title: Aggregation-induced photon upconversion through control of the triplet energy landscapes of the solution and solid states.
abstract: Aggregation-induced photon upconversion (iPUC) based on control of the triplet energy landscape is demonstrated for the first time. When a triplet state of a cyano-substituted 1,4-distyrylbenzene derivative is sensitized in solution, no upconverted emission based on triplet-triplet annihilation (TTA) was observed. In stark contrast, crystalline solids obtained by drying the solution revealed clear upconverted emission. Theoretical studies unveiled an underlying switching mechanism: the excited triplets in solution immediately decay back to the ground state through conformational twisting around a CC bond and photoisomerization, whereas this deactivation path is effectively inhibited in the solid state. The finding of iPUC phenomena highlights the importance of controlling excited energy landscapes in condensed molecular systems.
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan).
authors.forename: Pengfei
authors.initials: P
authors.lastname: Duan
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan). yanai@mail.cstm.kyushu-u.ac.jp.|JST-PRESTO, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan). yanai@mail.cstm.kyushu-u.ac.jp.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Yanai
authors.affiliation: JST-PRESTO, Honcho 4-1-8, Kawaguchi, Saitama 332-0012 (Japan).|Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8585 (Japan).|Department of Functional Molecular Science, School of Physical Sciences, The Graduate University for Advanced Studies, Okazaki, Aichi 444-8585 (Japan).
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kurashige
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan). n-kimi@mail.cstm.kyushu-u.ac.jp.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kimizuka
keywords: aggregation; donor-acceptor systems; photochemistry; photon upconversion; triplet-triplet annihilation