
115.52(7)
104.06(6)
104.34(7)
106.53(6)
133.60(3)
113.23(15)
Cu(1)–P(1)
Cu(1)–Cl(1)
2.1896(12)
2.2476(11)
130.04(17)
116.2(2)
114.65(15)
129.17(19)
107.29(9)
116.76(9)
117.82(9)
Red
N(2)–Cu(1)–N(1)
N(2)–Cu(1)–P(1)
N(1)–Cu(1)–P(1)
N(2)–Cu(1)–Cl(1)
N(1)–Cu(1)–Cl(1)
P(1)–Cu(1)–Cl(1)
C(20)a–N(1)–Cu(1)
C(13)–P(1)–Cu(1)
C(1)–P(1)–Cu(1)
C(7)–P(1)–Cu(1)
C(21)–N(2)–Cu(1)
C(20)–N(2)–Cu(1)
C(20)–N(2)–C(21)
C(19)–N(1)–Cu(1)
0.20 ꢂ 0.10 ꢂ 0.10 mm3
881.7
Monoclinic
P21/n
14.515(8)
9.159(4)
b (Å)
c (Å)
16.616(9)
113.142(7)
2031.3(18)
2
Symmetry codes: (a) ꢁx + 1, ꢁy + 1, ꢁz.
b (°)
Volume (Å3)
Z
Density (calculated)
1.442
1.294
Abs. coeff. (mmꢁ1
)
Table 4
Selected bond lengths (Å) and angles (°) of compound 2.
F (000)
902
Refinement method
Reflections collections
Independent reflections
h range for data collection
h, k, l range
Full-matrix least-squares on F2
4659
Cu(1)–N(1)
2.161(6)
Cu(1)–P(1)
2.282(2)
2.307(2)
100.2(2)
116.4(2)
118.2(3)
110.0(2)
113.5(5)
129.7(5)
115.4(7)
114.2(5)
Cu(1)–N(2)
2.114(6)
Cu(1)–P(2)
3518 [(R(int) = 0.0350)]
2.59–27.50
N(2)–Cu(1)–N(1)
N(2)–Cu(1)–P(1)
N(1)–Cu(1)–P(1)
N(2)–Cu(1)–P(2)
N(1)–Cu(1)–P(2)
P(1)–Cu(1)–P(2)
C(7)–P(1)–Cu(1)
C(1)–P(1)–Cu(1)
C(49)–N(2)–Cu(1)
77.92(19)
127.37(17)
109.29(17)
122.54(17)
120.12(16)
99.26(7)
123.2(3)
118.5(2)
129.8(5)
C(13)–P(1)–Cu(1)
C(33)–P(2)–Cu(1)
C(39)–P(2)–Cu(1)
C(23)–P(2)–Cu(1)
C(47)–N(1)–Cu(1)
C(46)–N(1)–Cu(1)
C(48)–N(2)–C(49)
C(48)–N(2)–Cu(1)
ꢁ16 6 h 6 18, ꢁ11 6 k 6 11, ꢁ21 6 l 6 16
Goodness-of-fit on F2
Final R indices [I > 2sigma(I2)]
R (all data)
1.057
R = 0.0418, wR = 0.0968
R = 0.0605, wR = 0.1064
Table 2
Crystallographic data for compound 2.
Empirical formula
Temperature (K)
Crystal color
Crystal size
Formula weight
Crystal system
Space group
a (Å)
C100H76N6O9P4Cl2Cu2
293(2)
concentrated solution gave compound 2 as cubic red crystals in
61% yield (on the basis of 2,20-bipyrimidine). Anal. Calcd. For 2
Red
C100H78N6O9P4Cl2Cu2: C, 65.65; H, 4.30; N, 4.59. Found: C, 65.62;
0.30 ꢂ 0.20 ꢂ 0.20 mm3
H, 4.14; N, 3.16 (correspond to loss of two CH3CN, Anal. Calcd.
For C96H72N4O9P4Cl2Cu2: C, 65.98; H, 4.15; N, 3.21). IR (KBr,
cmꢁ1): 3053w, 1622w, 1565w, 1564m, 1500w, 1479w, 1436s,
1402s, 1306w, 1093vs, 1025w, 998w, 870w, 817m, 742s, 694s,
623m, 520m, 507m, 486w.
