Green synthesis and microcalorimetric study of a novel N-alkylation Schiff base and its bismuth(III) complex

A new N-alkylation Schiff base [N2,N6-bis(2-hydroxy-3-methoxybenzyl)pyridine-2,6-dicarboxamide] was synthesized from o-vanillin and pyridine-2,6-dicarboxamide by a solid-phase microwave green synthesis without catalyst and solvent. A new bismuth(III) complex was prepared by reaction of the ligand with BiCl3. The ligand and its bismuth(III) complex were characterized by elemental analysis, spectral techniques (1HNMR, MS, FT-IR and UV), chemical analysis, thermogravimetric analysis and molar conductance. The compositions of the ligand and its bismuth(III) complex were (C23H23N3O6) and Bi(C23H21N3O6)Cl. Moreover, the antibacterial activity of the ligand and its bismuth(III) complex against S. pombe was evaluated by bio-microcalorimetry at 32 °C. The quantitative relationship between some thermokinetic parameters (k, tG and I) with the concentration (c) of the ligand and its bismuth(III) complex was investigated. The half inhibition concentrations (IC50) of the ligand and its bismuth(III) complex were obtained as 4.63 × 10–3 mol dm−3 and 2.10 × 10–3 mol dm−3, respectively. The results showed that the antibacterial activity of bismuth(III) complex was stronger than that of the ligand. Further, the action target of bismuth(III) complex on bovine serum albumin (BSA) was studied by the molecular docking simulation method, and we found that bismuth(III) complex bounded at in the hydrophobic cavity of the substructure domain IIB of BSA.