Synthèse, caractérisation et évaluation biologique des composés hétérocycliques

Abstract

This work focuses on the synthesis and characterization of new Schiff base ligands of the hydrazone and azine type, derived from furanic and thiophenic heterocyclic precursors, together with the preparation of a cobalt(II) complex. In the first stage, furoin was obtained through a cyanide-catalyzed furoin condensation. This α-hydroxy ketone was subsequently reacted with hydrazine hydrate, alongside furfural and thiophene-2-carboxaldehyde, to afford a series of six ligands: three hydrazones (L1, L2, L3), one symmetric azine (L4), and two unsymmetrical azines (L5, L6). The complex [Co(L2)₂Cl₂] was prepared by reacting ligand L2 with hydrated cobalt(II) chloride in a 2:1 molar ratio.

All compounds were characterized by infrared (IR) and UV-Visible spectroscopy, and selected ligands along with the complex were further studied by cyclic voltammetry. IR spectra confirmed the formation of the C=N bond characteristic of hydrazone and azine functions, while the electrochemical study revealed an irreversible redox behavior for the ligands and a quasi-reversible one for the cobalt(II) complex.

The antioxidant activity of compounds L2, L4, L5, and [Co(L2)₂Cl₂] was assessed using both DPPH and ABTS radical scavenging assays. Ligand L2 proved to be the most active in the ABTS test (IC₅₀ = 23.70 µM), likely acting through an electron transfer mechanism, whereas L4 displayed a mixed and dose-dependent antioxidant profile in both assays. Although moderate compared to reference standards, these results are encouraging and open avenues for further biological investigations