Synthesis, spectral, DFT, and antimicrobial studies of tin(II) and lead(II) complexes with semicarbazone and thiosemicarbazones derived from (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone.

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]