Design, structural elucidation, DNA interaction and antimicrobial activities of metal complexes containing tetraazamacrocyclic Schiff bases

Abstract

Tetraazamacrocyclic Schiff bases, designed and synthesized from 3-hydroxy-4-nitrobenzylideneacetoacetanilide/3-hydroxy-4-nitrobenzylidene-o-acetoacetotoluidide and 1,2-diaminobenzene, are tetradentate ligands and form solid cationic complexes with CuII, NiII, CoII, ZnII, MnII, and VOIV salts in ethanol. Microanalytical data, magnetic moment, electronic, IR, Mass, 13C NMR, IH NMR, and electron spin resonance (ESR) techniques were used to characterize the synthesized compounds. Electronic absorption and IR spectra suggest that all the complexes are square planar, while the oxovanadium complexes are square pyramidal. Elemental analyses and mass spectra suggest that the general formula of the complexes is [ML]X (where L = L1 or L2, X = 2Cl− or ). Electrolytic behavior of the chelates was assessed from conductance data. The X-band ESR spectra of copper and oxovanadium complexes, recorded in dimethyl sulfoxide at 300 and 77 K, are discussed. Binding of the metal complexes with DNA has been investigated by spectroscopic, viscometric, and voltammetric methods. These data suggest that the complexes interact with DNA by intercalative binding. A comparative study of minimum inhibitory concentration values of the ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands. The nuclease activity shows that the copper, manganese, nickel, and vanadium complexes cleave DNA through redox chemistry.