The Role of Organic Glasses in cis/trans Photoisomerization at Low Temperatures

Into the looking glass! Low temperature photoisomerization studies on some arenes have been studied in different organic glasses. The results are consistent with a possible softening of the glass and offer an explanation for the mechanism of photoisomerization in a confined medium. Low temperature photoisomerization of stilbene and 1,4‐diphenyl‐1,3‐butadiene derivatives was found to vary depending on the organic glass employed in such studies. Examination of the combined results showed that the variation was more likely to arise from the rigidity of the organic glass at the temperature of irradiation rather than the composition of the organic glass; that is, the observed results are consistent with the possible softening of the glass that surrounds the excited substrate in the same manner as detected in the photolysis of ethyl iodide reported by Porter and co‐workers. These observations successfully account for the apparent “disagreement” of reports from the Hawaii and the Florida State groups on the mechanism of photoisomerization in low temperature glasses. Into the looking glass! Low temperature photoisomerization studies on some arenes have been studied in different organic glasses. The results are consistent with a possible softening of the glass and offer an explanation for the mechanism of photoisomerization in a confined medium.