Complexation of Copper(II) and Cobalt(III) with (5-ethoxy-1-methylbenzimidazol-2-yl)-(4-methoxyphenyl)Methanol: Synthesis, Structure, and Biological Properties

Abstract

A new heterocyclic compound belonging to the class of secondary alcohols, (5-ethoxy-1-methylbenzimidazol-2-yl)(4-methoxyphenyl)methanol (1), and its copper(II) (2a, 2b) and cobalt(III) (3) complexes are synthesized. The structures of these compounds are established by elemental analysis, IR and NMR spectroscopy, and single crystal X-ray diffraction. Depending on the crystallization conditions, two crystal modifications are formed from copper(II) acetate and ligand 1: 2a (tetranuclear cubane-type Cu₄O₄ cluster, space group P2₁2₁2) and 2b (chain structure with a Cu₂O₂ core and acetate bridges, space group C2/c). In both cases, the ligand is coordinated in a bidentate mode through the nitrogen atom of the benzimidazole ring and the oxygen atom of the deprotonated alcohol group. The acetate groups act as intra-core bridges in 2a and perform a dual function - bridging and terminal - in 2b. Complex 3 is mononuclear octahedral Co(III) compound (space group \(R\bar{3}\)) with disordered hydroxyl protons. Complex 2b exhibits strong anticoccidial activity exceeding that of the parent alcohol and the reference drug toltrazuril. It is shown that ligand 1 has high structural flexibility for the targeted tuning of the coordination architecture of its complexes.