Spectroscopic and X-ray structural characterization of new organotin carboxylates and their in vitro antifungal activities

Abstract

The reactions of SnR2Cl2 (R = Me, Bu or Ph) with sodium 4-phenylbutyrate, NaO2C(CH2)3Ph (NaOPhb), yielded three organotin carboxylates, namely [{(Me2SnOPhb)2O}2] (1), [Bu2Sn(OPhb)2] (2) and [{PhSn(O)OPhb}6] (3). Complexes (1) and (2) have been spectroscopically authenticated by FT-IR, 119Sn Mössbauer, and 1H, 13C{1H} and 119Sn{1H} NMR techniques. In addition, the crystallographic structures of (1)-(3) have been determined by X-ray diffraction measurements. Complex (1) displays two signals in the solution 119Sn NMR spectrum corresponding to the exo (δ -176.3) and endocyclic (δ -188.4) SnMe2 moieties, whereas (2) exhibits only one 119Sn resonance (δ -148.1). The crystallographic characterization of (1) confirms the centrosymmetric tetranuclear stannoxane structure and the existence of the exo and endocyclic SnMe2 moieties in the both distorted trigonal bipyramidal and octahedral environment, respectively. Complex (2) crystallises as a monomer in which the Sn(IV) cation lies at the centre of a distorted octahedron. The bonding scheme in (3) outlines a hexanuclear drum-like structure comprising two six-membered (-Sn-O-)3 stannoxane rings. The supramolecular arrangements of (1)-(3) result from noncovalent interactions, namely SnO (1) and (2), C-Hπ (1), and C-HO (1)-(3). Finally, antifungal activities of all organotin derivatives have been screened against Candida albicans (ATCC 18804), Candida tropicalis (ATCC 750), Candida glabrata (ATCC 90030), Candida parapsilosis (ATCC 22019), Candida lusitaniae (CBS 6936), and Candida dubliniensis (clinical isolate 28). Complex (2) exhibited the best biocide activity amongst the three organotin products. © 2016 Elsevier Ltd. All rights reserved.