Organometallic complexes with biological molecules. XVIII. Alkyltin(IV) cephalexinate complexes: synthesis, solid state and solution phase investigations

Dialkyltin(IV) and trialkyltin(IV) complexes of the deacetoxycephalo-sporin-antibiotic cephalexin [7-(D-2-amino-2-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid] (Hceph) have been synthesized and investigated both in solid and solution phase. Analytical and thermogravimetric data supported the general formula Alk(2)SnOHceph . H2O and Alk(3)Snceph . H2O (Alk = Me, n-Bu), while structural information has been gained by FT-IR, Sn-119 Mossbauer and H-1, C-13, Sn-119 NMR data. In particular, IR results suggested polymeric structures both for Alk(2)SnOHceph . H2O and Alk(3)Snceph . H2O. Moreover, cephalexin appears to behave as monoanionic tridentate ligand coordinating the tin(IV) atom through ester-type carboxylate, as well as through beta-lactam carbonyl oxygen atoms and the amino nitrogen donor atoms in Alk(2)SnOHceph . H2O complexes. On the basis of Sn-119 Mossbauer spectroscopy it could be inferred that tin(IV) was hexacoordinated in such complexes in the solid state, showing skew trapezoidal configuration. As far as Alk(3)Sn(IV)ceph . H2O derivatives are concerned, cephalexin coordinated the Alk(3)Sn moiety through the carboxylate acting as a bridging bidentate monoanionic group. Again, Sn-119 Mossbauer spectroscopy led us to propose a trigonal configuration around the tin(IV) atom, with R3Sn equatorial disposition and bridging carboxylate oxygen atoms in the axial positions. The nature of the complexes in solution state was investigated by using H-1, C-13 and Sn-119 NMR spectroscopy. Finally, the cytotoxic activity of organotin(IV) cephalexinate derivatives has been tested using two different chromosome-staining techniques Giemsa and CMA(3), towards spermatocyte chromosomes of the mussel Brachidontes pharaonis (Mollusca: Bivalvia). Colchicinized-like mitoses (c-mitoses) on slides obtained from animals exposed to organotin(IV) cephalexinate compounds, demonstrated the high mitotic spindle-inhibiting potentiality of these chemicals. Moreover, structural damages such as 'chromosome achromatic lesions',,chromosome breakages' and 'chromosome fragments' have been identified through a comparative analysis of spermatocyte chromosomes from untreated specimens (negative controls) and specimens treated with the organotin(IV) complexes.