Tin-119 ‘Mössbauer titration’ of dimethyl- and trimethyl-tin(IV) hydroxides with model ligands mimicking nucleic acid phosphate sites, and with deoxyribonucleic acid

Abstract

Aqueous systems at pH 7.4, consisting respectively of phosphate, D-ribose 5-phosphate, dimethylphosphinate, adenosine 3′ : 5′-cyclic monophosphate (Ado-3′ : 5′-P), and native DNA, as well as of either SnMe₂(OH)₂or SnMe₃(OH)(OH₂), have been investigated by ¹¹⁹Sn Mössbauer spectroscopy, on samples frozen at 77.3 K. The trends in the variation of the Mössbauer parameters, as a function of the molar ratio ligand group: metal, have been determined for each system. The results are interpreted in terms of complex formation, which appears to be rather consistent for phosphate and D-ribose 5-phosphate with respect to both organotins. The effect due to dimethylphosphinate and Ado-3′ : 5′-P is quite limited, in a special way towards SnMe₃(OH)(OH₂), and native DNA does not induce any interaction. The distorted ‘average’ configuration of the organotin moieties, as well as the nature of the complex species determining the distortions, have been inferred through the rationalization of the experimental nuclear quadrupole splittings by application of the point-charge model.