Tetraphenylethene–triphenylene oligomers with an aggregation-induced emission effect and discotic columnar mesophase

Abstract

Tetraphenylethene derivatives not only exhibit “aggregation-induced emission” (AIE) effects, but also can form a mesophase with a turbine-like rigid core. Here we report the synthesis of three tetraphenylethene–triphenylene oligomers 7, 8E and 8Z by a CuSO₄/sodium ascorbate catalyzed alkyne–azide cycloaddition reaction (CuAAC), and the successful separation of the cis- and trans-isomers by column chromatography. The structure and conformation of the oligomers were fully characterized. The photophysical properties were studied by using UV-vision and photoluminescent (PL) spectroscopy. The morphology of the aggregates was investigated by scanning electron microscopy (SEM), and the thermal stability and mesomorphic properties were investigated using thermal gravimetric analysis (TGA), polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The results revealed that the oligomers possess an AIE effect, but display no mesomorphism. However, 7 exhibits a hexagonal columnar mesophase when mixed with 2,4,7-trinitrofluorenone (TNF), forming a charge transfer complex.