The fluorescence of some dipolar NN-dialkyl-4-(dichloro-1,3,5-triazinyl)anilines. Part 3. Intersystem crossing yields from intramolecular charge-transfer excited states and triplet state properties

Abstract

The phosphorescence and triplet–triplet optical absorption characteristics of NN-diethyl-4-(dichloro-1,3,5-triazinyl)aniline have been examined in rigid and fluid media. A value of 31 000 ± 5 000 dm³ mol^–1 cm^–1 has been determined for the molar extinction coefficient of the triplet–triplet absorption maxima at 490 nm of the compound dissolved in ether–pentane–alcohol (5 : 5 : 2) glass at 77 K and in poly-(methyl methacrylate) at 293 K. Intersystem crossing yields in toluene (0.10), tetrahydrofuran (0.15), n-butanol (0.14), ethanol (0.07), and acetonitrile (0.05) have been related to the quenching of fluoresence induced by polar solvent, and rationalised on the basis of a previously proposed ‘twisted intramolecular charge-transfer state’ model.

The spectral properties of other related NN-disubstituted anilines possessing an electron acceptor substituent [CO₂H, CO₂Me, CN, CHO, C₃N₃Cl(NMe₂), and NO₂] in the para-position have also been investigated.