ESR and optical properties of copper atoms in γ-irradiated organic solutions at 77 K

EtOH and MTHF solutions containing Cu+ ions are gamma -irradiated at 77 K. ESR spectra are attributed, for the first time, to Cu-0 that is produced radiation-chemically by reducing Cut ions in the solutions at 77 K. A large delocalization of the unpaired spin density of Cu-0 onto ligands is deduced. No evidence for formation of the dimer cation of Cu-0 has been obtained. This is contrary to the case of Ag-0 produced in the solutions containing Ag+ ions. The NUV absorption spectrum of Cu-0 is decomposed into five Gaussian bands that are attributed to two types of exciplexes formed between excited Cu-0 and ligands: one associates with Cu+ ions as well as solvent molecules, the other consists mainly of solvent molecules. The exciplexes are supposed to be transferred to relaxed states followed by two emission bands, one of which is common to both solvents and the other is characteristic of the solvents. The absorption band at 255 nm is ascribed to a photoionization spectrum of Cu-0.