One‐pot concomitant preparation of two copper(II) coordination polymers with different configurations of bridging bithiophene ligands

By employing the conjugated bithiophene ligand 5,5′‐bis(1 H ‐imidazol‐1‐yl)‐2,2′‐bithiophene (bibp), which can exhibit trans and cis conformations, two different Cu II coordination polymers, namely, poly[[μ‐5,5′‐bis(1 H ‐imidazol‐1‐yl)‐2,2′‐bithiophene‐κ 2 N : N ′](μ 2 ‐4,4′‐oxydibenzoato‐κ 2 O : O ′)copper(II)], [Cu(C 14 H 8 O 5 )(C 14 H 10 N 4 S 2 )] n or [Cu(bibp)(oba)] n , (I), and catena ‐poly[μ‐aqua‐bis[μ‐5,5′‐bis(1 H ‐imidazol‐1‐yl)‐2,2′‐bithiophene‐κ 2 N : N ′]bis(μ 3 ‐4,4′‐oxydibenzoato)‐κ 3 O : O ′: O ′′;κ 4 O : O ′, O ′′: O ′‐dicopper(II)], [Cu 2 (C 14 H 8 O 5 ) 2 (C 14 H 10 N 4 S 2 )(H 2 O)] n or [Cu 2 (bibp)(oba) 2 (H 2 O)] n , (II), have been prepared through one‐pot concomitant crystallization and characterized by single‐crystal X‐ray diffraction, IR spectroscopy, elemental analysis, powder X‐ray diffraction (PXRD) and thermogravimetric (TG) analysis. Single‐crystal X‐ray diffraction indicates that the most interesting aspect of the structure is the existence of sole trans and cis conformations of the bibp ligand in a single net of (I) and (II), respectively. Compound (I) displays a threefold interpenetrating three‐dimensional framework with a 4‐connected {6 5 .8} cds topology, whereas (II) features a one‐dimensional chain structure. In the crystal of (II), the polymeric chains are further extended through C—H…O hydrogen bonds and C—H…π interactions into a three‐dimensional supramolecular architecture. In addition, strong intramolecular O—H…O hydrogen bonds formed between the bridging water molecules and the carboxylate O atoms improve the stability of the framework of (II). Furthermore, solid‐state UV–Vis spectroscopy experiments show that compounds (I) and (II) exhibit optical band gaps which are characteristic for optical semiconductors, with values of 2.70 and 2.26 eV, respectively.