Star-shaped donor-pi-acceptor conjugated molecules: synthesis, properties, and modification of their absorptions features.

Well-defined star-shaped donor-pi-acceptor meta-conjugated systems with broad absorption features were constructed through facilely synthetic routes, in which triphenylamine (TPA) moiety as an electron donor and 2-dicyanomethylen-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) unit as an electron acceptor were introduced in various ratios. The investigation of the photophysical properties indicated that the absorption bands of these compounds covered the whole visible range from 300 to 800 nm. For instance, the absorption onset of D1A2T2 was located at about 780 nm and peaked at 606 nm in thin film. The steady and transient emission spectra showed that these compounds possess an intramolecular energy transfer in such a meta-conjugation system, which was further supported by our computational investigation. Our systematic structural variation provides us insight into the tuning strategy of optical properties in D-pi-A systems and offered us a series of broad absorption molecules.