The interaction of S,N-coordinated dimethyltin(IV) derivatives with deoxyribonucleic acid: Structure and dynamics by119Sn mössbauer spectroscopy

Complexes Me2SnCl(SPy) and Me2SnCl(SPym) (HSPy = 2-mercaptopyridine; HSPym = 2-mercaptopyrimidine), from ethanol solutions, interact with aqueous calf-thymus DNA yielding condensed phases with probable Me2Sn(SPy,-SPym) (DNA monomer) stoichiometries of 1:1; the condensation of DNA is inferred originated from electrostatic bonding between complex cations Me2Sn(SPy,SPym)+ and the phosphate oxygen of the phosphodiester groups. Octahedral-or trigonal-bipyramidal tin environments are inferred from the point-charge model treatment of the 119Sn Mössbauer parameter nuclear quadrupole splitting, considering the bonding by S and N, or only S donor atoms from the ligand, as well as possible coordination by H2O molecules. The dynamics of tin atoms in the condensed systems Me2Sn(SPym) (DNA monomer), in both gel and lyophilized phases, have been investigated by variable-temperature 119Sn Mössbauer spectroscopy, obtaining evidence of a general correspondence as reported in the literature for the lyophilized condensates Al-k2Sn(DNA monomer)2; possible analogies for Me2Sn(SPym) (DNA monomer) and Al-k2Sn(DNA monomer)2 in DNA bonding, and structures of tin environments, are discussed. 'Neutral' complexes, such as Me2Sn(SPy)2, neither induce DNA condensation, nor bind to DNA in solution phases. Copyright © 1999 John Wiley & Sons, Ltd.