Enhanced emission efficiency and excited state lifetime due to restricted intramolecular motion in silole aggregates

The agregation-induced emission (AIE) properties of 1,1,2,3,4,5-hexaphenylsilole(HPS)andpoly{11-[(1,2,3,4,5-pentaphenylsilolyl)oxy]-1-phenyl-1-undecyne} (PS9PA) were studied by time-resolved fluorescence technique. The enhanced fluorescence and long fluorescent lifetime were obtained for the sample in an aggregate state as compared to the sample in solution. The time-decay of fluorescence of RPS and PS9PA in high viscosity solvents and low-temperature glasses has also been measured in detail to further investigate the possible mechanism for AIE. Enhanced light emission and long fluorescence lifetime were detected for both HPS and PS9PA in the solution-thickening, and cooling experiments. These results provided direct evidence. that the enhanced photoluminescence (PL) efficiency is due to restricted intramolecular motion. which ascribes AIE to the deactivation of nonradiative decay caused by restricted torsional motions of the molecules in the solid state or aggregate form.