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A series of new organosilicon(IV) complexes have general formulae R 3 SiL 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, 1 H, 13 C, and 29 Si 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.

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A new series of organotin(IV) and organosilicon(IV) complexes were synthesized using the Schiff base ligands [2-((3,4-dimethoxybenzylidene)amino)-3-(1H-indol-3-yl)propanoic acid (L1H) and 2-((3,4-dimethoxybenzylidene)amino)-3-methylbutanoic acid (L2H)]. The synthesized compounds were characterized by IR, NMR (1H and13C), elemental analysis and theoretical studies. The molar conductivity values of the complexes in DMF implied the presence of non-electrolyte species. Spectral data showed that in these complexes the metal atoms are coordinated with the Schiff base ligand acts as a bidentate ON moiety, coordinating to the metal through its carboxylate oxygen and imine nitrogen. The IR spectra of the complexes showed large differences between νasy(COO) and νsy(COO), Δν (νasy(COO)–νsy(COO)) of 260-276 cm–1, indicating monodentate nature of the carboxylate group. Furthermore, the density functional theory (DFT) calculations were executed at the B3LYP/6-31G(d,p)/ LanL2DZ basis set of theory for the optimized geometry of Schiff base complexes. The structural parameters, bond length, bond angles, chemical potential, electronegativity, hardness, softness, global electrophilicity index have been studied theoretically by density functional theory (DFT) to support the experimental results.