Published Paper Details:

The present investigation describes the synthesis of a novel macrocyclic ligand obtained through the condensation of benzyl and oxalyldihydrazide in a methanolic medium under reflux conditions. The reaction yields a stable, crystalline macrocycle containing both nitrogen and oxygen donor centers capable of coordinating with transition metal ions. The ligand was subsequently allowed to react with divalent cobalt, nickel, and copper salts in the presence of chloride, nitrate, and acetate anions, resulting in a series of metal complexes of the general formula [M(C??H??N?O?)X?], where M = Co(II), Ni(II), Cu(II) and X = Cl?, NO??, or OAc?. Comprehensive analytical and physicochemical studies were carried out to confirm the composition and structural features of the synthesized ligand and its complexes. Elemental analysis and molecular weight determination verified the proposed stochiometry, while molar conductance measurements indicated their non-electrolytic or weakly electrolytic nature depending on the coordinating anion. The magnetic susceptibility data, together with electronic spectral transitions, provided valuable insight into the electronic environment of the metal ions and strongly suggested the formation of six-coordinate octahedral complexes. Spectroscopic investigations--including infrared, far-infrared, UV-Visible, and proton NMR studies--revealed significant shifts in characteristic vibrational and electronic bands, confirming the coordination of metal ions through azomethine nitrogen and carbonyl oxygen atoms of the macrocyclic framework. Infrared spectra displayed lowering of C=N and C=O stretching frequencies upon complexation, supporting metal-ligand bond formation, while far-IR spectra provided additional evidence through metal-nitrogen and metal-oxygen vibrational bands. The UV-Vis spectra exhibited characteristic d-d transitions consistent with octahedral geometry for Co(II), Ni(II), and Cu(II) complexes. Overall, the combined spectral, magnetic, and analytical data conclusively establish the formation of stable, six-coordinate octahedral complexes of the synthesized macrocyclic ligand with Co(II), Ni(II), and Cu(II) ions. The study highlights the strong chelating ability of the ligand, the influence of anions on coordination behavior, and the potential applications of such macrocyclic complexes in catalysis, bioinorganic modelling, and material science.