Excited singlet state absorption spectra and relaxation kinetics of the azanaphthalenes

Picosecond excited-state singlet-singlet absorption spectra (S _n←S₁) and excited-state decay kinetics are reported for several diazanaphthalenes and a triazanaphthalene in room temperature solution. New S_n (¹nπ*) state energies are obtained empirically from these spectra. INDO-PSDCI molecular orbital calculations are used to confirm the S_n←S₁ nature of the excited state transitions observed. Decay rates are calculated from models based on a semiempirical molecular orbital formalism, and these calculated rates are compared with the observed ones. Agreement of the calculated and observed rates are good except in cases of substantial nπ*-ππ* mixing of the actual excited states and in a particular case of high molecular symmetry (1,5-naphthyridine).