КООРДИНАЦИОННАЯ ХИМИЯ, 2010, том 36, № 1, с. 49-53
УДК 541.49
SYNTHESIS, CRYSTAL STRUCTURE, AND THIRD-ORDER NONLINEAR OPTICAL PROPERTIES OF A COPPER(I) ONE-DIMENSIONAL
COORDINATION POLYMER
© 2010 Y. Li1*, Z. X. Zhang1, T. Li2, and K. C. Li3
1College of Science, Guangdong Ocean University, Zhanjiang 524088, P.R. China
2College of Chemical Engineering and Light Industry, Guangdong University of Technology,
Guangzhou 510006, P.R. China
3College of Chemistry, Jilin University, Changchun 130023, P.R. China
*E-mail: yongli6808@126.com
Received April 1, 2009
A copper(I) thiocyanate coordination polymer [Cu(Phen)(p.-NCS)]n (I) (Phen = 1,10-phenanthroline) has been synthesized by the low-temperature solid-state reaction. Single- crystal X-ray analyses reveal that compound I possesses a type of one-dimensional (1D) framework structure. Polymer I was characterized by elemental analyses, IR spectra, and UV-visible spectra. The third-order nonlinear optical properties were also investigated, and they exhibit good nonlinear absorption and self-defocusing performance with modulus of the hyperpolarizability 4.94 x 10 esu for I in a 6.35 x 10-4 mol dm-3 DMF solution.
INTRODUCTION
Recently, the design and assembly of coordination polymers have been ofgreat interest due to their interesting topologies [1—4] and potential applications as catalysts, superconductors, magnetic, and optical materials [5—9]. A rational selection of ligand presented, metal center, type of the anion, and reaction conditions can confer control over the topology of the resulting networks. Employment of two same metals (such as Cu) or different metals (such as Cu and Cd) [10] in the preparation of coordination polymers may be expected to increase the diversity and complexity of the coordination polymers. Moreover, the simultaneous presence of thiocyanate ion and Phen ligand, which are attractive linkers from the point ofview of crystal engineering, may lead to novel polymeric network topologies. The Phen ligand has been known to be a versatile ligand, which may coordinate to metal atoms in many different ways and thus the crystal engineering of coordination polymers containing Phen ligand has attracted great attention [11]. The pseudohalide NCS- is known to coordinate to metals in both terminal and bridging modes. As bridging ligand the thiocyanate can link a pair of metal centers in either an end-on (|-1,1-NCS, |-1,1-SCN) or end-to-end (|-1,3-NCS) configuration. The thiocyanate ion may link a third metal atom giving rise to a |-1,1,3-NCS (|-N,N,S) or |-1,1,3-SCN (|-S,S,N) mode:
M
,N-C—S' m'
ц = 1,3-NCS
M M
'N-C—S M'
ц = 1,1,3-NCS
M
M
N-C—S
.S—C—N
M M
ц = 1,1-NCS ц = 1,1-SCN
M
M
^S—C—N M
ц = 1,1,3-SCN
Binuclear and polynuclear copper thiocyanate systems are ofconsiderable interest owing to the broad range of their structural and magnetic properties [12]. However, the vast majority of studies have focused on copper(II) thiocyanate complexes [13]. On the other hand, reports on copper(I) thiocyanate complexes are relatively few. For example, [Cu2L(|-SCN)2] (L = macrocyclic Schiff base) [14] and [Cu2(|-Ph2Ppypz)2(|-SCN)][ClO4] (Ph2Ppypz = 2-(diphenylphosphino)-6-(pyrazol-1-yl) pyridine] [15], which exhibit |-1,1-SCN bridges have been established.
As a part of our work toward rational design and preparation of functional compounds, we carried out a study on copper(I) coordination polymer with thiocyanate and Phen ligands. This compound is synthesized by low-temperature solid-state reaction and is not traditionally synthesized in solution [16]. This low-temperature solidstate synthesis method has great significance in reducing environmental pollution. As for nonlinear optical (NLO)
4 КООРДИНАЦИОННАЯ ХИМИЯ том 36 № 1 2010
Table 1. Crystal and structure data refinement for [CuPhen(p.-NCS)]B. Estimated standard deviations are given in parentheses
Parameter Value
Formula weight 301.82
Crystal system Monoclinic
Space group P2x/c
Unit cell dimension:
a, A 9.0187(5)
b, A 12.7580(7)
c, A 1.3738(6)
ß, deg 107.7520(10)
V, A3 1246.36(12)
Z 4
Pcalcd g/cm3 1.608
/(000) 608
Absorption coefficient, mm-1 0.944
Crystal size, mm3 0.21 x 0.16 x 0.14
9 range, deg 3.00-28.23
Limiting indices -11 < h < 11
-16 < k < 14
-14 < l < 15
T, K 273(2)
Reflections collected/unique 4558/1847 (Rint = 0.0261)
Refined parameters 158
GOOF 0.914
Final R indicates (I > 2a(T)) Rx = 0.0261, wR2 = 0.0597
Largest diff. peak and hole, e A-3 0.171 and -0.171
performance, the studies in the last decade have been largely focused on semiconductors, conjugated polymers, and discrete organic molecules [17, 18], as well as fullerene C60 [19], while coordination polymers (a very promising class of compounds as NLO materials) have not received enough attention. We are interested in developing both novel structures and NLO materials of coordination polymers. We report here the solid-state synthesis, structural characterization, and the third-order NLO properties of Cu(I) coordination polymer [Cu(Phen)(|-NCS)]n (I); Phen = 1,10-phenanthroline.
