New dimeric complexes with semicarbazone mannich-based ligand; formation, structural investigation and biological activity

Abstract

The formation of a new semicarbazone Schiff-base ligand (E)-2-(2-(phenyl(2-phenylhydrazinyl)- methyl)cyclohexylidene)hydrazine-1-carboxamide (HL) and its complexes are reported. The new ligand was prepared from the condensation of the Mannich-base 2-(phenyl(2-phenylhydrazinyl)methyl)cyclohexan-1-one (M) with the semicarbazide. A series of metal complexes were prepared by the reaction of the ligand with the metal chlorides of Cr(III), Mn(II), Co(II), Ni(II), Cu(II)), Zn(II) and Cd(II). The structure of the ligand and its complexes were elucidated through analytical and spectroscopic techniques. The analyses indicated the ligand behaves as a monobasic tridentate species and the isolation of dimeric complexes with the general formula; [Cr(L)(Cl)2(H2O)]2, [M(L)Cl]2 (where M= Mn(II), Co(II), Ni(II), Cu(II)), Zn(II) and Cd(II)). These studies revealed a distorted octahedral geometry for Cr(III), a distorted square planar for Cu(II) and a tetrahedral arrangement for Mn(II), Co(II), Ni(II), Zn(II) and Cd(II). The biological activity of the prepared compounds against Escherichia coli, Pseudomonas auroginosa, Staphylococcus aureus and Bacillus subtilis compared with Cefotaxime (as a standard antibiotic) was also explored. Some of the examined compounds indicated a similar antibacterial activity to Cefotaxime. Furthermore, antifungal activity against Candida albicans and Rhizopus sporium was investigated, which showed that the ligand and its complexes exhibited good antifungal activity. Keywords: Schiff-base ligand; Structural characterization; Dimeric semicarbazone complexes; Biological activity.