Synthesis of 1, 2, 5-triphenyl-pyrrole and effect of its aggregation degree on photoluminescence intensity

2, 5-triphenylpyrrole (TPP) was firstly prepared by the Schulte-Reisch reaction of 1, 4-diphenylbuta-1, 3-diyne with aniline catalyzed by copper chloride. Compared to solution reaction in DMF as solvent, the bulk reaction modified in this paper not only increased the yield and reduced the reaction temperature, but also shortend the reaction time. The π-π stacking interaction and the restriction of intramolecular rotation are were involved at the same time when TPP was aggregated in the THF-water mixtures. When the water volume fraction was under 60%, the PL intensity of TPP was independent on the water fraction in THF-water mixture. When the water fraction was added to 70%, which induced the non-tight aggregation of TPP, the strong π-π stacking interaction toned the nonradiative deactivation process and led to quenching the fluorescence of TPP; if the water fraction was further increased to 80%, which induced the tight aggregation of TPP, the restriction of intramolecular rotation was, however, preponderant over π-π stacking interaction. Thus the nonradiative channel was blocked and the photoluminescence intensity of TPP was enhanced. The compact degree of aggregation was influenced by acetonitrile solvent due to the charge transfer interaction between TPP and acetonitrile. The aggregation-induced emission enhancement of TPP in THF-water mixture disappeared in acetonitrile-water mixture.