Structural elucidation of novel mixed ligand complexes of 2-thiophene carboxylic acid [M(TCA)2(H2O)x(im)2] [x = 2 M: Mn(II), Co(II) or Cd(II), x = 0 Cu(II)]

Abstract

Novel mixed ligand complexes containing thiophene-2-carboxylic acid (HTCA) and imidazole (im) ligands, [M(TCA)2(H2O)2(im)2] (M: Mn, Co, Cd) and [Cu(TCA)2(im)2] were obtained. The complexes were characterized by X-ray single crystal diffraction. Also, spectroscopic (IR and UV-Vis), magnetic and thermal properties were investigated. The thiophene-2-carboxylate acted in a monoanionic monodentate manner and bonded to the metals via its carboxylate oxygen. The im ligands bonded to the metals via hydrogen free nitrogen atoms. The geometry around the metal centers was octahedral [MO4N2] for Mn(II), Co(II) and Cd(II) complexes and square-planar [CuO2N2] for the Cu(II) complex. Due to intermolecular interactions in the solid state, the Co(II), Mn(II) and Cd(II) complexes showed three-dimensional networks, while the copper complex was a one-dimensional network. In consideration of the anhydrous form of the complexes, the thermal stability of the complexes was of the following order: Co (273°C) > Cu (229°C) > Cd (175°C) > Mn (167°C).