Photoinduced Electron Transfer in 9-Substituted 10-Methylacridinium Ions

Takeshi Tsudaka; Hiroaki Kotani; Kei Ohkubo; Tatsuo Nakagawa; Nikolai V Tkachenko; Helge Lemmetyinen; Shunichi Fukuzumi

doi:10.1002/chem.201604527

Photoinduced Electron Transfer in 9-Substituted 10-Methylacridinium Ions

Chemistry. 2017 Jan 26;23(6):1306-1317. doi: 10.1002/chem.201604527. Epub 2016 Dec 14.

Authors

Takeshi Tsudaka¹, Hiroaki Kotani², Kei Ohkubo^{1

3

4}, Tatsuo Nakagawa⁵, Nikolai V Tkachenko⁶, Helge Lemmetyinen⁶, Shunichi Fukuzumi^{3

7}

Affiliations

¹ Department of Material and Life Science Graduate School of Engineering, Osaka University and SENTAN, Japan Science and Technology Agency (JST), Suita, Osaka, 565-0871, Japan.
² Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, 305-8571, Japan.
³ Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 120-750, Korea.
⁴ Division of Innovative Research for Drug Design, Institute of Academic Initiatives, Osaka University, Suita, Osaka, 565-0871, Japan.
⁵ Unisoku Co. Ltd, SENTAN, Japan Science and Technology Agency (JST), Hirakata, Osaka, 573-0131, Japan.
⁶ Institute of Materials Chemistry, Tampere University of Technology, P.O. Box 541, 33101, Tampere, Finland.
⁷ Faculty of Science and Technology, Meijo University, SENTAN, Japan Science and Technology Agency (JST), Nagoya, Aichi, 468-8502, Japan.

PMID: 27813180
DOI: 10.1002/chem.201604527

Abstract

A series of 9-substituted 10-methylacridinium ions (Acr⁺ -R) in which an electron-donor moiety (R) is directly linked with an electron-acceptor moiety (Acr⁺ ) at the 9-position was synthesized, and the photodynamics was fully investigated to determine the rate constants of photoinduced electron transfer (ET) and back electron transfer. The driving forces of photoinduced electron transfer and back electron transfer were determined by means of electrochemical and photophysical measurements. The dependence of the ET rate constants on driving force was well analyzed in the light of the Marcus theory of ET. The quantum yields of formation of the triplet ET states vary significantly, depending on the interaction between the donor (R) and acceptor (Acr⁺ ) moieties. Among the Acr⁺ -R examined, the 9-mesityl-10-methylacridinium ion (Acr⁺ -Mes) exhibits the best performance in terms of the lifetime of the triplet ET state and the quantum yield. Photoexcitation of Acr⁺ -Mes results in formation of the triplet ET state [³ (Acr^. -Mes^.+ )], which has a long lifetime, a high energy (2.37 eV), and a high quantum yield (>75 %) in acetonitrile. The triplet ET state exhibits both the oxidizing and reducing activity of the Mes^.+ and Acr^. moieties, respectively.

Keywords: donor-acceptor systems; electron transfer; photochemistry; redox chemistry; time-resolved spectroscopy.