Synthesis, characterization and interaction of a new chiral trinuclear complex [bis(aquodiaminotryptophanato) CuII-Sn2IV]chloride with calfthymus DNA

The new chiral trinuclear complex, [bis(aquodiaminotryptophanato)Cu-II-Sn-2(IV)] chloride (1) was synthesized by employing a well-designed three-step pathway under anhydrous conditions. Interaction of the complex (1) with calf-thymus DNA was studied by spectrophotometry, cyclic voltammetry and viscosity measurements. The kinetic studies of calf-thymus DNA binding were carried out at 260 nm (lambda(max) of calf-thymus DNA) under pseudo-first order conditions. The rate constants, k(obs), were evaluated by the linear least squares regression method. The absorption spectra of the complex with calf-thymus DNA shows 'hyperchromism' which is attributed to the electrostatic interaction with calf-thymus DNA. The electrochemical behavior of complex (1) was studied in DMSO/H2O (5:95) solution and showed a quasireversible Cu-II/Cu-I redox couple. The voltammetric studies of the complex in the absence and in the presence of DNA exhibit a shift in the formal potential E-0 and ratio of cathodic to anodic peak currents i(pa)/i(pc) indicating strong binding of the complex to calf-thymus DNA. The viscosity of DNA decreases with increasing concentration of the complex, suggesting that complex (1)binds to calf-thymus DNA by electrostatic association.