Spectroscopic And Theoretical Studies Of 6-N,N-Dimethyladenine

In contrast to adenine, N,N-dimethylated adenine (6-N,N-dimethyladenine, DMADE) emits dual fluorescence in solvents of different polarity. The low energy band has been ascribed to emission from an intramolecular charge transfer (TICT) state, the high energy B band to a locally excited state localized mostly within the purine ring. The low-temperature measurements of the fluorescence of DMADE, as well as of that of 6-N,N-dimethyladenosine indicate that the 9H tautomer of DMADE is the main emitting species of this compound. The precursor-successor B --> A model in the kinetic range describes the emissive properties of DMADE at room temperature even in weakly polar solvents. The effective deactivation process, characteristic for nucleic acid bases, competes with the transformation to the ICT state. Theoretical computations are in good agreement with the experimental results.