9,10-Bis((Z)-2-phenyl-2-(pyridin-2-yl)vinyl)anthracene: Aggregation-induced emission, mechanochromic luminescence, and reversible volatile acids-amines switching

Abstract

Pyridine-containing luminophores have been attracting much attention due to pyridine functions in carrier transport and cation complexation. Here we prepared a butterfly-like molecule 9,10-bis(2-phenyl-2-(pyridin-2-yl)vinyl)anthracene (PyVA) for developing new multifunctional dyes. The multiple rotatable aryl groups enabled PyVA to exhibit a strong aggregation-induced emission effect, and the seriously twisted butterfly-like backbone rendered the solid weak intermolecular π-π interactions and mechanofluorochromism. Quantum chemical calculations indicated that protonation of the pyridyl units could narrow the band gap of PyVA, and X-ray crystallography revealed that PyVA molecules packed in a Z configuration in which the pyridyl units adopted a more twisted conformation with lone N-electron pairs stabilized by intra- and intermolecular CH···N and CH···π interactions. It was observed that both fluorescent crystalline and amorphous PyVA solids could sense volatile acids with a remarkably red-shifted emission, but the amorphous state was more sensitive. Moreover, the acidichromic PyVA solid could further sense volatile amines, and this alternative pH sensitive chromic process was reversible and applicable to fluorescence patterning.