Interaction of pyridoxal-derived hydrazones with anions and Co<sup>2+</sup>, Co<sup>3+</sup>, Ni<sup>2+</sup>, Zn<sup>2+</sup> cations
G. A. Gamov, Maksim N. Zavalishin, Maria V. Petrova, Anisya Khokhlova, A. V. Gashnikova, A. N. Kiselev, В. А. Шарнин
Abstract
Present paper reports on the interactions between four hydrazones derived from pyridoxal and hydrazides of 2-furoic, thiophene-2-carboxylic, pyrazinoic and pyridine-3-carboxylic acids and 10 different anions (F−, Cl−, I−, PO43-, HPO42-, H2PO43-, NO3−, SO32-, SO42-, CH3COO−) and three cations (Co2+, Ni2+, Zn2+). Hydrazones are sensitive towards anion presence in non-buffered DMSO only, thus, indicating that the proton transfer from ligand towards anion is responsible for the changes in colour, UV-Vis and fluorescent spectra. Buffered solutions of ligand mixture with any anion are indistinguishable from free hydrazone. The addition of d-metal ions to pyridoxal-derived hydrazones dissolved in buffered DMSO changes the solution colour, UV-Vis and fluorescent spectra. Conditional rate constants of Co2+ oxidation, as well as the apparent stability constants of Co2+, Co3+ complexes with Schiff bases, were determined from kinetic experiments, while Ni2+, Zn2+ complexes stability constants were calculated from UV-Vis and fluorimetry titration data.