4, 4'-ジヒドロキシビフェニルの光酸化により生じるフリーラジカル

Abstract

Photolysis of 4, 4'-dihydroxybiphenyl (BPH2) gave a cation radical (BPH2+·), 4-hydroxy-4'-biphenoxyradical (BPH·) and the conjugate base (BP-·) of BPH· in EPA at 77K. The absorption spectra of the radicals were measured in a wide wavelength region, 350-1000 nm, and the first electronic absorption bands of BPH2+·, BPH· and BP-·. are at 620, 649 and 787 nm, respectively. Irradiation of BPH2 in poly (vinyl alcohol) film at 103 K afforded the mixture of BPH2+· and BP-· BPH2 changed to BP-· predominantly with increasing temperature. The first bands of BPH2+.(640nm) and BP-· (823nm) are polarized along the longer molecular axes. The first transition of BPH2+· corresponds to the transitson from the half-occupied orbital to the lowest vacant orbital, and is interpreted as an intramolecular charge transfer one from the two oxygen atoms to the biphenyl skeleton. The first transition of BP-· corresponds to the transition from the highest occupied orbital to the half-occupied one.