1827.53
Monoclinic
C2
18.068(13)
14.636(8)
b (Å)
c (Å)
18.676(13)
b (°)
116.596(9)
4416(5)
2
Volume (Å3)
Z
2.3. X-ray crystallography
Density (calculated)
1.37
0.678
1884
0.049(18)
Abs. coeff. (mmꢁ1
F (000)
)
The X-ray single crystal structure analyses for both the com-
pounds were performed on a Rigaku SCXmini diffractometer
Flack parameter
Refinement method
Reflections collections
Independent reflections
h range for data collection
h, k, l range
Full-matrix least-squares on F2
9928
(MoKa radiation, k = 0.71073 Å, graphite monochromator) at
293(2) K. Empirical absorption corrections were applied to the data
using the SADABS program [16]. The structures were solved by the
direct method and refined by the full-matrix least-squares on F2
using the SHELXL-97 program [17]. All of the non-hydrogen atoms
were refined anisotropically, and the hydrogen atoms attached to
carbon were located at their ideal positions. Crystal data are pre-
sented in Table 1 and 2. Selected bond lengths and angles are listed
in Table 3 and 4.
6188 [(R(int) = 0.0521)]
2.59 to 27.46
ꢁ23 6 h 6 15, ꢁ18 6 k 6 18, ꢁ24 6 l 6 24
Goodness-of-fit on F2
Final R indices [I > 2sigma(I2)]
R (all data)
0.989
R = 0.0685, wR = 0.1524
R = 0.1101, wR = 0.1777
crystals in 26% yield (on the basis of 2,20-bipyrimidine). Anal. Calcd.
For 1 C44H37N4P2Cl2Cu2: C, 59.94; H, 4.23; N, 6.35. Found: C, 60.02;
H, 4.10; N, 6.39. IR (KBr, cmꢁ1): 3046w, 1630m, 1558m, 1479w,
1434m, 1399s, 1262w, 1096m, 1022w, 821w,745m, 696s, 624w,
599w, 576w, 554w, 525m, 513m, 487m.
3. Result and discussion
3.1. Description of the structure
The structure of compound 1 consists of neutral bpym-bridged
[Cu2(bpym) (PPh3)2Cl2] dinuclear units (see Fig. 1). The metal ion is
in a tetrahedral environment which is composed of two nitrogen
atoms of a bpym ligand, one phosphorus atom of a triphenyl phos-
phine and one chlorine atom. The C20, N1, N2 and Cu1 atoms are
almost planar with the most deviation of 0.108(5) Å (Cu1). The
Cu–N bond distances are inequivalent with 2.158(2) Å for Cu(1)–
N(1) and 2.109(2) Å for Cu(1)–N(2) and the Cu–P bond distance
is 2.1896(12) Å. These Cu–N distances are in the normal range of
those observed in other similar Cu(I) complexes. While the Cu–P
2.2.2. Synthesis of [(
l
-bpym)(CuL)2](ClO4)2ꢀ(CH3CN)2(H2O) (2)
[Cu(CH3CN)4]ClO4 (0.049 g, 0.15 mmol) and R-(+)-BINAP (0.093
g, 0.15 mmol) were dissolved in methane dichloride (5 ml) and
stirred for 2 h at room temperature, then 2,20-bipyrimidine
(0.012 g, 0.075 mmol) was added. The reaction mixture immedi-
ately turned dark red and precipitated microcrystals. After five
hours, the solvent was removed under vacuum. The residue was
extracted with acetonitrile and methane dichloride (3:1) to give
a red solution, Subsequent diffusion of diethyl ether into the

28
C.-H. Tan et al. / Journal of Molecular Structure 1007 (2012) 26–30
close, e.g. at 3.24 Å for C8–N1 in 1, the distance between the cen-
troid of these planes is 3.72 (17) Å and 3.85 (17), confirming the
attraction. Besides, there exist weak hydrogen bonds involv-
p/p/p
ing the coordinated chlorine atoms and the H19A, H21A from
bpym (Fig. 3) [2.73(3), 2.71(3) Å for Cl(1)ꢀ ꢀ ꢀH(19A), Cl(1)ꢀ ꢀ ꢀH(21A),
respectively]. The molecular units are interdigitated into a two-
dimensional (2D) supramolecular framework directed by weak
hydrogen bonds.
The structure of complex 2 is composed of dinuclear [Cu2(b-
pym)L2] units, uncoordinated perchlorate anions, and crystalliza-
tion solvent molecules (water and acetonitrle). As shown in
Fig. 2, each copper atom is located in a distorted CuN2P2 tetrahe-
dral coordination environment with two nitrogen atoms from
bpym ligand and two phosphorus atoms of BINAP. The C47, N1,
N2 and Cu1 atoms are almost planar with the most deviation of
0.151(7) Å (Cu1). The Cu–N bond distances [2.161(6) Å for Cu(1)–
N(1) and 2.114(6) Å for Cu(1)–N(2)] are very close to that found
before[7,8,18,19]. And the Cu–P bond distances [2.282(2) Å for
Cu(1)–P(1) and 2.307(2) Å for Cu(1)–P(2)] are in agreement with
those in other reported four-coordinated Cu(I) species [7,8,18,
19,21].
