Study on a nonclassical radical cation using time-resolved absorption spectroscopy and DFT calculations

Abstract

We previously reported the photoinduced electron-transfer (PET) degenerate methylenecyclopropane (MCP) rearrangement of diarylmethylenecyclopropane (1). The reaction proceeds via two different types of intermediates, a trimethylenemethane (TMM) radical cation (2 radical cation), and TMM biradical (2-biradical). The MCP rearrangement of 1 was also triggered by g-ray irradiation in a low temperature glassy matrix. The most characteristic feature is that the intense thermoluminescence (TL) was observed on the annealing of the sample matrix. Spectroscopic studies and energetic analyses suggest that the TL is originated from the excited state of TMM, (2-biradical)*, which is generated by electron-transfer (ET) reaction of 1 followed by bond cleavage and charge recombination. A potential application of the ET reaction of 1 toward organic electroluminescence will be also discussed.