Spectral and structural studies of nickel(II) complexes of salicylaldehyde 3-azacyclothiosemicarbazones

Mononuclear nickel(II) complexes with two ONS donor thiosemicarbazone ligands {salicylaldehyde 3-hexamethyleneiminyl thiosemicarbazone [H2L1] and salicylaldehyde 3-tetramethyleneiminyl thiosemicarbazone [H2L2]} have been prepared and physico-chemically characterized. IR and electronic spectra of the complexes have been obtained. The thiosemicarbazones bind to the metal as dianionic ONS donor ligands in all the complexes except in [Ni(HL1)2] (1). In compound 1, the ligand is coordinated as a monoanionic (HL−) one. The magnetic susceptibility measurements indicate that all the complexes are mononuclear and are diamagnetic. The complexes were given the formulae [Ni(HL1)2] (1), [NiL1py] (2), [NiL1α-pic] (3), [NiL1γ-pic] · H2O (4), [NiL2py] (5) and [NiL2γ-pic] (6). The structures of compounds 2 and 3 have been solved by single crystal X-ray crystallography and were found to be distorted square planar in geometry with coordination of azomethine nitrogen, thiolato sulfur, phenolato oxygen and pyridyl nitrogen atoms.

Graphical abstractFour nickel(II) complexes of salicylaldehyde N(4)-hexamethyleneiminyl thiosemicarbazone (H2L1) and two nickel(II) complexes of salicylaldehyde N(4)-pyrrolidine thiosemicarbazone (H2L2) have been synthesized and characterized by different physicochemical techniques. The complexes were given the formulae [Ni(HL2)2] (1), [NiL2py] (2), [NiL2α-pic] (3), [NiL2γ-pic] · H2O (4), [NiL4py] (5) and [NiL4γ-pic] (6). In complex 1, the ligand moieties are coordinated as monoanionic (HL−). The other complexes posses the stoichiometry NiLB, where B represents different bases, viz. pyridine and α/β/γ-picoline. The coordination geometry around nickel(II) in 2 and 3 is found to be distorted square planar in geometry with coordination of azomethine nitrogen, thiolato sulfur, phenolato oxygen and pyridyl nitrogen atoms.Figure optionsDownload full-size imageDownload as PowerPoint slide