Synthesis, crystallographic and spectroscopic characterization, and theoretical elucidation of an elusive aminyl radical containing a Cu-aminyl-iminosemiquinone complex

An elusive aminyl radical and an iminosemiquinone radical-coordinated square pyramidal Cu( ii ) complex ( 1 ) have been isolated by the reaction between the noninnocent ligand H 4 L Py (AP) and Cu(ClO 4 ) 2 ·6H 2 O in the presence of Et 3 N and air as the sole oxidant. The geometry and electronic structure of the complex were concluded by X-ray crystallography, magnetic and EPR measurements, and density functional theory (DFT) calculations. This work reports the first crystallographic example of the two different types of radicals co-existing in a stable complex. A thermodynamically unstable amine radical and an iminosemiquinone radical-coordinated square pyramidal Cu( ii ) complex are isolated and established by X-ray crystallography, magnetic and EPR measurements, and DFT calculations.