N, O - Chelate Fluoroborane Dyes: Synthesis, Optical Properties in Dual Aggregate State.

In this work, two novel N, O - chelate fluoroborane fluorescent dyes TN-1 and TN-2 with different substituents on indanone unit were synthesized via condensation reaction from indanone derivatives and benzo[cd]indol-2(1H)-one followed by fluorine-boron coordination reaction. To increase the solubility of dyes, TN-2-H and TN-2-M were designed and synthesized by another condensation reaction on active site of indanone unit on TN-2 with benzaldehyde derivatives. The optical properties of these compounds in different solvents and solid state were discussed. The maximum fluorescence emission wavelength is 654 nm with a fluorescence quantum yield (FQY) of 12% in toluene and the maximum solid fluorescence emission wavelength reaches 737 nm with an FQY of 3.15%. All the compounds were characterized by NMR, HRMS, UV-Vis absorption and fluorescence emission spectroscopy. TN-2-M was further characterized by single crystal diffraction analysis, and DFT calculations were used for modeling structure and spectra. It provide a theoretical basis for the design of near - infrared (NIR) dual - effect fluorescent dyes.