The charge distribution, molecular structure, and morphological packing significantly affect the photophysical properties of organic photoluminescent materials. In this work, two triphenylpyrrole isomers, 1,2,5- (TPP1) and 1,3,4- (TPP2), were first synthesized and characterized. Because of their different substituent positions, TPP1 possesses aggregation-caused emission quenching (ACQ) behavior while TPP2 exhibits aggregation-induced emission (AIE). Their different photoluminescent properties were systematically investigated by using UV–vis absorption spectroscopy, fluorescence spectroscopy, density functional theory (DFT) calculations, and single-crystal structure analysis. The results indicate that substituent position of the two phenyl groups predominately affects the charge distribution of the isomers and determines their molecular packing structures, which further cause the different restriction of intramolecular rotation (RIR) capabilities of phenyl rings, thus resulting in different luminescence properties of these two triphenylpyrrole isomers under different aggregate states.

Eight donor-π-acceptor (D-π-A) compounds employing triphenylpyrrole isomers (TPP-1,2,5 and TPP-1,3,4) as donors, malononitrile (CN) and 1H-indene-1,3(2H)-dione (CO) as acceptors, pyridone (P) and benzopyran (B) as π-linking groups were synthesized. The compounds exhibited aggregation-induced emission and piezochromic properties. Compared with previously reported donors, triphenylpyrroles induced all the compounds to have more remarkable photophysical properties. The compounds containing TPP-1,2,5 and P moieties displayed stronger fluorescence intensities, shorter emission wavelengths, and more distinct piezochromic properties. However, the same phenomenon was observed in the TPP-1,3,4-containing system if B was as π-linker. Moreover, the CN acceptor endowed the compound to have a relatively strong fluorescent intensity, in which CO induced a relatively long emission wavelength. That is, the photophysical properties of D-π-A compounds can be controlled by adjusting the structure of donor, linker and acceptor.

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