Synthesis, structure and properties of manganese(II) complexes with aroylhydrazones of 2-pyridine-carboxaldehyde

Abstract

Manganese(II) complexes of terdentate N,N,O donor Schiff bases (HL) are described. The ligands Hpabh, Hpamh and Hpadh are obtained by condensing 2-pyridine-carboxaIdehyde with benzhydrazide, 4-methoxybenzhydrazide and 4-dimethyIaminobenzhydrazide, respectively. The reaction of HL with manganese(II) acetate tetrahydrate affords [MnL2]. The crystal structure determination of [Mn(pabh)2] was performed. The complex crystallises in the space group P21/n with a = 9.836(3), b = 23.994(7), c = 10.222(3)Å, β= 104.14(3)°, V = 2339.5(13)Å3 and Z = 4. In the distorted octahedral MnN4O2 coordination sphere each ligand acts as a meridional N,N,O donor utilising pyridine-N, imine-W and amide-O atoms. Electronic spectra of the complexes display charge transfer bands in the range 404-298 nm. Room temperature solid state magnetic moments (5.88-6.12μB) of the complexes are consistent with a high-spin d5 system. EPR spectra of the complexes suggest a similar distorted octahedral N4O2 coordination sphere around Mn(II) in each complex.