Configuration-Controllable E/Z Isomers Based on Tetraphenylethene: Synthesis, Characterization, and Applications

Configuration-controllable
E/Z isomers based on tetraphenylethene
were prepared with a facile and effective method. First, compounds 1 and 2, configuration-controllable precursors
of E/Z isomers, were synthesized. Then, pure E/Z isomers were obtained
via Suzuki reaction, avoiding the difficulties of separation. The
conformational changes of E/Z isomers can occur through photoactivation.
Importantly, red-shifts of 66 nm from 6 (E-) to 3 (Z-) and 58 nm from 7 (E-) to 4 (Z-) were observed remarkably on the photoluminescence (PL) emission
spectra. The Z isomer showed a longer fluorescence lifetime compared
with the E isomer. The Z isomers 3 and 4 exhibited piezofluorochromism under grinding, whereas the E isomers 6 and 7 showed no such behaviors. The E isomer
has better thermal stability than the Z isomer. Lastly, graphene-like
molecules were synthesized with the FeCl3/CH3NO2 system. The E and Z isomers after oxidation showed
negligible differences in the PL emission spectra because the effective
conjugated lengths of oxidized E and Z isomers were both extended.
Furthermore, the fabricated field-effect transistors showed nice performance
with mobilities of 0.92 and 1.14 cm–2 V–1 s–1 at low operating voltages, respectively.