Mixed-Ligand Complex [Cu4(bpy)4(PO4)2(CO3)(H2O)2]: Synthesis, Crystal Structure, and Biological Properties

The reactions in the Cu(OAc)₂⋅H₂O–phytic acid–2,2'-bipyridine (bpy) system in aqueous methanol solutions resulted in the formation of a molecular different-ligand tetranuclear complex [(Cu₄(bpy)₄(PO₄)₂(CO₃)(H₂O)₂]⋅13H₂O (I), the structure of which was established from the X-ray diffraction data (CCDC no. 2262998). The molecule of complex I contains four non-equivalent Cu²⁺ cations, coordinating each two phosphate anions (\({\text{PO}}_{4}^{{3 - }}\) remaining after the transformation of the phytate ring), four neutral bpy molecules, two water molecules, and one carbonate anion (\({\text{CO}}_{3}^{{2 - }}\)). The presence of a large number of solvate water molecules in the outer coordination sphere gives rise to a hydrogen-bonded framework involved in stabilization of the crystal packing. Study of the antimycobacterial activity of I against non-pathogenic Mycolicibacterium smegmatis strain revealed high biological efficacy.