Synthesis, spectroscopic characterization and in vitro antimicrobial activity of diorganotin(IV) dichloride adducts with [1,2,4]triazolo-[1,5-a]pyrimidine and 5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidine

The heterocyclic ligands [1,2,4]triazolo-[1,5-a]pyrimidine (tp) and 5,7-dimethyl-[1,2,4]triazolo-[1,5-a]pyrimidine (dmtp), react with diorganotin dichlorides giving the addition compounds Me2SnCl2(tp)(2), Et2SnCl2(tp)(2), Me2SnCl2(dmtp)(2), Et2SnCl2(dmtp)(2), Bu2SnCl2(dmtp), Ph2SnCl2(dmtp). The organotin:ligand stoichiometry goes from 1:2 to 1:1 by increasing the steric hindrance of the organic groups bound to tin. The compounds have been characterized by means of infrared, Sn-119 Mossbauer and H-1 AND C-13 NMR spectroscopy. The ligands presumably coordinate to tin classically through the nitrogen atom at the position 3. The 1:1 complexes adopt trigonal bipyramidal structures, with the organic groups on the equatorial plane and the ligand in the apical position. All-trails octahedral structures are inferred for the 1:2 complexes, except for Et2SnCl2(tp)(2), characterized by a skew-trapezoidal structure. Sn-119 Mossbauer measurements, at room temperature, in concomitance with DFT calculations, performed on isomeric structures of R2SnCl2(tp)(2) (R = Me, Et), allowed us to conclude that the all-trans octahedral coordination induces self-assembly in the solid state, possibly accomplished through pi-pi stacking interactions among the planar ligands coordinated to the organotin(IV) compound, while the skew-trapezoidal structure attributed to Et2SnCl2(tp)(2), induces the formation of monomeric adducts in the solid state. In vitro antimicrobial tests showed that [n-Bu2SnCl2(dmtp)] has interesting properties as anti Gram-positive and antibiofilm agent. (c) 2005 Elsevier B.V. All rights reserved.