Solid state fluorescent functionalized-triphenylamine Bodipy detector for HCl vapor with high stability and absolute fluorescent quantum yield

A series of three new boron-dipyrromethenes bringing different functionalized triphenylamine donor Bodipy-TPA-R (R = BI, BH-OH, BH-COOH) (1-3) together with the reference compound Bodipy-TPA (0), have been synthesized and structurally characterized. Due to their same less electronic coupling between the triphenylamine donor and Bodipy acceptor in ground state and in particular the twisted intramolecular charge transfer (TICT) between them in excited state, these functionalized Bodipy derivatives exhibit similar optical properties in solution but not in the solid state owing to their differently intermolecular interaction and molecular packing associated with the diverse triphenylamine-modification. The lack of effective face-to-face pi-pi stacking interaction between Bodipy luminophores in crystalline states of 0 and 3, in combination with the restriction of the twisting motion and charge transfer between their triphenylamine moiety and Bodipy framework, results in the obvious aggregation- (AIE) and crystallization-induced emission (CIE) effect, with the absolute fluorescent quantum yield (Phi) as high as 19.47% and 12.30% for single crystals of 0 and 3, respectively. In good contrast, despite the same complete restriction of the functionalized triphenylamine donor around Bodipy acceptor, the presence of partial overlapping face-to-face pi-pi interaction between two parallel C9BN2 fluorophores leads to very low Phi being 1.37% and 3.40% for the single crystals of 1 and 2 as well as the negligible AIE effect. Moreover, the CIE-active red-emission for 3 can be switched between bright and dark states along with the change from the crystalline state to amorphous phase by heating cooling process. Notably, functionalization over triphenylamine moiety with carboxyl-benzoylhydrazone group in Bodipy-TPA-BH-COOH (3) renders this compound a good solid-state fluorescent sensor due to its fast fluorescence ON-OFF response for HCl vapor in thin film. (C) 2015 Elsevier Ltd. All rights reserved.