Stability constants, characterization, and Theoretical Modelling Studies of the Complexes of L- Ascorbic Acid with Transition Metal Ions

Abstract

Potentiometric measurements of L-ascorbic acid's ionization constant as a chelating drug and the stability constants of its Mn2+, Fe3+, Co2+, Cu2+, and Zn2+ metal complexes have been made in an ethanol-water (25% ethanol) and 1.0 molar NaCl medium. The complexes that were generated in solution had stoichiometry values of 1:1 and 2:1 (Asc: M), and the order of stability was Fe3+> Cu2+> Mn2+> Co2+> Zn2+. Different physico-chemical techniques were used to confirm the structures of the solid complexes where a satisfactory agreement between the proposed and theoretical formulae was found. The antibacterial activity toward some Gram positive, Gram negative and fungi was studied taking Ciprofloxacin and Ampicillin as standards. The outcomes show that the metal complexes have a marginally higher level of activity than ascorbic acid in its free form. The DMOL3 tool, designed for wide-scale density function theory (DFT), was used to calculate a few quantum chemical and energetic characteristics of the free drug and its metal complexes.