Push–Pull Bisnaphthyridylamine Supramolecular Nanoparticles: Polarity-Induced Aggregation and Crystallization-Induced Emission Enhancement and Fluorescence Resonance Energy Transfer

Ryusuke Hagihara, Tomohiro Umeno, Shoji Ueki, Daisuke Yoshihara, Yasufumi Fuchi, Kazuteru Usui, Masaomi Sakuma, Ken ichi Yamada, Satoru Karasawa

Research output: Contribution to journalArticlepeer-review

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.

Original languageEnglish
Pages (from-to)3039-3046
Number of pages8
JournalChemistry - A European Journal
Volume27
Issue number9
DOIs
Publication statusPublished - Feb 10 2021

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Organic Chemistry

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