Pseudohalide-induced structural variations in hydrazone-based metal complexes: Syntheses, electrochemical studies and structural aspects

The effects of pseudohalides on the modes of binding of a hydrazone ligand are investigated and we report here four new hydrazone complexes [Co(L) 2 ] · ClO 4 ( 1 ), [Co(L) 2 ] 2 [Co(SCN) 4 ] ( 2 ), [Mn(L) 2 ] ( 3 ) and [Mn(N 3 ) 2 ( LH ) 2 ] · H 2 O ( 4 ) [where LH = condensation product of pyridine-2-carboxaldehyde and benzhydrazide]. The hydrazone ligand is quite diverse in its chelating ability and can act as a neutral or mononegative ligand and as a bidentate or tridentate unit. In this paper, we report structures showing different denticities of the ligand having different charges. The complexes are characterized by IR, UV–Vis spectroscopy and cyclic voltammetric studies and the structures are conclusively established by single crystal X-ray diffraction study. Of the complexes, 1 and 3 are purely metal hydrazone complexes whereas 2 and 4 incorporate coordinated pseudohalides in their crystal structures, and 4 shows different coordination modes of the hydrazone ligand.