Some new metal(II) complexes based on bis-Schiff base ligand derived from 2-acetylethiophine and 2,6-diaminopyridine: Syntheses, structural investigation, thermal, fluorescence and catalytic activity studies

Abstract

A novel Schiff base ligand N, N′-bis (1-(thiophen-2-yl) ethylidene) pyridine-2, 6-diamine has been prepared by the condensation of 2,6-diaminopyridine and 2- acetylthiophene in ethanol in the molar ratio of 1:2. The Study by analytical and spectroscopic techniques indicated that the complexes have composition with the general formulae: [MLX2]· nH2O, where (M = Mn, Co, Ni, and Cu; X = Cl; n = 4, 6, 6, 2), respectively. All the metal (II) complexes have been characterized with elemental analysis, FT−IR, Mass, 1H NMR, UV–Vis, magnetic moment, thermal analysis (TG and DTG) techniques, molar conductance and fluorescence spectra. Non electrolyte of complexes using DMF as a solvent is due to their low molar conductance. From FTIR spectral data, the coordination between the central metal ion with azomethine nitrogen and sulfur of acetylthiophene ring are confirmed. An octahedral geometry of all metal(II) complexes is investigated from electronic and magnetic data. The kinetic analysis of the thermogravimetric data was performed by using the Coats-Redfern equation. The fluorescence properties of theses complexes in DMSO, DMF, and CH3CN were studied. The effect of pH influencing the fluorescence intensity is discussed. The catalytic activities of metal(II) complexes were studied using H2O2 solution.