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New tin(II) complexes of general stoichiometry [Sn(L)2] with bidentate ligand, derived from amino acids with isatin, 5-chloroisatin have been synthesized. It is characterized by elemental analyses, molar conductance measurements, and molecular weight determinations. Bonding of these complexes is discussed in terms of their UV-visible, infrared, and nuclear magnetic resonance (1H, 13C, and 119Sn NMR) spectroscopic studies. The ligands act as bidentate towards metal ions, via the azomethine nitrogen and deprotonated oxygen of the respective ligands. The bond length, bond angles, highest occupied molecular orbital, lowest unoccupied molecular orbital, chemical hardness, global softness, and the lowest energy model structure of the complexes have been determined by density functional theory (DFT) calculations at B3LYP/LanL2DZ level. A few representative ligands and their tin complexes have been screened for their antibacterial activities and found to be active in this respect.

We report on the development of a novel green synthetic protocol for the series of pyrano-pyrazole derivatives (5an) in a one-pot multi-component method using CaO nanoparticles as the heterogeneous catalyst. The CaO nanoparticles were synthesized by a greener route using an economic and efficient alternative i.e. papaya leaf extract and exhibited excellent catalytic activity, and this plant-mediated synthesis of CaO nanoparticles is a very promising area of research. CaO nanoparticles can be efficiently used in the synthesis of pyrano-pyrazoles and this catalytic approach can deliver the appropriate products in a rapid reaction time with a high yield (85-91%). The current protocol has various advantages, including a short reaction time, a high percent yield, a clean reaction, a simple separation technique, and a recoverable catalyst that retains its catalytic activity when utilized in subsequent reactions. Characterization of synthesized pyrano-pyrazole derivatives is done by IR, 1H and 13C NMR spectral data as well as HOMO-LUMO calculations. [ABSTRACT FROM AUTHOR]

New lead(II) complexes have been synthesized with Schiff bases derived from 4-methoxybenzaldehyde and amino acids (tryptophan, phenylalanine, valine, isoleucine, methionine, histidine, alanine, cysteine, serine and aspartic acid). These ligands act as monobasic bidentate species and coordinate to the lead atom through the azomethine nitrogen and carboxylate oxygen atom. The synthesized complexes have been characterized by conductance measurements, elemental analysis and molecular weight determinations. The mode of bonding of the ligands and lead(II) complexes have been confirmed on the basis of infrared, UV-visible, and 1H, and 13C NMR spectroscopic studies, and probable structures have been assigned to these complexes. The optimized structural parameters such as bond length, bond angles, HOMO orbital, LUMO orbital, dipole movement, electronegativity, global softeness, electrophilicity index and mulliken atomic charges were calculated by the methods based B3LYP on the density functional theory (DFT). The ligands and their corresponding lead(II) complexes have also been screened for antibacterial activities. [ABSTRACT FROM AUTHOR]

A new series of metal complexes [M(L)2] (where M = Sn(II), Pb(II), and HL = semicarbazone, thiosemicarbazone or phenylthiosemicarbazone) have been prepared and characterized by elemental analysis, conductance measurements, molecular weight determinations, UV–visible, infrared, and nuclear magnetic resonance (1H-,13C-, and119Sn-NMR) spectral studies. Elemental analysis of the metal complexes suggested 1 : 2 (metal–ligand) stoichiometry. Infrared spectra of the complexes agree with coordination to the metal through the nitrogen of the azomethine (>C=N−) and the oxygen/sulfur of the ketonic/thiolic group. Electronic spectra suggest a distorted tetrahedral geometry for all Schiff base complexes. The bond lengths, bond angles, highest occupied molecular orbital, lowest unoccupied molecular orbital, Mulliken atomic charges, and the lowest energy model structure of the complexes have been determined with DFT calculations. Representative Schiff base and its metal chelates have been screened for theirin vitroantibacterial activity against four bacteria, Gram-positive (Bacillus cereus,Staphylococcus aureus) and Gram-negative (Escherichia coli,Klebsiella pneumoniae) and four strains of fungus (Penicillium chrysogenum,Aspergillus niger,Rhizopus nigricans, andAlternaria alternata). The metal chelates possess higher antimicrobial activity than the free ligands. [ABSTRACT FROM PUBLISHER]

The present work stems from our interest in the synthesis, characterization, and antibacterial evaluation of organosilicon(IV) complexes of a class of amino-acid-based Schiff base which have been prepared by the interaction of ethoxytrimethylsilane with the Schiff bases (NOH) in 1 : 1molar ratio. These complexes have been characterized by elemental analysis, molar conductance, and spectroscopic studies including electronic IR and NMR (¹H, 13C, and 29Si) spectroscopy. The analytical and spectral data suggest trigonal bipyramidal geometry around the silicon atom in the resulting complexes. The ligands and their organosilicon complexes have also been evaluated for in vitro antimicrobial activity against bacteria (Bacillus cereus, Nocardia spp., E. aerogenes, Escherichia coli, Klebsiella spp., and Staphylococcus spp.). The complexes were found to be more potent as compared to the ligands. [ABSTRACT FROM AUTHOR]