Mn(II) complexes of 1-(4-methoxybenzoyl)-4-phenyl-3-thiosemicarbazide containing o-phenanthroline and 2,2-bipyridine as co-ligands: Synthesis, crystal structure, spectral characterization, photoluminescence and electrochemical studies

Abstract

Here, two complexes [Mn(Hmpth)2(bpy)] (1) and [Mn(Hmpth)2(o-phen)](2) with 1-(4-methoxybenzoyl)-4-phenyl-3-thiosemicarbazide (H2mpth) have been synthesized which contains 2-2′-bipyridine (bpy)/ o-phenanthroline (o-phen) as co-ligand. The ligand, H2mpth and its Mn(II) complexes have been characterized by IR, NMR, magnetic behaviour and single crystal X-ray data. In both complexes, the metal ions adopt a distorted octahedral geometry. Here, role of co-ligands (2,2-bpy and o-phen) on the optoelectronic properties of Mn(II) complexes is investigated for the first time. Complex 1 exhibits high fluorescence intensity as compared to ligand H2mpth and complex 2. The order of fluorescent behaviour found as complex 1 > complex 2 > H2mpth. Thermal behaviour of complexes were also studied. The electrochemical characteristics of Mn(II) complexes is studied using cyclic voltammetry technique after immobilizing it on the glassy carbon electrode modified with Nafion-multi-walled carbon nanotubes. The cyclic voltammetry studies indicate a reversible one electron transfer process corresponding to the Mn2+/3+ redox processes.