ORGANOTIN COMPOUNDS AND DEOXYRIBONUCLEIC-ACID

The interaction of organotin(IV) moieties Sn(IV)R2 and Sn(IV)R2 (R = Me, Et, Bu(n), C8H17 or Ph) with calf thymus deoxyribonucleic acid (DNA) has been studied. The experimental conditions have been determined for the formation of condensates Sn(IV)R2- and Sn(IV)R3-DNA by the reaction of ethanolic organotins [SnR2Cl2(EtOH)2 and SnR3Cl(EtOH)], as well as aqueous Sn(IV)Me3 species, with aqueous DNA. The nature of the condensates has been investigated by Sn-119 Mossbauer spectroscopy. The species SnEt2(DNA phosphate)2 and SnR3(DNA phosphate) (R = Me or Et) have been assumed to occur, where the environment of the tin atoms would be trans octahedral and trigonal bipyramidal respectively. In the reaction with aqueous DNA of SnR2Cl2(EtOH)2 and SnR3Cl(EtOH) (R = Bu(n), C8H17 or Ph), stannoxanes (SnR2Cl)2O and hydroxides SnR3(OH) would form too, being possibly the main reaction products for the moieties Sn(IV)(C8H17)2, Sn(IV)(C8H17)3 and Sn(IV)Ph3. Possible bonding situations have been advanced for Sn(IV)R(n)-DNA condensates, involving e.g. two vicinal phosphodiester groups (from the DNA double strand) cis-co-ordinated giving an octahedral geometry, as well as a phosphodiester residue axially binding Sn(IV)R3 to give a trigonal-bipyramidal structure.