Dual Fluorescence of 4-(Dialkylamino)pyrimidines. Twisted Intramolecular Charge Transfer State Formation Favored by Hydrogen Bond or by Coordination to the Metal Ion

Article abstract of DOI:10.1021/j100346a015

4-(N,N-dimethylamino)pyrimidine (4-DMAP) does not exhibit any markedly dual luminescence even in highly polar (aprotic) solvents, unless the ortho substituent deviates the amino group from coplanarity with the ring.Protic solvents or complexation with Zn²⁺ cause the long-wave fluorescence to appear distinctly.Contrary to 4-DMAP, 4-(N,N-diethylamino)pyrimidine (4-DEAP) reveals dual luminescence in sufficiently polar (aprotic) environment.In alcoholic solutions the intensity of the fluorescence is drastically reduced.Fluorescence properties of this group of compounds fit well to the TICT modell.The importance of nonradiative deactivation increases with the proton-donating ability of the solvent.