Sulfonamide-derived hydrazone compounds and their Pd (II) complexes: Synthesis, spectroscopic characterization, X-ray structure determination, in vitro antibacterial activity and computational studies

A new sulfonamide-derived prophane sulfonyl hydrazone compounds: 2-hydroxy- acetophenoneprophanesulfonylhydrazone (afpsh), 5-Cl-2-hydroxyacetophenoneprophane sulfonylhydrazone (5-Clafpsh), 3,5-di-tert-butyl-2-hydroxybenzaldehydeprophanesulfonyl hydrazone (3,5tbsalpsh) and their Pd(II) complexes were synthesized. The characterization of all compounds was characterized by 1H NMR, 13C NMR, FT-IR, Mass spectral data, elemental analysis and magnetic susceptibility measurements. The crystal structure of afpsh was determined by single crystal X-ray diffraction methods. 1H and 13C shielding tensors of afpsh were calculated with GIAO/DFT/B3LYP/6–311++G(d,p) methods in DMSO. Molecular electrostatic potential surface and frontier orbital analysis were also carried out. HOMO-LUMO energy gap was calculated which allowed the calculation of relative reactivity descriptors like chemical hardness, chemical inertness, chemical potential, nucleophilicity and electrophilicity index of all compounds. It has been observed that the calculated band gaps for Pd (II) complexes are much smaller than ligands. The microbiological effect of ligands and Pd(II) complexes were tested against six human pathogenic bacteria (three Gram-positive and three Gram-negative strains) by using microdilution (as MICs) and disc diffusion (as mm zone) methods. It was found that all compounds, in particular Pd (II) complexes, were more active than sulfonyl hydrazones.