Organometallic complexes with biological molecules: XVII. Triorganotin(IV) complexes with amoxicillin and ampicillin

Abstract

Novel triorganotin(IV) complexes of two β-lactamic antibiotics, 6-[ d-(−)-β-amino- p-hydroxyphenyl-acetamido]penicillin (=amoxicillin) and 6-[ d-(−)-α-aminobenzyl]penicillin (=ampicillin), have been synthesized and investigated both in solid and solution states. The complexes corresponded to the general formula R 3Sn(IV)antib·H 2O (R=Me, n-Bu, Ph; antib=amox=amoxicillinate or amp=ampicillinate). Structural investigations about configuration in the solid state have been carried out by interpreting experimental IR and 119Sn Mössbauer data. In particular, IR results suggested polymeric structures both for R 3Sn(IV)amox·H 2O and R 3Sn(IV)amp·H 2O. Moreover, both antibiotics appear to behave as monoanionic bidentate ligands coordinating the tin(IV) atom through ester-type carboxylate, as well as through the β-lactamic carbonyl. Evidence that in none of these compounds water molecules were involved in coordination, was provided by thermogravimetric investigations. On the basis of 119Sn Mössbauer spectroscopy it can be inferred that tin(IV) was pentacoordinate in all of the complexes in the solid state, showing an equatorial R 3Sn(IV) trigonal bipyramidal (tbp) configuration. The nature of the complexes in solution state was investigated by using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, while an 119Sn spectrum was obtained for n-Bu 3Sn(IV)amp·H 2O. Although 1H- and 13C-NMR measurements suggested that in dimethyl sulfoxide (DMSO)-d 6 solution the polymeric structure collapsed, due to a solvolysis process of the β-lactamic carbonyl bonding to the organometallic moiety, the complexes have been shown to maintain the same trigonal bipyramidal configuration at tin(IV) atom by the coordination of a DMSO molecule. Cytotoxic activity of these novel semisynthetic antibiotic derivatives has been tested towards spermatocyte chromosomes of the mussel Brachidontes pharaonis (Mollusca: Bivalvia) using two different chromosome-staining techniques such as Giemsa and CMA 3. The occurrence of typical colchicinized-like (c-like) mitoses on slides obtained from animals exposed to organotin compounds, directly confirmed the high mitotic spindle-inhibiting potency of these chemicals. In addition, by comparative analysis of spermatocyte chromosomes from untreated specimens (negative controls) and specimens treated with the triorganotin(IV) complexes, structural damages such as ‘achromatic lesions’ and ‘chromosome breakages’ have been identified.