Photon-Upconverting Ionic Liquids: Effective Triplet Energy Migration in Contiguous Ionic Chromophore Arrays.
Inspired by the bicontinuous ionic-network structure of ionic liquids (ILs), we developed a new family of photofunctional ILs which show efficient triplet energy migration among contiguously arrayed ionic chromophores. A novel fluorescent IL, comprising an aromatic 9,10-diphenylanthracene 2-sulfonate anion and an alkylated phosphonium cation, showed pronounced interactions between chromophores, as revealed by its spectral properties. Upon dissolving a triplet sensitizer, the IL demonstrated photon upconversion based on triplet-triplet annihilation (TTA-UC). Interestingly, the TTA-UC process in the chromophoric IL was optimized at a much lower excitation intensity compared to the previous nonionic liquid TTA-UC system. The superior TTA-UC in this IL system is characterized by a relatively high triplet diffusion constant (1.63×10(-6) cm(2) s(-1)) which is ascribed to the presence of ionic chromophore networks in the IL.
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).
Shota
S
Hisamitsu
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.
Nobuhiro
N
Yanai
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.
Nobuo
N
Kimizuka
chromophores; ionic liquids; luminescence; photon upconversion; triplet-triplet annihilation