Spectroscopic, DFT, optical band gap, powder X-ray diffraction and bleomycin-dependant DNA studies of Co(II), Ni(II) and Cu(II) complexes derived from macrocyclic Schiff base

Macrocyclic nitrogen ligand, (2E)-3,6,10,13-tetramethyl-2,7,9,14-tetraaza-1,8 (1,4)-dibenzena cyclotetradecaphane-2,6,9,13-tetraene (PDHDH) as well as its Co(II), Ni(II) and Cu(II) complexes were isolated and characterized by conventional methods. The morphology of the Cu(II) complex was further studied by X-ray powder diffraction. The complexes assigned the general formulae: [M(PDHDH)Cl-2]Cl center dot mH(2)O (m = 5.5 for Co(II), 3 for Ni(II) and 8 for Cu(II), respectively adopting a distorted octahedral structure on the basis of magnetic and electronic spectral data with N-4 tetradentate donor sites and two Cl atoms occupying the other two sites. ESR spectrum was displayed and the Hamiltonian parameters were evaluated. The geometry, HOMO, LUMO, polarizability and other energetic parameters were evaluated by DFT theory on Material Studio package. The thermal decomposition of the compounds and associated kinetic parameters employing Coats-Redfern and Horowitz-Metzger methods were determined. Optical band gap (E-g) has been estimated as well; revealing that Cu complex has the largest energy gap and considered as a highly efficient photovoltaic material. Further, the compounds were screened for in vitro against pathogenic bacteria and Bleomycin-dependant DNA assay was indicating the good inhibition of the title compounds against Gram-positive strains than the Gram-negative bacteria and they hold some protective effect on DNA by a particular mechanism. (C) 2018 Elsevier B.V. All rights reserved.