-Terphenyl linked donor-π-acceptor dyads: intramolecular charge transfer controlled by electron acceptor group tuning.

A series of -terphenyl linked donor-π-acceptor (D-π-A) dyads were prepared to understand the electronic effects of a -terphenyl linker according to the electron-accepting ability change. The energy band gaps of the dyads were controlled by tuning the accepting ability, which resulted in emission colors ranging from blue-green to red. In the Lippert-Mataga plots, intramolecular charge transfer (ICT) behavior was observed, which showed gradually increased ICT characteristics as the accepting ability was increased. On the other hand, in the absorption spectra, a red shift of the ICT transition was observed differently from the electron-accepting ability tendency. Thus, the experimental results show that the ICT is determined by steric hindrance rather than the acceptor ability in the ground state due to the lack of π-conjugation of the terphenyl linker by the electron node in the -position, whereas ICT in the excited state is controlled by electron-accepting ability.