Chemical stability of 1-substituted 2-aldimine- and 2-azobenzimidazoles under copper-promoted autoxidation

• Dimer and polymer Cu(II) complexes are formed in the absence of redox processes. • The Cu(I) complexation was accompanied with redox properties. • Cu(II) complexes with benzimidazole derivatives were synthesized. • The process depends on the solvent used and the nature of the organic ligand. Copper(I) and copper(II) complexation with N -donor heterocyclic ligands derived from benzimidazole has been studied. It has been found that starting from copper(II), dimeric [Cu 2 (μ–SO 4 ) 2 (DMF) 2 (H 2 O) 4 ] and polymeric [Cu(μ-SO 4 )(DMF)(H 2 O) 2 ] n copper(II) complexes are isolated that contain no organic ligands. Under redox conditions, when starting from copper(I), the instability of the 1-(1-benzylbenzimidazol-2-yl)- N -cyclohexylmethanimine ligand is found, which leads to the formation of copper(II) complexes with the modified benzimidazole derivative [Cu(2–O 2 CBz-R) 2 ] or [Cu 2 (2-OCH(OH)Bz-R) 2 Cl 2 ] (Bz is benzimidazole, R = CH 2 -C 6 H 5 ) depending on the solvent used. EPR spectroscopy revealed the presence of hyperfine interaction in compound [Cu(2-O 2 CBz-R) 2 ].