XUE Li-Ping CUI Ji-Ji ZHANG Ting GAOYue YAO Ji-Xin

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Construction of a New Two-fold Interpenetrated Three-dimensional Cobalt(II) Coordination Polymer Based on 2,5-Thiophenedicarboxylic Acid and Bis(imidazol-1-yl)methane①

XUE Li-Pinga②CUI Jia-JiabZHANG TingbGAOYuebYAO Jia-Xinba

(471934)b(471934)

A cobalt coordination polymer, {[Co2(tdc)2(bimm)2]·(3DMF)}n, was synthesized based on 2,5-thiophenedicarboxylic acid (H2tdc) and bis(imidazol-1-yl)methane (bimm) mixed ligands. The asymmetric unit of the complex contains two Co2+cations, two tdc2?dianions, two neutral bimm ligands, and three free DMF molecules.In the complex, deprotonatedtdc2-dianions alternately bridge the adjacent Co2+cations to generate chains, which are further connected by the flexible bimm ligands to form a 3Dstructure containing adamantanoid-like subunits. In topology, the structure of 1 represents a 4-connecteduninodaltwo-fold interpenetrateddia (66) topology. Moreover, the solid UV-Vis absorption spectra of the complex have also been investigated.

cobalt coordination polymer,2,5-thiophenedicarboxylic acid,bis(imidazol-1-yl)methane, crystal structure, dia topology;

1 INTRODUCTION

Coordination polymers (CPs) are attractive func- tional materials with considerable promises in gas storage, luminescence, molecular magnetism, he-terogeneous catalysis, drug delivery and molecular separation[1-4]. Generally speaking, the design and construction of target CPs materials are still a great challenge, as many factors like organic ligands, solvent, pH, counter anion, concentration and tem- perature are associated with its synthesis[5-7]. Among the above-mentioned factors, the selection of appropriate organic ligands is very important, and a great deal of significant work has been done by using the strategy.

The rigid 2,5-thiophenedicarboxylic acid (H2tdc) with C2-like symmetry is a good exo-bidentate linker and becomes conspicuous and indispensible in CPs owing to its structural rigidity and chemical robustness. For example, Furukawa et al. reported a 2-fold interpenetrating zinc CP with 6-connected lcy net[8]. Zhang et al. reported three anionic CPs with bcg, bcu and flu topologies by tuning different organic cations[9]. In addition, the combination of H2tdc with N-donor co-ligands is also an effective paradigm for the synthesis of CPs[10-12]. Compared with flexible bridging pyridyl ligands, the combination of H2tdc and bis(imidazole) co-ligands in the self-assembly of CPs is rarely documented to date. Thus, these considerations inspired us to construct new CPs with H2tdc and flexible bis(imidazole) co-ligands.

In our previous study, we have employed H2tdc and flexible bis(imidazol-1-yl)methane (bimm) mixed ligands to construct threehighly-connected cadmium CPs, which show 4-connected sql layer, 6-connected 2-fold interpenetratedpcu and 8-con- nected bcu-type network, respectively[13].Herein, we report a new three-dimensional (3D) CP, {[Co2(tdc)2(bimm)2]·(3DMF)}n, based on H2tdc and bimm mixed ligands, featuring a 2-fold interpene- trating net with dia topology. What’s more, the solid UV-Vis absorption spectra of the complex were investigated.

2 EXPERIMENTAL

All chemicals for the syntheses were purchased from commercial sources and used without further purification. The hydrothermal reaction was per- formed in a 30 mL Teflon-lined autoclave under autogenous pressure. Elemental analyses for C, H, and N were carried out on a Flash 2000 elemental analyzer. Thermogravimetric analyses (TGA) were carried out on a SDTQ600 thermogravimetric analyzer. A platinum pan was used for heating the sample with a heating rate of 10 ℃/min under a N2atmosphere. Powder X-ray diffraction (PXRD) measurements were performed on a Bruker D8- ADVANCE X-ray diffractometer with Curadiation (= 1.5418 ?). The UV-Vis absorption spectra were recorded with a Hitachi U-4100 spectrophotometer.

