Synthesis, structural characterization and antimicrobial activity of mixed aryl-alkyl diorganotin(IV) compounds with quinoline-2-carboxylate (L-): {RR'SnLCl}n and RR'SnL2

A series of unsymmetrical diorganotin derivatives of quinoline-2-carboxylic acid (LH), namely polymeric {MePhSnClL}n (1) and {EtPhSnClL}n (2), and mononuclear MePhSnL2 (3) and EtPhSnL2 (4), was synthesized by the reaction of LH with the MePhSnCl2, EtPhSnCl2, MePhSnO, and EtPhSnO precursors, respectively. The compounds were characterized by elemental analysis and infrared spectroscopy, as well as by 1?H, 13?C and 119Sn NMR. The molecular structures of representative compounds 2 and 4 were determined by single-crystal X-ray crystallography. This study showed that polymeric 2 adopts a distorted octahedral geometry as the carboxylate ligand N,O chelates an Sn atom and at the same time bridges a neighbouring Sn atom via the second O atom, with the remaining sites being occupied by the Cl and two C atoms; the O atoms are trans to each other. The result of the mu 2-bridging mode of L- is the formation of a supramolecular helical chain. Compound 4 adopts a skew-trapezoidal bipyramidal geometry with the organo groups lying over the plane of the two N,O-chelating carboxylate ligands and being directed over the weaker Sn?N bonds. The in vitro antimicrobial activities of 14 against a Gram-positive bacteria strain (Bacillus subtilis), a Gram-negative bacteria strain (Escherichia coli) and against Candida albicans were studied and compared with the antimicrobial activities of Ph2SnL2 and Me2SnL2, and with the antimicrobial standards gentamicin, tetracycline, ampicillin and penicillin. All organotin compounds displayed remarkable antibacterial activities that were comparable to those of the standard drugs, in particular against B. subtilis, where the activity was correlated with the number of Cl substituents. Copyright (C) 2012 John Wiley & Sons, Ltd.