Structural resemblance and variation in transition metal complexes derived from dipicolinic acid and guanylhydrazine

New aminoguanidinium transition metal dipicolinates of the formula (AgunH)[M-III(dip)(2)]center dot xH(2)O, M = Cr, x = 1.5; Fe, x = 2, (AgunH)(2)[M-II(dip)(2)]center dot nH(2)O, where M = Mn, n = 2; Co or Ni, n = 0 and Zn, n = 1, and [Cu (Agun)(2)][Cu-3(dip)(4)(Agun)(2)]center dot 4H(2)O have been prepared by the reaction of respective metal nitrates with aqueous mixture of dipicolinic acid (H(2)dip) and aminoguanidine bicarbonate (AgunH center dot HCO3) in appropriate mole ratios. These compounds have been characterized by various physico-chemical techniques. Among them Ni, Cu, Cr and Fe complexes have been structurally characterized. The asymmetric units of the Ni and Cr structures contain two independent molecules, whereas Fe has four. Unlike these, the copper compound has a unique structure with a tri-nuclear centrosymmetric anionic complex and cationic bis(aminoguanidine) copper(II). In all of these compounds, the dipicolinate dianion is acting as a tridentate (O, N, O) donor ligand, except copper in-which one of the dipicolinates is tetradentate (O, N, O, O). Cytotoxicity and DPPH scavenging activity studies reveal that the copper complex exhibits superior activity to that of cobalt and nickel. (C) 2017 Elsevier B.V. All rights reserved.