Synthesis, characterization and crystal structures of three diverse copper (II) complexes with thiophene-2,5-dicarboxylic acid and 1,10-phenanthroline

Abstract

Three copper (II) complexes with thiophene-2,5-dicarboxylic acid (H2Tda) and 1,10-phenanthroline (phen) ligands have been synthesized and structurally characterized: [Cu (Tda) (phen) (H2O) 2] ·3H2O (1) , [Cu (Tda) (phen) 2] ·12H2Tda·2H2O (2) and [ {Cu (Tda) (phen) (H2O) } n] (3) . The Cu atom in all of the three complexes is in five coordinate, distorted square pyramidal environments. The thiophene-2,5-dicarboxylate molecule is monodentate in 1 and 2 in which the molecular structure is stabilized by intermolecular aromatic ring stacking interaction between the thiophene ring and the aromatic rings in the 1,10-phenanthroline molecule and hydrogen bondings. In 3 the thiophene-2,5-dicarboxylate ion is bis-monodentate and bridges the [Cu (phen) (H2O) ] units to form a one-dimensional polymer. Complex 2 shows quasi-reversible one-electron redox of Cu2Cu+ at 0.001 V vs SCE. Coordination environments of copper (II) in the reported complexes and stacking interactions in 1 and 2 are compared with those in the copper (II) site of galactose oxidase (GOase).