New metal complexes of azo ligand based on a monoterpene core: synthesis, structural characterization, antioxidants, and DNA-cleavage activity

Abstract

New mononuclear complexes of Cr(III), Fe(III), Zn(II), Mo(IV), and Cd(II) have been designed and synthesized, utilizing a tridentate azo ligand, 1-(5-allyl-2-hydroxy-3-methoxyphenyl)diazenyl)anthraquinone (H-L), derived from amino anthraquinone and the phenolic monoterpene (eugenol), known for its diverse pharmacological characteristics. The free ligand and its metal chelates were characterized by various complementary spectroscopic, spectrometric, thermal, magnetic, and analytical techniques. According to the molar conductivity data, all complexes except the Mo(IV) complex behave as neutral species. The in vitro antioxidant activity, as estimated by the DPPH assay, showed concentration-dependent radical-scavenging activity for the ligand and its complexes, with the Cr(III) complex demonstrating potency comparable to that of the standard (Trolox). DNA-cleavage studies revealed pronounced activity for the Cr(III), Fe(III), Zn(II), and Mo(IV) complexes in the absence of external redox agents. In contrast, the Cd(II) complex showed no apparent activity. These results reveal that anthraquinone-natural monoterpene (eugenol)-based azo ligand serves as an effective scaffold for bioactive coordination compounds that function as DNA-targeting and antioxidant agents, thereby suggesting their potential as promising candidates for future biological applications. KEY WORDS: Azo ligand, Antioxidant, DNA cleavage, Metal complexes, Monoterpene (Eugenol) Bull. Chem. Soc. Ethiop. 2026, 40(12), 2655-2669.                                                                         DOI: https://dx.doi.org/10.4314/bcse.v40i12.11