Synthesis, photoluminescence, chromogenic and fluorogenic discrimination of fluoride and cyanide based on a triphenylamine-tri(2-formyl BODIPY) conjugate

Abstract

A triphenylamine-decorated BODIPY conjugate (TPA-BODIPY) containing three 2-formyl BODIPY units at one triphenylamine core with electron donor-acceptor structure was synthesized. TPA-BODIPY did not show a twisted intramolecular charge transfer (TICT) effect, possibly because its donor–acceptor effect of was partially blocked by the phenyl bridges. However, its emission can be enhanced by increasing solvent viscosity and decreasing solution temperature, indicating that the aggregation-​induced emission (AIE) effect was caused by the restriction of the intramolecular rotations of luminogens. We also discovered that TPA-BODIPY could be applied as a colorimetric and fluorescent chemosensor for F− and CN− with no interference from each other. The addition of F− and CN− to TPA-BODIPY induced a rapid color change from yellowish green to yellow and flesh, respectively. 19F, 11B and 1H NMR spectra indicated that the preferential binding of cyanide occurred at the boron center of BODIPY core not formyl group. On the other hand, fluoride binding also occurred at the boron center of BODIPY core. However, the BODIPY moiety is presumably decomposed by the cyanide anions in a different way compared to fluoride anions, which can be used as a chemodosimetric probe for F− and CN− ions.