AN INVESTIGATION OF TRIPLET-STATES, RADICAL IONS, AND TRIPLET EXCIMERS PRODUCED BY LASER PHOTOEXCITATION OF PHENYLDIBENZOPHOSPHOLE IN FLUID SOLUTIONS AND RIGID MEDIA

Phenyldibenzophosphole (PDP), which is the phosphorus analogue of N-phenylcarbazole, yields excited singlet states, triplet states, radical cations, and anions, as well as excimeric species upon laser photoexcitation in fluid solutions or in rigid media such as polystyrene films. Delayed fluorescence occurs concurrently either by T-T annihilation or by the E-type process of thermally induced reverse intersystem crossing depending upon the solvent and the transient population of triplets. In solvents of high dielectric constant such as N,N-dimethylformamide (DMF) or ethanol/glycerol (30/70 v/v) (EtOH/glycerol), transient absorption signals due to triplet states and to radical cations and anions are observed. The purposeful introduction of electron donors or accepters enhances the transient signals due to cations or anions, respectively, when DMF is the solvent. In EtOH/glycerol triplet excimers are produced by ion recombination, but in rigid media it appears that exciton migration and trapping at excimer forming sites take place.