2. 1 Synthesis of {[Co2(tdc)2(bimm)2]·(3DMF)}n

A mixture of H2tdc (0.034 g, 0.2 mmol), Co(NO3)2·6H2O (0.046 g, 0.2 mmol), bimm (0.029 g, 0.2 mmol), and 8 mL deionized water was sealed in a 25 mL Teflon-lined stainless-steel vessel and heated at 120 °C for 3 days under autogenous pre- ssure, followed by cooling to room temperature at a rate of 5 °C·h-1. Pink block crystals of 1 were collected (yield: 52% based on Co). Elemental analysis calcd. (%) for C35H41Co2N11O11S2: C, 43.13; H, 4.21; N, 15.82. Found (%): C, 43.11; H, 4.23; N, 15.79.

2. 2 X-ray structure determination

3 RESULTS AND DISCUSSION

Table 1. Selected Bond Lengths (?) and Bond Angles (°)

Symmetry transformation: #1:– 1,+ 1,; #2:+ 1,,– 1; #3:1,– 1,– 1

Fig. 1. Coordination environment of the Co2+cations in 1, showing the atom numbering scheme.Displacement ellipsoids are drawn at the 30% probability level. All hydrogen atoms are omitted.Symmetry codes: (#1)– 1,+1,; (#2)+1,,–1; (#3)+1,–1,–1

Fig. 2. (a) 1D polymeric chain. (b) View of the 3D framework of 1

Fig. 3. (a) View of a single diamond motif in 1. (b) Schematic view of a single 3D diamond framework. (c) Schematic representation of the 2-fold interpenetrating 3D diamond framework

To confirm the phase purity of complex 1, the PXRD pattern was recorded. As seen in Fig. 4a, the peak positions of the experimental and simulated patterns matched well, and there are no other peaks in the bulk material powder diffraction pattern, indicating the pure phase of the obtained product. Thermogravimetric analysis (TGA) was also investigated for complex 1 under N2atmosphere at a heating rate of 10 °C·min?1(Fig. 4b). The weight loss of 22.67% from 80 to 300 °C is attributed to the loss of free DMF molecules (calcd. 22.52%). The abrupt weight loss corresponding to the release of organic ligands starts at 300 °C with a result of thermal decomposition with the residual weight at ca. 17.10%.

In order to further characterize complex 1, the UV-vis absorption spectra of complex 1 together with the solid H2tdc and bimm ligands at room temperature are investigated(Fig. 5). The H2tdc ligand mainly exhibits one peak at 298 nm and the bimm ligand itself displays absorption bands at 216 nm with a weak shoulder band at 288 nm. The absorptions of the free organic ligands may be ascribed to the-* transition. In contrast, the coordination to the Co2+ion in complex 1 obstructs the-* electron transition and the resulted complex 1 displays one absorption at 264 nm, while a wide band in the range of 416～650 nm results from thespin-forbidden transition of the Co2+ion[18].

Fig. 4. (a) XRD patterns of 1 simulated from X-ray single-crystal diffraction data and experimental data. (b)TGA curve for 1

Fig. 5. UV-vis absorption spectra for free organic ligands and 1

4 CONCLUSION

In summary, a cobalt coordination polymer was synthesized based on 2,5-thiophenedicarboxylic acid and bis(imidazol-1-yl)methanemixed organic ligands. The compoud is a two-fold interpenetrated 3D colt(II) coordination polymer with 4-connected dia(66) topology. Moreover, the solid UV-Vis absorption spectra of the complex have also been investigated.

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2 December 2017;

20 March 2018 (CCDC 1476869)

①This work was supported by the Natural Science Foundation of Henan Province (172102310333)

. Doctor, majoring in material chemistry. E-mail: lpxue@163.com

10.14102/j.cnki.0254-5861.2011-1922