MODIFICATION OF THE INTRAMOLECULAR ELECTRON-TRANSFER BY HYDROGEN-BONDING - 4-(DIALKYLAMINO)PYRIMIDINES

The dual fluorescence (a and b) and the picosecond kinetics of the TICT state formation in 4-(dialkylamino)pyrimidines are studied in polar solvents. In nitriles as solvents, two emitting states of 4-(N,N-dimethylamino)pyrimidine or 4-(N,N-diethylamino)pyrimidine were shown to reach equilibrium within 20 ps. In alcohols the TICT emission a is attributed to the species hydrogen-bonded at the ring nitrogen atom N1. The decay of the short wave fluorescence b is clearly multi- or non-exponential; it is assigned to several other complexes, some of which decay fast, not being simply kinetically coupled with the emitting form a. The nature of the fast deactivation channel appearing in alcohols as solvents is discussed taking into account the Mataga-Kakitani discrimination of the Marcus inverted regions for the charge recombination and charge shift electron transfer.