Synthesis, characterisation, thermal properties and biological activity of coordination compounds of novel selenosemicarbazone ligands

Abstract A series of novel metal complexes with bidentate selenosemicarbazone Schiff-base ligands HL1 and HL2 are reported. The reaction of 2-(((3-nitrophenyl)amino)(phenyl) methyl)cyclohexan-1-one and 2-((4-methoxyphenyl)(phenylamino)methyl)cyclohexan-1-one with an ethanolic mixture of KSeCN and NH2NH2 afforded the preparation of the new selenosemicarbazone ligands (E)-2-(2-(((3-nitrophenyl) amino)(phenyl)methyl)cyclohexylidene)hydrazine-1-carboselenoamide (HL1) and (E)-2-(2-((4-methoxyphenyl)(phenylamino)methyl)cyclohexylidene)hydrazine-1-carboselenoamide (HL2), respectively. The reaction of ligands with Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) metal ions resulted in the formation of mononucleating complexes of general formula K2[ML2Cl2] and [M'L2], (M = Mn(II), Co(II) and Ni(II); M' = Cu(II), Zn(II) and Cd(II)). The mode of bonding and predicted geometry of complexes were determined through their physico-chemical and spectroscopic measurements. These data indicated the formation of the following; (i) a distorted octahedral geometry about Mn(II), Co(II) and Ni(II), (ii) a distorted square planar around Cu(II), and (iii) a tetrahedral arrangement about Zn(II) and Cd(II) ions. The thermal properties and biological activity of ligands and their metal complexes were studied. The title ligands and their metal complexes were screened against Gram negative bacterial strains; Escherichia coli (E. coli), Bacillus sabtuius and Klebsiella pneumoniae and Gram positive bacterial strain Staphylococcus aureus that revealed the metal complexes become more potentially resistive to the microbial activities, compared to the free ligands. Further, selenosemicarbazone ligands and their complexes were examined for their antifungul activity towards Candida albicans, Candida glabrata, Candida tropicalis and Candida parapsilsis, which generally showed complexes are more active compared to the free ligands.