Synthesis and Crystal Structure of a Cu(II)Coordination Polymer: [Cu(L)(1,10-phen)]n①

WANG Cui-Cui YANG Ge-Ge LI Hi-Ye② JIANG Yi-Min,

a (School of Chemistry and Pharmaceutical Sciences of Guangxi Normal University, Guilin 541004, China)

b (Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources of Guangxi Normal University, Guilin 541004, China)

1 INTRODUCTION

Metal-organic coordination polymers have been given more research attention recently not only for their intriguing variety of architectures and topologies[1], but also for their applications of physiology and pathology[2,3]. Many N-containing ligands, such as 4,4?-bipyridine, 2,2?-bipyridine and 1,10-phenanthroline, have been widely applied in constructing coordination polymers as auxiliary ligands[4,5]. π-π stacking interactions are frequently existent, and are inclined to form extended multi-dimensional structures from low-dimensional ones[1,6-22]. In this paper,we report the synthesis of 1. It has been studied and characterized by IR, elemental analysis, and singlecrystal X-ray diffraction together with thermogravimetric analysis.

2 EXPERIMENTAL

2.1 Materials and measurements

All solvents and chemicals were commercial reagents and used without further purification. IR spectra were taken on a Perkin-Elmer spectrum One FT-IR spectrometer in the 4000～400 cm-1region with KBr pellets. Elemental analyses for C, H and N were carried out on a Model 2400 II, Perkin-Elmer elemental analyzer. The crystal structure was determined by a Bruker P4 CCD.

2.2 Synthesis of the title complex

Cu(OAc)2·H2O (0.0610 g, 0.25 mmol) and H2L(0.0372 g, 0.17 mmol) were dissolved in 10 mL ethanol and 10 mL water. The mixture was stirred at 323 K for 10 min followed by adjusting the pH value to 6.0 with 1 mol/L KOH solution. The reaction continued for 3 h, 5 mL ethanol solution of 1,10-phen (0.0840 g, 0.17 mmol) was added, then stirred at 323 K for 4 h, and finally filtered. The blue solution was set aside for 30 days for the growth of blue block-shaped crystals. Such crystals of the title complex were separated from the reaction mixture,yield: 20% (0.0500 g). Anal. Calcd. (%) for C19H14CuN4O4S: C, 47.83; H, 3.10; N, 12.16. Found(%): C, 49.79; H, 3.06; N, 12.23. (KBr, cm-1):3747m, 3460m, 2342w, 1623s, 1585s, 1519w, 1421w,1382s, 1276s, 1143s, 1111s, 890m, 722m, 600m.

2.3 X-ray crystallography

A suitable crystal of the title complex (blue, dimensions of 0.51mm × 0.23mm × 0.10mm) was used for structure determination. Data collection at 293(2) K was carried out with a Bruker P4 CCD instrument using a MoKα radiation (λ = 0.71073 ?)at 293(2) K with an ω-scan mode. The structure was solved by direct methods with SHELXS-97 and refined by full-matrix least-squares on F2using SHELXL-97[23,24]. All non-hydrogen atoms were assigned anisotropically. The hydrogen atoms were generated theoretically and treated by a mixture of independent and constrained refinement. For the complex, convergence was reached at the final R =0.0368 (I ＞ 2σ(I)) and wR = 0.0943 (for all data),with allowance for the thermal anisotropy for all non-hydrogen atoms.

3 RESULTS AND DISCUSSION

3.1 Crystal structure of the title complex

Selected bond lengths and bond angles are listed in Table 1. The molecular structure of the title complex is illustrated in Fig. 1.

Table 1. Selected Bond Lengths (?) and Bond Angles (o) for the Title Complex

Fig. 1. Molecular structure of the title complex (All H atoms are omitted for clarity)

The molecular structure of the title complex[Cu(L)(1,10-phen)]nestablished by X-ray analysis reveals that the title complex is a 1D chain polymer(Fig. 2). Each Cu(II) ion is coordinated by five atoms in a square pyramidal geometry, bonded to two nitrogen atoms (Cu(1)–N(2) = 2.022(2) ?,Cu(1)–N(3) = 2.004(2) ?) from 1,10-phen, one carboxyl oxygen (Cu(1)–O(1) = 1.9504(19) ?) and one amino nitrogen (Cu(1)–N(1) = 1.975(3) ?) from H2L, and one carboxyl oxygen (Cu(1)–O(2) =2.238(2) ?) from another ligand L. The N(1), N(2),N(3) and O(1) atoms are coplanar while O(2) occupies the axial position. So, each Cu(II) ion is coordinated in an elongated square pyramidal geometry.

Fig. 2. 1D chain structure of the title complex via the c axis

Each central Cu(II) ion is bridged by L2-ligand to form an infinite chain structure. Two adjacent chains are parallel and there exist π-π stacking interactions between the Phen rings of neighboring chains along the c axis (Fig. 2). The average distance and ring-centroid separation are 3.330(1) and 3.886 ?,respectively. These 1D chains are further expanded into a 3D supramolecular structure through π···π interactions of Phen and Phen, and Phen and pyridine of L2-ligand (Fig. 3). It is similar with the review[1].

Fig. 3. Packing diagram of the title complex via the a axis

3.2 IR spectrum of the title complex

IR spectrum of compound 1 exhibits broad absorption centered at 3747 and 3460 cm-1for the existence of N–H and O–H. The absorption at 1382,1276, 1143, 1111 and 1276 cm-1in the 1000～1380 cm-1region is typical for the sulfonyl groups of L,and the absorption at 1623 cm-1is ν(C=O) from L. It exhibits characteristic absorption at 1585, 890 and 722 cm-1due to ν(C=N) and δ(C–H) attributed to the coordinated phen ligand.

3.3 Thermogravimetric analysis

Thermogravimetric analysis (TGA) was performed on power samples of the title compound in a nitrogen atmosphere from 15 to 1000 ℃ at a rate of 10 ℃/min by Pyris Daimond TG-DTG, as shown in Fig. 4. The first weight loss of 63.72% (ca. 63.61%)between 188 and 358 ℃ corresponds to the release of 1,10-phen ligand, pyridine ring and sulfur of compound 1. Basic skeleton of the complex has been partially exploded. A weight loss of 10.11% (ca.10.04%) at 358～971 ℃ is assigned to the removal of nitrogen and two oxygen atoms of glycine. The decomposition process ends at about 971 ℃ and the final residue is probably CuO and sulfur atom(remaining weight found: 26.17%, ca. 24.46%).

Fig. 4. TG curve of the title complex

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