ESR and Optical Properties of Copper Atoms in γ-Irradiated Organic Solutions at 77 K

Abstract

EtOH and MTHF solutions containing Cu + ions are γ-irradiated at 77 K. ESR spectra are attributed, for the first time, to Cu 0 that is produced radiation-chemically by reducing Cu + 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 .

Effects of UV Irradiation on ESR and Optical Properties of Cu(II) Ions in Organic Solid Solutions Containing CuCl at 77 K

“…We will mention this later in detail. The ESR spectra obtained after irradiation in the present study subsequent to uv irradiation were the same as those reported previously [10]. As shown in spectra (c) in Figs.…”

“…We also proved experimentally that an admixture of the wave function of the Cu 0 atom in its ground state 2S 1/2 : 3d 10 4s 1 into 3d x 2 y 2 is expected to occur to some extent. The five nuv absorption bands represented as bands from C 1 to C 5 were observed after irradiation in the organic solid solutions at 77K [10]. We attributed them to the two types of exciplexes formed between excited Cu 0 atoms and the ligands: one associates with Cu + ions as well as solvent molecules, the other consists mainly of solvent molecules.…”

“…The color of solutions was faded away at liquid nitrogen temperature, except for the MTHF solution of 10 -1 M, which colored slightly yellow. The procedures of sample preparation were the same as in our previous studies [10]. The effect of evacuation of the samples by freeze-pump-thaw method as well as sealing the sample tubes was not observed on the ESR spectral characteristics.…”

“…The effect of evacuation of the samples by freeze-pump-thaw method as well as sealing the sample tubes was not observed on the ESR spectral characteristics. In order to investigate the ESR and optical properties for the samples of the solid solutions containing Cu(I) and Cu(II) under the same conditions, we have used the same CuCl systems as in the previous study [10]: EtOH as the polar solvent and MTHF as less polar solvent were used to investigate dependence of polarity on the spectral characteristics.…”

“…As a fundamental research to elucidate the function and effects of metal ions and/or atoms in biological systems, we have been investigating the ESR and optical properties of 1B metal atoms produced radiation-chemically by reducing their mono cations in solid solutions [4][5][6][7][8][9][10][11][12]. In the series of our previous studies, formation of metal atoms, Cu 0 , Ag 0 and Au 0 in irradiated solid solutions containing their mono cations were evidenced by ESR spectra that exhibited duplicate quartets [10], duplicate doublets [8] and quartet [12], respectively. The values of the hyperfine splitting, a and the gyromagnetic ratio for the electron shell, g J were evaluated from the Breit-Rabi equations that were applied for the case of isotropic forces of interaction between trapped atoms and ligands.…”