Synthesis and Characterization of Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) Complexes with a New Unsymmetrical Tetradentate N2O2Schiff Base Ligand Driven from 2-Hydroxy-1-Naphthaldehyde and 3,4-Diamino-Benzoic Acid

Five mononuclear complexes containing a new unsymmetrical tetradentateN2O2Schiff base ligand are reported. The ligand, N,N'-bis-(2-hydroxy-1-naphthaldehyde)-3,4-diimino benzoic acid (H2L), was synthesized from the reaction of 3,4-diaminobenzoic acid with 2-hydroxy-1-naphthaldehyde in the presence of glacial acetic acid in methanolic solution. The mononuclear Fe(L), Co(L), Ni(L), Cu(L), and Zn(L) complexes of the Schiff base ligand were synthesized from the reaction of the ligand with the metal salt in the solvent. The complexes were investigated by thermal and elemental analyses, molar conductance, and magnetic susceptibility measurements. Moreover, the ligand (H2L) and its related complexes were characterized using 1H NMR, IR, and UV-Vis spectroscopy. The results of undertaken examinations revealed all the metal complexes formed by the coordination of the N and O atoms of the ligand. Furthermore, the results of molar conductivity measurements indicated the complexes as non-electrolyte species in which the metal center bound to one L2- ligand frame producing four-coordinate-species. Finally, the samples of nickel and zinc complexes were treated at high temperature up to 800 oC where their metal oxides were generated. XRD patterns and SEM images of the resulted oxides confirmed that these complexes might be appropriate entities for preparing nanoparticles.