Unprecedented iminobenzosemiquinone and iminobenzoquinone coordinated mononuclear Cu(ii) complex formation under air

Abstract

Two non-innocent 2-anilino-4,6-di-tert-butylphenol units were connected through an -ortho bridging S atom and provided the ligand H₄L^S(AP/AP). The ligand reacted with CuCl₂·2H₂O in the presence of Et₃N under air and generated a mononuclear Cu(II) complex (1, [CuL^S(IBQ/ISQ)Cl]⁰). A single crystal X-ray diffraction analysis confirmed that in the complex one of the two 2-anilido-4,6-di-tert-butylphenol arms was present in its one-electron oxidized iminobenzosemiquinone form, while the other was in its two-electron oxidized iminobenzoquinone form. The monoradical-containing Cu(II) complex was diamagnetic in nature owing to a strong antiferromagnetic coupling between the single electron containing d_x²–y² magnetic orbital of Cu(II) and the radical-centered unpaired electron.