Deciphering mechanism of aggregation-induced emission (AIE): Is E–Zisomerisation involved in an AIE process?

In this work, we address a mechanistic issue on AIE process and correct a long-held misconception on stilbene photoluminescence. E–Zisomerisation has been generally recognized as the cause of emission quenching in stilbene solutions. A natural question arisen from this common belief is whether suppression of E–Zisomerisation by aggregate formation in a stilbenic fluorogen system is responsible for its AIE phenomenon. Monitoring of the structural change of a stilbene derivative named 1,2-diphenyl-1,2-di(p-tolyl)ethene by NMR during UV irradiation reveals that the E–Zisomerisation is not involved in its AIE process under the normal photoluminescence spectral measurement conditions.