6533b873fe1ef96bd12d4ba3

RESEARCH PRODUCT

Organometallic complexes with biological molecules, IV. Di- and tri-organotin(IV) amoxicillin derivatives: Solid-state and solution-phase spectroscopic investigations

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Novel di- and tri-organotin(IV) derivatives of amoxicillin (amoxicillin - =Amox - =6-[D(-)-β-amino-p-hydroxyphenylacetamido] penicillinate) have been prepared. The isolated compounds showed stoichiometries of the type R 2 SnClAmox.2H 2 O, R 3 SnClAmoxNa.2H 2 O and R 2 SnAmox 2 .2H 2 O (R=Me, Bu, Ph). The infrared spectra suggest that Amox − , in both R 2 SnClAmox.2H 2 O and R 2 SnAmox 2 .2H 2 O, behaves as a monoanionic bidentate ligand, coordinating the tin(IV) atom through the ester-type carboxylate, as well as through the lactamic carbonyl. In R 3 SnClAmoxNa.2H 2 O, Amox - coordinates the organotin(IV) moieties through the lactamic carbonyl. In all of the compounds, water molecules are not involved in coordinaton, as inferred by thermogravimetric (TG) investigation. In both R 2 SnClAmox.2H 2 O and R 3 SnClAmoxNa.2H 2 O, trigonal bipyramidal configrations are proposed in the solid state, on the basis of infrared (IR) and Mossbauer spectroscopy, while in R 2 SnAmox 2 .2H 2 O the coordination geometry at tin could be a skew-trapezoidal bipyramid, with two chelating amoxicillin residues which act as bidentate ligands in the trapezoidal plane, and with the organic groups in axial positions. The C-Sn-C angles calculated from the experimental Mossbauer quadrupole splitting predict a bent skeleton in all the R 2 SnAmox 2 2H 2 O derivatives. 1 H and 13 C NMR measurements showed that both R 2 SnClAmox.2H o and R 2 SnAmox.2H 2 O are stable in DMOS-d 6 solutions, maintaining their solid-state configuration, while R 3 SnClAmoxNa.2H 2 O dissociates. Coordination hypotheses have been checked through the correlation between the Mossbauer isomer shift (δ) and the partial atomic charge on tin atoms (Q Sn ) performed, for all the new organotin(IV) compounds, on the basis of an equalization procedure applied to idealized trigonal bipyramidal structures for R 2 SnClAmox.2H 2 O and R 3 SnClAmoxNa.2H 2 O and octahedral trans-R 2 for R 2 SnAmox 2 .2H 2 O