Send Orders for Reprints to Reprints@benthamscience.ae Synthesis, Structural Characterization and Electrochemical Property of a Dinuclear Cu (ii) Complex Material

A novel dinuclear Cu(II) complex material has been synthesized by the reaction of 1, 2-phenylenedioxydiacetic acid, 1,10-phenantroline (phen) and Cu(CH 3 COO) 2 ·H 2 O. And it has been characterized by elemental analysis, IR, UV and single crystal X-ray diffraction. The crystal belongs to tetragonal, space group I4 1 /a with a = The structural analysis shows that two Cu(II) atoms adopt different coordination modes, Cu 1 has five-coordination with a trigonal bipyramidal configuration, and Cu 2 has four-coordination with a distorted square planar configuration. The cyclic voltammetric behaviour of the dinuclear Cu(II) complex has been investigated.


INTRODUCTION
The design and synthesis of Cu (II) complex have always attracted considerable interest, as the Cu (II) complexes have potential applications in so many respects.For example, they can build intriguing molecular architectures [1,2], and can exhibit excellent properties in molecular magnetism, catalysis, antitumor therapeutic agents, and electrochemistry [3][4][5][6][7][8][9][10]. Both carboxylates and phen are good organic ligand because they not only have rich coordination points and strong coordination ability but can also construct the molecular structure of multiple structures [11][12][13].We have synthesized a novel dinuclear Cu(II) complex by the selfassembly of 1, 2-phenylenedioxydiacetic acid, 1,10phenantroline (phen) and Cu(CH 3 COO) 2 •H 2 O in the presence of MgCl 2 [14].For comparison, we synthesized and reported herein another novel dinuclear Cu(II) complex, based on 1, 2-phenylenedioxydiacetic acid and phen ligands without the presence of MgCl 2 .The cyclic voltammetric behaviour of the Cu(II) complex has also been investigated.C, H and N analyses were carried out with a Elementar Vario III EL elemental analyzer.Infrared spectra (4,000 cm -1 ~400 cm -1 ) were recorded on a Nicolet AVATAR 360 FTIR spectrophotometer with KBr discs.Ultraviolet-Visible *Address correspondence to this author at the College of Chemistry and Chemical Engineering, Weifang University, Weifang 261061, China; Tel: +86-536-8785363; Fax: +86-536-8785363; E-mails: taixishi@lzu.edu.cn,taixs@wfu.edu.cnspectra in the 200-700 nm region in H 2 O solution were recorded on a thermo UV-340 spectrophotometer.CHI660D electrochemical work station was used.The crystal data of dinuclear Cu (II) complex was collected on a Bruker smart-1000 CCD Area Detector.

X-Ray Crystallography
All crystal data were collected on a Bruker Smart-1000 CCD diffractometer equipped with a graphite-monochromatic Mo Kα radiation (λ = 0.71073 Å) at 293(2) K.In the range 3.01-27.48°,a total of 88570 reflections were collected by using an ω scan mode, of 6465 with I > 2σ(I) were independent with R int = 0.0621.The structure was solved by direct method and refined with full-matrix leastsquares techniques using SHELXL-97 [15].All nonhydrogen atoms were refined anisotropically, and all hydrogen atoms were added according to the theoretical model.Molecular graphics were drawn with the program package SHELXTL-97 crystallographic software package [16].The crystal parameters data collection and refinement results for dinuclear Cu(II) complex are summarized in Table 1.The selected bond distances and angles are listed in Table 2.

IR Spectra
The free 1,2-phenylenedioxydiacetic acid and phen ligands show bands at 1670 cm −1 ν(COO -) and 1582 cm −1 ν(C=N) of phen, respectively.In the IR spectrum of Cu (II) complex (Fig. 1), they appear at 1564 cm −1 and 1513 cm −1 , respectively, which indicates that the oxygen atoms of COO - and the nitrogen atoms of phen are coordinated to Cu (II) ion [17].The results of IR analysis are consistent with the results of X-ray analysis.

UV Spectra
As shown in Fig. (2), the free 1, 2-phenylenedioxydiacetic acid ligand exhibits two absorption bands at 224 nm and 271 nm, which can be assigned to the π-π transitions of the organic ligand.However, the Cu (II) complex show three peaks at 221 nm, 273 nm and 600 nm.The two absorption bands at 221 nm and 273 nm can be assigned to the π-π transitions and the absorption at 600 nm can be assigned to d-d transition.Which indicates that the stable complex is formed by the interaction of ligand and the Cu (II) ion.

Structure Description
The molecular structure and molecular packing arrangement are shown in Figs.(3,4), respectively.Fig. (5) shows the topological structure of the Cu (II) complex.The structure of Cu (II) is different from that of the Cu(II) complex reported previously [14], indicating that the same ligand and metal ion can form different structure when the synthetic condition was changed.As shown in Figs.(3,4), the Cu 1 ion is five-coordinated by two oxygen atoms from 1, 2-phenylenedioxydiacetic acid ligand, one oxygen atom from coordinated water molecule and two nitrogen atoms from phen ligand to form a distorted square pyramid coordination environment.And the Cu 2 ion is fourcoordinated by two oxygen atoms from 1,2phenylenedioxydiacetic acid ligand and two nitrogen atoms from phen ligand to form a distorted square planar coordination environment.The bond distances of Cu-O are in the range of 1.898(5) Å -2.347 (5) and that of Cu-N bonds are in the range of 1.995(6)-2.036(5)Å, respectively.The Cu-O distances and Cu-N distances are close to those of the Cu (II) complex reported previously [18][19][20].

Cyclic Voltammetry of Cu (II) Complex
The electrochemical behavior of the Cu (II) complex was determined, and the process of measurement is the same with those reported previously [14].As shown in Fig. ( 6), there appears an obvious oxidation peak at 391 mV, however, no reduction peak is observed, showing that the Cu(II) complex only has reducibility and no oxidizability.

CONCLUSION
A novel dinuclear Cu (II) complex, based on 1, 2phenylenedioxydiacetic acid and 1,10-phenantroline (phen) ligands without the presence of MgCl 2 has been synthesized with structural characterization.In this structure, the Cu (II) atoms adopt two different coordination modes.The cyclic voltammetric behavior of the dinuclear Cu (II) complex has been investigated.

SUPPLEMENTARY MATERIAL
Crystallographic data for the structure reported in this paper has been deposited with the Cambridge Crystallographic Data Centre as supplementary publication No. CCDC 1030752.Copy of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk).
Educational Science and Technology Program (J14LC01) and the Natural Science Foundation of Shandong (ZR2014BL003).