Acid/Base-Controllable FRET and Self-Assembling Systems Fabricated by Rhodamine B Functionalized Pillar[5]arene-Based Host-Guest Recognition Motifs.

A novel supramolecular Föster resonance energy transfer (FRET) system was fabricated by utilizing rhodamine B (RB) functionalized pillar[5]arene (EtP5-RB) and cyano-modified boron dipyrromethene (BDP-CN) based on their host-guest recognition at 5.0 × 10-5 M, which could be turned "on" and "off" by adding trifluoroacetic acid (TFA) and triethylamine (TEA), respectively. At a higher concentration (1.0 × 10-4 M) in acetone, EtP5-RB self-assembled into vesicles while EtP5-RBH self-assembled into nanoribbons. After the addition of BDP-CN, both EtP5-RB⊃BDP-CN and EtP5-RBH⊃BDP-CN self-assembled into nanoparticles, which caused the fluorescence of the host-guest complexes to be quenched.