COORDINATION BEHAVIOR OF TRANSITION METAL CATIONS WITH SUBSTITUTED SALICYLIC ACIDS AND COMPUTATIONAL STUDIES OF BIOLOGICAL POTENTIAL

Abstract

The complexation behavior of several salicylic acid derivatives with Fe³⁺, Co²⁺, Cu²⁺, and Zn²⁺ ions was examined using spectrophotometric titration. Under optimized conditions, the resulting metal complexes were isolated and their spectral characteristics were analyzed. Spectroscopic evidence indicates that these complexes form through bidentate coordination, involving the ionized hydroxyl group and the carboxylic oxygen atom. These observations align with FTIR data and previously reported X-ray crystallographic findings for related metal complexes of α-hydroxy carboxylic acids.

In silico analyses were also conducted to assess the potential biological activities of the synthesized complexes compared to their free ligands. The computational results suggest that the most likely biological effects involve inhibition of the multiprotein complex within the respiratory electron transport chain and potential antitumor properties, both of which show slight modifications upon complexation. Furthermore, predictive modeling indicates that 2,3-dihydroxybenzoic acid, 3-methoxysalicylic acid, and their divalent metal complexes are likely to be absorbed through the gastrointestinal tract, whereas 3,5-dinitrosalicylic acid (3,5-DNSA) and Fe³⁺ complexes exhibit poor bioavailability.