EXPERIMENTAL
The solvents were carefully dried and distilled prior to use, and other chemicals from commercial sources were used without further purification.
Physical measurements. Infrared spectra (KBr pellet) were recorded on a Perkin Elmer Spectrum One FT-IR spectrometer in the 225—4000 cm-1 region. The Cu element was determined by a Perkin Elmer Optima 3300DV spectrometer. Elemental analyses (C, H, S, and N) were performed on a Perkin Elmer 2400 Series
IICHNS/O elemental analyzer. Electronic spectra were measured on a Shimadzu UV-3100 spectrophotometer. The NLO measurements were performed with Z-scan technique in the DMF solution; the DMF solution was contained in 5-mm-thick glass cell with a concentration of 6.35 x 10-4 mol/l. The NLO response of the solution was measured at 532 nm with a 15-ns pulse width produced by a frequency-doubled Q-switched Nd: YAG laser [20].
Synthesis of I. A well-ground mixture of CuBr (144 mg, 1.0 mmol), NaSCN (163 mg, 2.0 mmol), and Phen (595 mg, 3 mmol) was heated in a sealed glass tube filled with N2 gas at 85°C for 24 h. The mixture was extracted with the mixed solvent of CH3CN (15 ml) and CH3OH (40 ml) and then filtered. The thin blue filtrate remained in the atmosphere of nitrogen at 5°C for 10 days, and the thin blue crystals were obtained, an a yield of 37.8% based on Cu. IR spectrum (v, cm-1): 2878 w v(C-H); 2111 v.s v(C-N); 780 m v(C-S); 629 m v(Cu-NPhen); 452 m v(Cu-NNCS); 415 m v(Cu-SSCN). The results of elemental analyses:
For C13H8CuN3S
anal. calcd, %:C 51.73; H 2.67; N 13.92; S 10.62; Cu 21.05. Found, %: C 51.75; H 2.68; N 13.90; S 10.64; Cu 21.09.
X-ray structure determination. Crystal data were collected with Mo^ radiation (k = 0.71073 A) using a Siemens SMART CCD diffractometer for I. The structure was solved using a direct method with the SHEXTL-97 program and refined by full-matrix least-squares technique. The non-hydrogen atoms were assigned by aniso-tropic displacement parameters in the refinement; the hydrogen atoms were treated using a riding model. The crystal data are given in Table 1, and selected bond lengths and angels are in Table 2.
The atomic coordinates and other parameters of structure I have been deposited with the Cambridge Crystallographic Data Center (no. 699879; depos-it@ccdc.cam.ac.uk).
RESULTS AND DISCUSSION
The synthesis of the title polymer could be presumed as follows:
nCu+ + «Phen + n NCS- — [CuPhen(|-NCS)]n . (I)
As shown in Fig. 1, the Cu+ cation is four-coordinated by two nitrogen atoms from the Phen ligand and two atoms of nitrogen and sulfur from the two SCN ligands. The distorted tetrahedral environment [CuN3S], with the fundus plane defined by the N(1), N(2), and n(3) atoms and one apical position occupied by the S atom. The Cu-N(1) and Cu-N(2) distances are 2.097(2) and 2.097(2) A, respectively, which are compared with other analogous Phen derivatives of Cu(I) coordination compound [21]. The Cu-S and Cu-N(3) distances are 2.3120(7) and 1.906(2) A, respectively, which are similar to that in complex [Cu(Dach)(|-NCS)(NCS)]n (Dach
KOOP,3HHAUHOHHAH XHMH3 tom 36 № 1 2010
SYNTHESIS, CRYSTAL STRUCTURE, AND THIRD-ORDER NONLINEAR
51
= 1.4-diazacycloheptane) [22]. The deformation of the distorted tetrahedron given by the acute angle of N(1)CuN(2) is 80.02(8)°, and the obtuse angles of NCuN or NCuS vary from 107.87(6)° to 120.53(9)°. The thiocyanate group is almost linear with an NCS angle of 177.9(3)°, which shows the normal structure moiety; C(13)-N(3) 1.156(3), C(13)-S(4) 1.653(2) Â. Among the rest, the ^-1.3-NCS ligands join the adjacent Cu+ ion along z axis to one-dimensional (1D) zigzag chain structure, which is formed through the —Cu—CNS—Cu—CNS— linear chain (Fig. 1). The distance between the adjacent copper atoms in the same chain is 5.693(1) Â, which is shorter than Cu—Cu 6.113 Â in analogous CNS derivatives of Cu coordination compound [23].
The UV-visible absorption spectrum of the title compound (6.35 x 10-4 mol dm-3 in DMF) displays one strong absorption peak (with molar absorption coefficients in dm3 mol-1 cm-1) at 274 (4.84 x 103) nm and one medium-absorption peak 289 (2.00 x 103) nm. The peak at 274 nm is attributed to center ion — ligand chargetransfer transitions, and the peak at 289 nm is a broad absorption with a long tail up to 700 nm assigned to a d—d transition. The polymer has relatively low linear absorption in the ultraviolet and visible region, and the wide peak extending into visible region shows the presence of charge-transfer transitions. Promising low-intensity loss and little temperature change caused by photon absorption when pulsed light propagates in the materials show that the polymer has potential as an optical limiter [24].
The third-order NLO properties of the title compound were investigated by using a Z-scan technique. The cell being selected to place the sample is 5 mm thick glass
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