Antiproliferative Potential of Cobalt(II) Phenanthroline Complexes with Pyridonates

The reaction of CoCl₂ · 6H₂O with 6-chloro-2-hydroxypyridine (Hchp) and 1,10-phenanthroline (phen) afforded the complex [Co(chp)₂(phen)] (<b>1</b>). Although this complex has been previously reported, it was obtained in this work under mild conditions (in acetonitrile at room temperature) and characterized for the first time by single-crystal X-ray diffraction. The use of Co(F₃CCOO)₂ · 4H₂O under similar conditions yielded a new trinuclear molecular complex [Co₃(chp)₂(F₃CCOO)₄(phen)₂] (<b>2</b>). According to X-ray diffraction data, the cobalt(II) ions in complexes <b>1</b> and <b>2</b> are located in an octahedral environment (coordination number CN_Co = 6). As an ambidentate ligand, Hchp exhibits different types of coordination modes in the resulting complexes <b>1</b> and <b>2</b>. Additional stabilization of molecules in the crystal is achieved by π-π stacking between aromatic systems of coordinated phen ligands. The cytotoxic activity of <b>1</b> and [CoCl₂(phen)₂] · 1.5MeCN (<b>3</b>) against a panel of human cancer cell lines (SKBR3, HCT116, A549) and normal dermal fibroblasts (HDF) was evaluated using the MTT assay. Complex <b>3</b> demonstrated cytotoxic activity against the HCT116 cell line comparable to that of cisplatin, indicating its potential as a promising antitumor agent.