Copper hydrazone complexes with different nuclearties and geometries: Synthesis, characterization, single crystal structures, Hirshfeld analysis and superoxide dismutase mimetic activities

Three new copper(II) hydrazone complexes [Cu(L)(neocuproine)]NO3 1, [Cu(L)(6-benzylaminopurine)ClO4] 2 and [Cu(L)μ(1,1-N3)Na(H2O)2] 3 with different nuclearties and geometries using acetic acid(2‑hydroxy-3‑methoxy-benzylidene)-hydrazide (HL) as proligand and neucuproine, 6-benzylaminopurine and sodium azide as co-ligands have been synthesized and characterized using several physico-chemical and spectral methods. Molecular structures of complexes were obtained by single crystal diffraction technique. The coordination sphere in complexes 1 and 2 can be illustrated as distorted square pyramidal geometry whereas 3 has distorted square planar geometry. Supramolecular structures were formed via different intermolecular interactions like hydrogen bondings and CH⋯π in 1, hydrogen bondings, CH⋯π and lp⋯π in 2 and hydrogen bondings, CH⋯π, lp⋯π and π⋯π(chelate-chelate) interactions in 3. The Hirshfeld surface analysis exhibited O⋯H, N⋯H and C⋯H interactions in all complexes. The optimized geometry of newly synthesized complexes were obtained by B3LYP/LANL2DZ model. From the differences in energies of frontier molecular orbitals (ΔEg), reactivity parameters like, ionization potential (IP), electron affinity (EA), electronegativity (χ), softness (S), hardness (η) and electrophilicity index (ω) were determined. In these complexes the Epr parameters (g-) showed the trend g∥>g⊥>2.0023, which is consistent with a dx2−y2 ground state in a square based geometry. Electrochemical properties also determined using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Additionally, superoxide dismutase catalytic activity measurements were performed by nitro blue tetrazolium chloride (NBT) assay in phosphate buffer. All complexes catalyzed the dismutation of superoxide at biological pH. Enhancement in the SOD activity of 2 can be credited to the coordinated poorly bound ClO4− ion which is easily replaced by O2·− ion.