Solvent-induced MultiStimuli-Responsive properties of cyano-substituted Oligo(p-phenylene vinylene) derivatives

Abstract

Stimuli-responsive luminescent materials with controllable photophysical properties have attracted much attention because of their potential applications in smart materials and devices. Through the incorporation of electron-donating (NPh3) and electron-withdrawing (CN) functionalities, two donor-acceptor luminophores C4OPV-TPA and C8OPV-TPA bearing two different alkyl chain lengths were prepared and fully characterized. Although both C4OPV-TPA and C8OPV-TPA exhibited similar luminescence and AIEE effects in solution with intramolecular charge-transfer (ICT) transition, remarkable differences were observed in the self-assemble state. Specifically, precipitation of C4OPV-TPA into toluene and CH2Cl2, respectively, afforded two distinctly crystallines, with one in orange color (O-state) and the other in red color (R-state). Notably, C4OPV-TPA in O-state exhibited stimuli-responsive behaviors in solid state, which were ascribed to the formation of an inclusion complex with toluene molecules. Under thermal heating and mechanical grinding, toluene was released from crystal lattice of luminophore accompanied with red-shifted emission spectra. The molecular packing of C4OPV-TPA in R-state, on the other hand, adopted stronger H-aggregates without inclusion of CH2Cl2 molecules, which was further investigated by X-ray diffraction. These excellent optical properties enabled C4OPV-TPA serve as a fluorescent ink for thermal-responsive data storage device.