Triphenylamino -Cyanovinyl- and Cyanoaryl-Based Fluorophores: Solvatochromism, Aggregation-Induced Emission and Electrochemical Properties

A series of linear, V-shaped and branched triphenylamine/tris(biphenyl)amine-based derivatives with electron-withdrawing cyanovinyl- and phenyl-substituted conjugated branches containing either electron-donating OMe or electron-withdrawing CN end groups have been synthesized. UV/vis absorption and fluorescence emission data illustrates that introduction of the electron-donor/acceptor groups induces intramolecular charge transfer that leads to a shift of the absorption onset toward longer wavelengths. Addition of large amounts of water to solutions of triphenylamine derivative caused their emission to reach maximal intensitythese molecules all undergo aggregation-induced emission; this was confirmed by aggregation studies. All the compounds in this study present a reversible first oxidation process, the potential of which increases with the number of electron-withdrawing groups in the molecules, as was confirmed by cyclic voltammetry. Furthermore, the influence of solvent polarity on the photophysical properties was investigated. All the triphenylamine derivatives exhibit intensive intramolecular charge-transfer interactions, giving rise to a substantial extension of their absorption spectral response, which might be potentially used in efficient organic solar cells.