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

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-carboxaldehyde with benzhydrazide, 4-methoxybenzhydrazide and 4-dimethylaminobenzhydrazide, 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 P2(1)/n with a = 9.836(3), b = 23.994(7), c = 10.222(3) Angstrom, beta = 104.14(3)degrees, V = 2339.5(13) Angstrom(3) and Z = 4. In the distorted octahedral MnN4O2 coordination sphere each ligand acts as a meridional N,N,O donor utilising pyridine-N, imine-N 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 (5.88-6.12 mu(B)) of the complexes are consistent with a high-spin d(5) system. EPR spectra of the complexes suggest a similar distorted octahedral N4O2 coordination sphere around Mn(II) in each complex.