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

Abstract The reactions of SnR 2 Cl 2 (R = Me, Bu or Ph) with sodium 4-phenylbutyrate, NaO 2 C(CH 2 ) 3 Ph (NaOPh b ), yielded three organotin carboxylates, namely [{(Me 2 SnOPh b ) 2 O} 2 ] ( 1 ), [Bu 2 Sn(OPh b ) 2 ] ( 2 ) and [{PhSn(O)OPh b } 6 ] ( 3 ). Complexes ( 1 ) and ( 2 ) have been spectroscopically authenticated by FT-IR, 119 Sn Mossbauer, and 1 H, 13 C{ 1 H} and 119 Sn{ 1 H} 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 119 Sn NMR spectrum corresponding to the exo ( δ −176.3) and endo cyclic ( δ −188.4) SnMe 2 moieties, whereas ( 2 ) exhibits only one 119 Sn resonance ( δ −148.1). The crystallographic characterization of ( 1 ) confirms the centrosymmetric tetranuclear stannoxane structure and the existence of the exo and endo cyclic SnMe 2 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 Sn⋯O ( 1 ) and ( 2 ), C–H⋯π ( 1 ), and C–H⋯O ( 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.