A study of dimethyltin(IV)‐L‐cysteinate in aqueous solution

Abstract

The in vivo activity of some R,Sn-L-cysteinate complexes (R = Me, Et, n-Bu) against murine P-388 leukaemia has been tested. Only the Et,Sn(IV) complex showed a marginal positive effect. Trigonal bipyramidal tin environments with two carbon (R) atoms and the sulfur atom in the equatorial plane and oxygen (carboxylate) and nitrogen (NHJ in apical positions have been proposed for the solid compexes (R = Me, Et, n-Bu, Ph) on the basis of experimental Mossbauer parameters and infrared (IR) data. Aqueous solutions of the Me&-Lcysteinate have been studied by IR, 'H NMR and '19Sn Mossbauer spectroscopy (in frozen solution) at different pH values to identify the Me,Sn(IV) species present. At pH > 2 the dimethyltin aquocation is complexed by the ionized sulfhydryl group of L-cysteine to form a five-coordinated species. With increasing pH values, NH: is deprotonated and a chelate is proposed with both the sulfhydryl and the amino group bonded to tin, one water molecule or (at still higher pH values) one hydroxyl ion occupying the fifth coordination site of a trigonal bipyramid around tin. Finally at pH > 10 the NH, group is substituted by a hydroxyl ion.

Thermodynamic and spectroscopic study for the interaction of dimethyltin(IV) with L–cysteine in aqueous solution

“…The formation of MLH species in the acidic pH range (2≤pH≤4) is confirmed by the results obtained for the same system by Buzás et al, Silvestri et al [18,19] and in the system…”

“…4 interaction of the organotin moieties with several biologically relevant compounds such as carbohydrates, amino acids, peptides, nucleic acids and DNA has been carried out mostly in the last decade [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. From some of these cited studies, the interaction of dimethyltin (IV) and trialkyltin(IV) (with R = methylic, ethylic, and butylic groups) in aqueous solution, at physiological pH, with thiol groups of model molecules, as well as feline and rat haemoglobin, have been investigated by 119 Sn Mössbauer spectroscopy.…”

“…Spectroscopic studies on the characterization of several organotin(IV) derivatives of cys [17,18]; potentiometric [19,20] and Mössbauer [19] investigations on the coordination of cys and its derivatives towards trialkyltin(IV) cations can be found in literature.…”

“…It is worth to mention that Silvestri et al [18] studied the system dimethyltin(IV)-cys in aqueous solution by means of 1 H NMR, not considering the fast mutual exchange occurring in the experimental conditions. Furthermore some small signals clearly associated to the presence of low amount of cystine were wrongly ascribed to cys-containing species.…”

Computational study of dimethyl‐ and trimethyl‐tin(IV) complexes of porphyrin derivatives

“…These latter interactions would not seem able to induce substantial modifications to the DNA and hence could not explain the dramatic toxicity of the tin(IV) moieties. However, it is known that diorgano-and triorgano-tin(IV) compounds make stable complexes with biological ligands 13,14 containing oxygen, sulfur and nitrogen donor atoms and, it is likely that the observed biological activity of the organotin(IV) compounds could be modulated by the presence of these ligands.…”