Design and synthesis of novel heterocyclic pivalamide ligands and their copper(II) complexes: Structure, BSA/DNA interactions and SOD synzyme activity

Abstract

Four new heterocyclic pivalamide based ligands (L1-L4) and their respective mononuclear copper(II) complexes (C1 = [Cu(N-(thiazol-2-yl)pivalamide)2], C2 = [Cu(N-(5-methylthiazol-2-yl)pivalamide)2], C3 = [Cu(N-(benzothiazol-2-yl)pivalamide)2], C4 = [Cu(N-(benzoimidazol-2-yl)pivalamide)2]) were synthesized to serve as low molecular weight SOD mimics. The complexes were characterized by single crystal XRD, Hirshfeld surface analysis, FT-IR, UV–vis, EPR and ESI-MS studies. C1 crystallizes out in a triclinic system with P-1 space group, while C2 and C4 belong to P21/c and P21/n space groups respectively, from monoclinic system. The crystal structures indicate nearly square planar geometry where mononuclear copper(II) metal ions have coordinated with O and N donor atoms of the pivalamide ligands in trans fashion. All the complexes can scavenge superoxide concentration at low concentrations, in the order C2 < C3 < C1 < C4. The interaction of all the complexes with BSA (bovine serum albumin) protein investigated using fluorescence titration method indicated a static quenching mechanism (KBSA values of the order 105 M−1). The ability of the complexes to bind with calf thymus DNA were also evaluated using absorption and fluorescence titration methods and an intercalative interaction mode of the complexes with DNA was established (Kb values of the order 104 M−1). The complexes have a strong ability to cleave supercoiled plasmid DNA.