Push–Pull Bisnaphthyridylamine Supramolecular Nanoparticles: Polarity-Induced Aggregation and Crystallization-Induced Emission Enhancement and Fluorescence Resonance Energy Transfer |
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| Authors: | Ryusuke Hagihara Dr Tomohiro Umeno Dr Shoji Ueki Dr Daisuke Yoshihara Dr Yasufumi Fuchi Dr Kazuteru Usui Masaomi Sakuma Prof Dr Ken-ichi Yamada Prof Dr Satoru Karasawa |
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| Institution: | 1. Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582 Japan;2. Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3-3165 Higashi-Tamagawagakuen, Machida, Tokyo, 194-8543 Japan;3. Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki City, Kagawa, 769-2193 Japan;4. Materials Open Laboratory (BUNSEKI-NEXT), Institute of Systems Information Technologies and Nanotechnologies (ISIT), 4-1 Kyudaishinmachi, Nishi-ku, Fukuoka, 819-0388 Japan |
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| Abstract: | Emissive push–pull-type bisnaphthyridylamine derivatives ( BNA-X : X=Me, Et, Bzl, Ph, BuBr, and BuTEMPO) aggregate in aqueous methanol. Furthermore, a two-step emission and aggregation process is controllable by varying the methanol-to-water ratio. At 2:3 MeOH/H2O, crystallization-induced emission enhancement (CIEE) occurs via formation of an emissive crystal phase, whereas, at 1:9 MeOH/H2O, aggregation-induced emission enhancement (AIEE) occurs, induced by emissive supramolecular nanoparticles (NPs). For BNA-Ph , the emission quantum yield was 25 times higher in aqueous methanol than that in pure methanol. Despite the high hydrophobicity of BNA-X (C log P=6.1–8.0), the spherical NPs were monodisperse (polydispersity indices <0.2). Moreover, the emissive NPs exhibited fluorescence resonance energy transfer (FRET) with pyrene; however, for BNA-X bearing the TEMPO radical ( BNA-BuTEMPO ), no FRET was observed because of quenching. In particular, the BNA-BuTEMPO NPs have a slow rotational correlation time (1.3 ns), suggesting applications as magnetic resonance imaging contrast agents with large relaxivity. |
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| Keywords: | emission fluorescence FRET nanoparticles radicals |
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