Synthesis, spectroscopic characterization, biological screening, and theoretical studies of organotin(IV) complexes of semicarbazone and thiosemicarbazones derived from (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone

New organotin(IV) complexes of (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone thiosemicarbazone [(LH2)-H-1], (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone phenylthiosemicarbazone [(LH2)-H-2], and (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone semicarbazone [(LH2)-H-3] with formula [R2SnL] (where R = Bu and Me) have been synthesized. The ligands and their organotin(IV) complexes were characterized by elemental analyses, molar conductivity, molecular weight determination, electronic, Fourier-transform infrared, and H-1, C-13, and Sn-119 nuclear magnetic resonance spectral studies. The ligands act as tridentate and coordinate with organotin(IV) atom through the thiolate sulfur, azomethine nitrogen, and phenoxide oxygen atoms. The low molar conductance values in dimethylformamide indicate that the metal complexes are nonelectrolytes. Theoretical calculation is provided in support of the structures. The in vitro antimicrobial activities have been evaluated against Klebsiella sp., Bacillus cereus, Staphylococcus sp., Escherichia coli, Rhizopus, Aspergillus, Alternaria, and Penicillium. The screening results show that the organotin(IV) complexes have better antibacterial activities and have potential as drugs. Furthermore, it has been shown that dibutyltin(IV) derivative exhibits significantly better activity than the other organotin(IV) derivatives.