LUMINESCENCE STUDIES OF 2,2' 6',2''-TERPYRIDINE AND ITS PROTONATED SPECIES/

Analysis of emission spectra of 2,2': 6',2 ''-terpyridine (TP) in glas s matrices at 77 K reveals interesting photophysics sensitive to pheny l or pyridyl ring substitution in the 2,6-positions of pyridine. From the emission and absorption spectra in different solvents at 300 K, it is found that while the protonated form of TP deactivates via a radia tive channel, its free base form prefers non-radiative processes. Form ation of a covalent hydrate of TP in neutral aqueous solution is obser ved which becomes deprotonated in basic solution. Protonation in an ac idic medium is limited to two sites. The excited state is more planar and basic than the ground state.