Synthesis and microcalorimetric determination of the bioactivities of a new Schiff base and its bismuth(III) complex derived from o-vanillin and 2,6-pyridinediamine

In this work, a new Schiff base [N,N′-bis(2-hydroxy-3-methoxyphenylmethylidene)-2,6-pyridinediamine, C21H19N3O4] and its bismuth(III) complex [Bi(C21H17N3O4)]Cl·2H2O were synthesized with o-vanillin and 2,6-pyridinediamine in ethanol and THF solvent, respectively. The compositions and structures of the two synthetic compounds were characterized by elemental analysis, chemical analysis, spectrum analysis (including MS, FT-IR, NMR, and UV–Vis), and thermogravimetric analysis. The thermogenic curves for the growth metabolism of Helicobacter pylori (H. pylori) and Schizosaccharomyces pombe (S. pombe) treated by different concentrations of the two synthetic compounds were determined by isothermal heat conduction microcalorimetry at 37.00 and 32.00 °C, respectively. Based on the thermogenic curves, some important thermokinetic parameters including the microbial growth rate constant (k), inhibition ratio (I), and half inhibition concentration (IC50) were calculated. The obtained results revealed that the Schiff base stimulated the growth of H. pylori, while the complex inhibited its growth. By contrast, both the Schiff base and the complex inhibited the growth of S. pombe, but the inhibitory effect of the complex was stronger than that of the Schiff base.