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Non-enolisable Knoevenagel condensate appended Schiff bases-metal (II) complexes: Spectral characteristics, DNA-binding and nuclease activities

Overview of Gubendran A et al.

AuthorsGubendran A  Kesavan MP  Ayyanaar S  Mitu L  Athappan P  Rajesh J  
AffiliationDepartment of Inorganic Chemistry   School of Chemistry   Madurai Kamaraj University   Madurai 625 021   India; Chemistry Research Centre   Mohamed Sathak Engineering College   Kilakarai 623 806   Tamilnadu   India. Electronic address: mkuraji@gmail.com.  
JournalSpectrochim Acta A Mol Biomol Spectrosc
Year 2017

Abstract


New Schiff base complexes [Cu(L(1))Cl] (1), [Ni(L(1))Cl] (2), [Zn(L(1))Cl] (3), and [Fe(L(2))H(2)OCl] (4) {L(1)=(4E)-3-(2-hydroxybenzylidene)-4-(2-hydroxyphenylimino)pentan-2-one, L(2)=2,2'-(1E,1'E)-(3-(2-hydroxybenzylidene)-pentane-2,4-diylidene)bis(azan-1-yl-1 idene)diphenol} have been synthesized and characterized by elemental analysis, UV-Vis, IR, FAB-mass, EPR, spectral studies and electrochemical studies, the ligands L(1) &L(2) were characterized by (1)H and (13)C NMR spectra. Complex 1 show a visible spectral d-d band near 600nm and display cyclic voltammetric quasireversible response for the Cu(II)/Cu(I) couple vs Ag/AgCl in DMSO. The EPR spectrum of 1 show g(‖)>g(⊥) suggesting a square planar geometry around copper with d(x)(2)(-)(y)(2) as the ground state. The mass spectral results have confirmed the proposed structure for complexes 1-4. DNA binding properties of these complexes 1-4 have been investigated by absorption titrations, cyclic voltammetric studies and circular dichroism studies. On titration with DNA, the complexes 1-4 show hypochromism at the MLCT band (13-31%) with a red shift of 1-8nm in the electronic spectrum and positive shift of voltammetric E(1/2) in the CV studies are in favour of intercalative binding. CD spectra of 1 showed an increase in molar ellipticity (θ(278)) of the positive band with a minor red shift indicating the transition of B-form of DNA to A like form. DNA cleavage studies of complexes 1 and 4 with pUC18 DNA were studied by gel electrophoresis and complex 4 cleaves supercoiled pUC18 DNA in an oxidative manner in the presence of H(2)O(2) and on photo irradiation at 312nm.