Synthesis, characterization and binding studies of novel diorganotin(IV) complexes of sodium 2‐mercaptoethanesulfonate

Abstract

Diorganotin(IV) complexes (1‐4) of MESNA (sodium 2‐mercaptoethanesulfonate HSCH2CH2SO3Na) and a mixed ligand complex of dibutyltin(IV), 1,10‐phenanthroline and MESNA (5) were synthesized with thermal and microwave assisted methods. All the complexes were characterized thoroughly with the help of analytical and various spectroscopic techniques viz. FTIR, NMR (1H, 13C, and 119Sn NMR) spectroscopy and ESI‐MS spectrometery. Various spectrophotometric studies were carried out to decipher the binding mode of MESNA and its diorganotin complexes 1‐5 with calf thymus DNA (CT DNA) and thus, to calculate the binding constant (Kb). Absorption spectrophotometric study confirmed the interaction is through partial intercalation of all the complexes including MESNA, inside the DNA helix and calculated binding constant (Kb) is in the order of 103 M‐1. A series of emission spectrophotometric experiments support the results obtained through the absorption spectrophotometric studies. Circular dichroic (CD) spectroscopic analysis and viscosity measurement of CT DNA further complemented the fact that the partial intercalation plays a major role in the interaction of the studied complexes with CT DNA. All the studies corroborated that complex 2 bound to CT DNA with maximum affinity followed by complex 5 among all the complexes. Involvement of hydroxyl radicals as an active species in the cleavage activity of pBR322 plasmid DNA is proved by carrying out agarose gel electrophoretic technique.