Analysis of emission spectra of 2,2 :6 ,2 -terpyridine (TP) in glass matrices at 77 K reveals interesting photophysics sensitive to phenyl 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 radiative channel, its free base form prefers non-radiative processes. Formation of a covalent hydrate of TP in neutral aqueous solution is observed which becomes deprotonated in basic solution. Protonation in an acidic medium is limited to two sites. The excited state is more planar and basic than the ground state.