Solid State Photochemical Generation of Triplet Phenoxy-Phenoxy Radical Pairs.

摘要

Use of bis-aryloxalate neat solid samples to investigate ferromagnetic phenoxy-phenoxy geminate geminate coupling is described. The title compounds (described in Technical Report 16) form good crystals, which up cooling to 77K or below and irradiation with a Xenon arc lamp give ESR spectra indicating both monoradical signals and radical-radical triplet pair interactions. The size of the interaction may be qualitatively determined by the spectral extent of the triplet spectrum (80-120 Gauss), which at this preliminary stage suggests that the radicals are 6.0-7.0 angstroms apart. The spectra are shown and compared to spectra with similar features for solid state photolysis of diphenyl oxalate. Tert-butylated bis-aryloxalates show good radical pair stability, with triplet ESR signals surviving days at room temperature in some cases. Keywords: Solid state photochemistry, Organic photochemistry electron spin resonance spectroscopy of radical pairs, Organic magnetism. (JES)