Theoretical and experimental study on the intramolecular charge transfer excited state of the new highly fluorescent terpyridine compound

Experimental and theoretical methods have been used to investigate the relaxation dynamics and photophysical properties of the donor–acceptor compound 4′-(4-N,N-diphenylaminophenyl)-2,2′:6′,2″-terpyridine (DPAPT), a compound which is found to exhibit efficient intramolecular charge transfer emission in polar solvents with relatively large Stokes shifts and strong solvatochromism. The difference between the ground and excited state dipole moments (Δμ) is estimated to be 13.7 D on the basis of Lippert–Mataga models. To gain insight into the relaxation dynamics of DPAPT in the excited state, the potential energy curves for conformational relaxation are calculated. From the frontier molecular orbital (MO) pictures at the geometry of the twisted ICT excited state, the intramolecular charger transfer mainly takes place from HOMO (triphenylamine) to LUMO (terpyridine) in this donor–acceptor system.