DNA interaction and cleavage studies of ancillary chiral ligand and N,N-donor ligands coordinated platinum(II) complexes

摘要

Four new platinum(II) complexes [Pt(dpen)(bpy)](ClO4)(2) (1), [Pt(dpen)(phen)] (ClO4)(2) (2), [Pt(dpen)(dpq)](ClO4)(2) (3) and [Pt(dpen)(dppz)](ClO4)(2) (4) comprising of different N,N-donor ligands, viz., 2,2'-bipyridine (bpy), 1, 10-phenanthroline (phen), dipyridoquinoxaline (dpq), dipyrido-[3,2-d:2(sic),3(sic)-f-phenazine] (dppz), and chiral ancillary ligand 1R, 2R-1,2-diphenylethylenediamine (dpen) have been synthesized and characterized. The interaction of these complexes 1-4 with calf-thymus DNA (CT-DNA) has been explored using absorption, circular dichroism spectral and cyclic voltammetric studies. The absorption spectrum of complex 4 with dppz ligand exhibits a major red shift with an overall hypochromic as well as a hyperchromic effect in the presence of DNA, other complexes (1-3) show only hypochromism. From these absorption spectral studies, the intercalative ability of the complexes follows the order as, 4 3 2 1, which is further confirmed by CD and cyclic voltammetry measurements. CD spectral studies show that DNA becomes more A-like upon interaction with the complexes 1 & 2 but the complexes 3 & 4 bring about B-form to Z-form DNA conformational transition. The DNA cleavage study of these Pt(II) complexes 1-4 carried out by gel electrophoresis revealed that complexes 1-4 can cleave super coiled (SC) pUC18 DNA efficiently into open circular form (form II) under hydrolytic and oxidative conditions.