Synthesis and spectral, antibacterial, molecular studies of biologically active organosilicon(IV) complexes

A series of new organosilicon(IV) complexes have general formulae R₃SiL and RSiLOEt with Schiff bases (R = Me and Ph). The Schiff bases (LH) have been derived from the condensation of (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone with semicarbazide, thiosemicarbazide, and phenylthiosemicarbazide, respectively. The compounds have been characterized by the elemental analysis, molar conductance, and spectral (UV, IR, ¹H, ¹³C, and ²⁹Si NMR) studies. These studies showed that the ligands coordinate with the silicon atom in a tridentate manner through phenolic oxygen, azomethine nitrogen and thiolic sulfur. Further applying experimental spectroscopic techniques, theoretical data calculated using density functional theory by B3LYP/6.31+g(d,p) has also been used for structural determination. The resulting complexes have been proposed to have trigonal bipyramidal and distorted octahedral geometries. Few representative Schiff base and their silicon complexes have been screened for their in vitro antibacterial activity against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) of selected compounds was determined. The screening results show that organosilicon(IV) complexes have better antibacterial activity than the free ligands.