INVESTIGATION AND OPTIMIZATION OF COMPLEXATION OF COBALT IONS WITH DIHYDROQUERCETIN IN AQUEOUS SOLUTIONS

We continue to study the reactions of complexation of biogenic metal ions with flavonoid dihydroquercetin (DHQ). The interaction of Co2+ ions with DHQ in aqueous solutions has been studied. It is established that complexes with different stoichiometry are formed at different pH values of the solution. Changing the pH of the solution from 6.0 to 7.0 leads to the formation of compounds 1–3 with a metal: flavonoid ligand (Met: L) ratio from 1: 2 at pH 6.0 (1) via 2: 3 at pH 6.4 -6.7 (2) to 1: 1 at pH 6.8-7.0 (3). Using the method of thermogravimetry with elemental analysis data, the most probable composition of compounds was established with the determination of the amount of bound water: [CoL2(H2O)4] for 1, [Co2L3(OH)(H2O)4] for 2 and [CoL(OH)(H2O)2] for 3. The conditions for the complexation of Co2+ ions with dihydroquercetin in aqueous solutions to form compound 2, optimized for the yield of the product, are proposed. pH of the solution is 6.7, the reaction time is 15 minutes, the temperature of the reaction solution is 90 °C, molar ratio of the initial reagents DHQ:Co2+ is 1: 1.5, initial concentrations are 0,020 M DHQ and 0,030 M Co2+, the source of Co2+ is CoSO4∙7H2O. The yield of the product is 81.8 %.