It is noteworthy that unlike compound 1 and several analogs,
compound 2 holds no formation of an ‘‘organic sandwich’’ arrange-
ment between the central bpym bridge and two phosphino phenyl
rings (Fig. 4). This may be due to the effect of steric hindrance from
phosphine ligand BINAP. As a bulky rigid diphosphane, BINAP
would induce the steric crowding in the coordination shell and
hinder the ‘‘organic sandwich’’ arrangement [7,8,18,19]. At the
same time, the steric crowding makes some difference with bpym.
The bpym group is essentially planar in the dinuclear complex, but
it deviates somewhat from planarity in compound 2 (the dihedral
angle between the two pyrimidine rings is 10.886(15)°).
Fig. 1. Perspective view of compound 1. Hydrogen atoms have been omitted for
clarity. Symmetry codes: (A) ꢁx + 1, ꢁy + 1, ꢁz.
distance is slightly shorter than those reported value, which may
arise from the less steric constraint of chlorine atom [7,8,18,19].
The crystal structure of 1 exhibits a molecular arrangement
with a
central
p
p
/
p
/
p
sandwich formation involving the planar bpym as
acceptor and two phenyl rings from PPh3 coligands as do-
nors above and below (Fig. 1). Although not quite a classical stack-
ing [20] due to dihedral angle of about h = 18° between the Ph and
bpym planes and some atoms of the different rings coming rather
3.2. PXRD patterns and IR spectroscopy
As shown in Figs. 5 and 6, the experimental PXRD patterns of 1
and 2 are in good agreement with the simulated one except for the
relative intensity variations because of the preferred orientation of
the crystals, indicating that compounds 1 and 2 are both in a pure
phase.
Fig. 2. Perspective view of compound 2. Hydrogen atoms have been omitted for
clarity. Symmetry codes: (A) ꢁx + 1, y, ꢁz + 1.
Fig. 3. Crystal packing pattern of 1, viewed down the crystallographic a axis, showing the extended 2-D network formed through hydrogen bonding (dashed lines) linkages.
Hydrogen atoms have been omitted for clarity.

C.-H. Tan et al. / Journal of Molecular Structure 1007 (2012) 26–30
29
Fig. 4. Crystal packing diagrams of 2 viewed down the b-axis, Hydrogen atoms have been omitted for clarity.
It is well known that IR spectroscopy can be used as adiagnostic
tool for identifying the coordination modes of the 2,20-bipyrimi-
dine (bpym) ligand, which can act as a single chelate or as a bis-
chelate ligand [9,22,23]. Two intense absorption bands of nearly
equal intensities at about 1580 and 1560 cmꢁ1indicate the exis-
tence of terminal chelating mode of bpym, while an asymmetric
doublet or a single, strong broad band at near 1580 cmꢁ1 are asso-
ciated with the presence of bis-chelating mode oꢁf 1bpym [9,22,23].
Accordingly, the single broad band at 1558 cm for 1 and the
asymmetric doublet bands at 1564 and 1565 cmꢁ1 for 2 point to
the bis-chelate coordination mode for both compounds.
3.3. Photoluminescent and NLO properties
Considering the excellent photoluminescent properties of d10
complexes, the solid-state luminescences of compounds 1 and 2
were investigated at room temperature and freezing condition. It
is known that some fluorescent coordination polymers are sensi-
tive to the local coordination geometry of metal centers and mea-
surement temperature [24], which is also reflected on these
compounds. Compound 1 shows no luminescence in the solid state
at room temperature and at 10 K. Although the solid-state lumi-
nescence of compound 2 was hardly detected at room tempera-
ture, the emission spectrum at 10 K displays emission band
centered on 706 nm with excitation maximum at 360 nm, as
shown in Fig. 7. These observations indicate that thermal vibration
may play an important role on the photoluminescent property of
compound 2. When under freezing condition, thermal vibration
is inhibited basically and compound 2 give rise to red light emis-
sion. According to the previous reports about the polynuclear
Cu(I) clusters [25], this emission band may be attributed to the me-
tal-to-ligand charge transfer (MLCT).
Fig. 5. Experimental and simulated XRD patterns for compound 1.
Compound 2 crystallizes in the chiral monoclinic space group
C2 with flack parameter of 0.049(18) and exhibits second-order
nonlinear optical (NLO) effect as expected. A powdered sample of
2 is SHG active with a signal nearly the same as that of KH2PO4.
Fig. 6. Experimental and simulated XRD patterns for compound 2.

30
C.-H. Tan et al. / Journal of Molecular Structure 1007 (2012) 26–30
this article can be found, in the online version, at doi:10.1016/
j.molstruc.2011.09.005.
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Acknowledgements
This work was supported by grants from 973 program
(2007CB815301, the National Foundation of China (21073192,
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Appendix A. Supplementary material
CCDC Nos. 833215 and 833216 contain the supplementary crys-
tallographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, by emailing da-
ta_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crys-
tallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ,
UK. Fax: +44 1223336033. Supplementary data associated with
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