Isomorphic metal malonates with N-aminoguanidine: MCo2O4 (M = Ni & Zn) nanoparticle synthesis via a (AmgH)2[M1/3Co2/3(mal)2(H2O)2] precursor solid solution

Abstract

Divalent metal complexes of malonate with aminoguanidine possessing (AmgH)₂[M(mal)₂(H₂O)₂] [M = Co (1), Ni (2) or Zn (3); mal = malonate anion and AmgH = aminoguanidinium cation] stoichiometry and their solid solutions, (AmgH)₂[Ni_0.5Co_0.5(mal)₂(H₂O)₂] (4) and (AmgH)₂[M_1/3Co_2/3(mal)₂(H₂O)₂] [where M = Ni (5) or Zn(6)], were prepared and characterized by analytical, thermal and powder X-ray diffraction studies. The crystal and molecular structures of both cobalt and nickel compounds were isomorphic, crystallizing in the triclinic space group P. The complexes exhibit similar modes of endo-followed by exothermic decomposition to produce respective metal oxides below 550 °C. Metal cobaltites, MCo₂O₄ where M = Ni and Zn, were obtained from the above solid solutions as decomposition residues by heating at 600, 700 and 800 °C in a silica crucible for 3 h. Spinel oxides nanoparticles were characterized by infrared spectra, powder X-ray diffraction patterns, scanning electron microscope coupled with energy dispersive X-ray analysis and transmission electron microscope studies.