Color-tuning aggregation-induced emission of o-Carborane-bis(1,3,5-triaryl-2-pyrazoline) triads: Preparation and investigation of the photophysics

Abstract

Four D−A−D triads with an o-Carborane moiety as the electron acceptor and 1,3,5-triaryl-2-pyrazoline as the electron donor were designed and synthesized via a novel nickel-catalyzed cross-coupling reaction. The four triads exhibited aggregation-induced emission (AIE) attributes. The photophysical properties and crystal packing structures of these compounds were systematically investigated by UV-Vis absorption and fluorescence spectroscopy, time-resolved fluorescence, X-ray crystallography, CV and DFT theoretical calculations. The photoluminescence spectra showed bathochromic shift (λmax = 596–638 nm) with the increase of electron-donating ability of the substituents and accompanied systematic color-tuning from yellow to bright red with high fluorescence quantum yield (35.7%) in the solid state. The AIE mechanism could be attributed to the restriction of molecular motions and Cc–Cc bond vibration in o-Carborane which enhanced the intramolecular charge transfer (ICT) of the o-Carborane-bis(1,3,5-triaryl-2-pyrazoline) derivatives. DFT calculation further demonstrated that substituent variation is a possible way for precise color-control of AIE.