Photochromic Reaction by Red Light via Triplet Fusion Upconversion
J. Am. Chem. Soc., 2019,Just Accepted.
Ayako Tokunagaa, Lucas Martinez Uriarteb, Katsuya Mutoha, Eduard Fronc, Johan Hofkensc, Michel Sliwab and Jiro Abea
a Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo ku, Sagamihara, Kanagawa 252-5258, Japan
b Univ. Lille, CNRS, UMR 8516, LASIR, Laboratoire de Spectrochimie Infrarouge et Raman, F59 000 Lille, France
c Leuven Chem&Tech: Molecular Imaging and Photonics (MIP), KU Leuven, Celestijnenlaan 200F, P.O. Box 2404, 3001 Leuven, Belgium
Red or near infrared (NIR) light responsive molecules have received much attention for biological and material applications because potentially harmful UV light for materials and cells is not required for the photochemical reactions. Although some molecular designs for photochromic molecules to increase the photosensitivity to red or NIR light have been reported, the strategies are limited to the extension of π-conjugation length and the utilization of charge transfer transition or energy and electron transfers. Triplet fusion is an attractive tool to cause chemical reactions by converting low energy excitation light to high energy upconversion light. However, the efficient use of the high energy of upconversion light is difficult because almost all reported triplet fusion systems rely on re-absorption of upconversion light. Here, we demonstrated the red-light driven photochromism via the triplet fusion of a phenoxyl-imidazolyl radical complex, Pery-RPIC, that has a covalently bonded perylene as an annihilator unit. The femtosecond time-resolved absorption and fluorescence spectroscopy revealed that this photochromic reaction proceeds by the highly efficient singlet energy transfer from the annihilator unit to the photochromic unit. This strategy can be applied not only to the development of visible and NIR light responsive photochromic system but also to various photochemical reactions.