New Dihydro OO′Bis(Salicylidene) 22′ AminobenzothiazolylBorate Complexes: Kinetic and Voltammetric Studies ofDimethyltin Copper Complex with Guanine Adenine and CalfThymus DNA

摘要

The newly synthesized ligand, dihydro OO′bis(salicylidene) 2,2′ aminobenzothiazolyl borate (2), was derived from the reaction of Schiff base of 2-aminobenzothiazole and salicylaldehyde with KBH4. Cu^II (3) and Zn^II (4) complexes of (2) were synthesized and further metallated with dimethyltindichloride to yield heterobimetallic complexes (5) and (6). All complexes have been thoroughly characterized by elemental analysis, and IR, NMR, EPR, and UV-Vis spectroscopy and conductance measurements. The spectroscopic data support square planar environment around the Cu^II atom, while the Sn^IV atom acquires pentacoordinate geometry. The interaction of complex (5) with guanine, adenine, and calf thymus DNA was studied by spectrophotometric, electrochemical, and kinetic methods. The absorption spectra of complex (5) exhibit a remarkable “hyperchromic effect” in the presence of guanine and calf thymus DNA. Indicative of strong binding of the complex to calf thymus DNA preferentially binds through N7 position ofguanine base, while the adenine shows binding to a lesser extent.The kinetic data were obtained from the rate constants, kobs,values under pseudo-first-order conditions. Cyclic voltammetry wasemployed to study the interaction of complex (5) with guanine,adenine, and calf thymus DNA. The CV of complex (5) in theabsence and in the presence of guanine and calf thymus DNA altereddrastically, with a positive shift in formal peak potentialEpa and Epc values and a significant increase in peakcurrent. The positive shift in formal potentials with increase inpeak current favours strong interaction of complex (5) with calfthymus DNA. The net shift in E1/2 has been used to estimatethe ratio of equilibrium constants for the binding ofCu(II) and Cu(I) complexes to calf thymus DNA.