Derivatives of 1-benzyl-4-(4-triphenylvinylphenyl) pyridinium bromide: Synthesis, characterization, mechanofluorochromism/aggregation-induced emission (AIE) character and theoretical simulations

Abstract

4-(4-triphenylvinyl phenyl) pyridine (TPEPy) was used, along with the benzile bromide derivatives, to prepare 1-benzyl-4-(4-triphenylvinyl phenyl) pyridinium bromide (1) and its derivatives by replacing the benzyl bromide with 4-cyanobenzyl bromide for 2, 4-nitrobenzyl bromide for 3 and 4-trifluoromethyl benzyl bromide for 4, respectively. The maxima of the photoluminescent (PL) spectra of the freshly prepared powder samples of 1 ~ 4 are in the range of 510nm ~ 530nm with the absolute luminescence quantum yields (ALQY) of 88.10% for 1, 4.69% for 2, 1.70% for 3 and 36.30% for 4, respectively, which would redshift to the range of 554nm ~ 571nm with ALQYs of 54.70% for 1, 41.00% for 2, 14.70% for 3 and 43.40% for 4, respectively, after they are ground. At the same time, 1 ~ 4 have no obvious PL bands in dichlormethane solution (10-5mol/L) until ≥ 80% n-hexane was added. Finally, the ground-state geometries and the UV-Vis absorption spectra of 1 ~ 4 were simulated at B3LYP/6-31G(d,p) level to theoretically explain their photophysical behaviors.