π-Topology and ultrafast excited-state dynamics of remarkably photochemically stabilized pentacene derivatives with radical substituents
Nishiki Minami, Kohei Yoshida, Keijiro Maeguchi, Ken Kato, Akihiro Shimizu, Genta Kashima, Masazumi Fujiwara, Chiasa Uragami, Hideki Hashimoto, Yoshio Teki
Abstract
Pentacene derivatives with both π-radical- and TIPS-substituents (1m and 1p) were synthesized and their photochemical properties and excited-state dynamics were evaluated. The pentacene-radical-linked systems 1m (1p) showed a remarkable improvement in photochemical stability, which was 187 (139) times higher than that of 6,13-bis(triisopropylsilylethynyl)pentacene. Transient absorption spectroscopy showed that this remarkable photostabilization is due to the ultrafast intersystem crossing induced by effective π-conjugation between the radical substituent and pentacene moiety. The relationship between π-topology and the photochemical stability is also discussed based on the excited-state dynamics.