Intramolecular photoassociation and photoinduced charge transfer in bridged diaryl compounds. 1. Photoassociation in the lowest triplet state of 2,2'-dinaphthylmethane and 2,2'-dinaphthyl ether

Time-Resolved Emission Studies of Intermolecular Triplet Excimers in Fluid Solutions: Dibenzofuran and Dibenzothiophene Revisited

“…Apparatus and Procedures. The experimental apparatus and method employed for the time- and frequency-resolved spectral studies of the excimer formation have been described elsewhere . To measure the spectral and temporal characteristics of the laser-induced delayed emissions, the deaerated (by bubbling argon gas) fluid solution of the sample was excited by the unfocused 308 nm output (∼10 Hz) of a Lambda-Physik EMG-50 excimer laser (pulse width ∼20 ns).…”

“…The interest stems from the fact that these species are thought to be stabilized by van der Waals forces, , rather than by exciton resonance (which stabilizes singlet excimer), and hence are expected to have structures and properties that are substantially different from those of the corresponding singlet excimers. , However, because of the difficulty of distinguishing excimer phosphorescence from the impurity emission (sensitized by energy transfer from the triplet state of the compound), it has proven to be problematic to identify and characterize aromatic triplet excimers in fluid solutions. , Nonetheless, time-resolved absorption and emission studies on a number of systems provide strong evidence for the formation of triplet excimers with spectra that are distinctly different from those of the corresponding triplet monomers. The molecular systems reported to exhibit intramolecular triplet excimer formation in fluid solutions are dinaphthylalkanes, , dicarbazolylakanes, dinaphthyl ether, dinaphthylamine, naphthalene end-labeled poly(ethylene)glycol, phosphazine polymers with pendant naphthalenes, quinoxaline-annelated dimer, diphenanthrylpropane, and bis[1-(1-pyrenyl)ethyl]ether . Intermolecular triplet excimer formation in fluid solutions has been reported for carbazole, N -ethylcarbazole, dibenzofuran, dibenzothiophene, , naphthalene (for which there have been disputes ,, ), and for the neat liquid of 1-methylnaphthalene and 1-chloronaphthalene …”

“…6,7 Nonetheless, time-resolved absorption and emission studies on a number of systems provide strong evidence for the formation of triplet excimers with spectra that are distinctly different from those of the corresponding triplet monomers. The molecular systems reported to exhibit intramolecular triplet excimer formation in fluid solutions are dinaphthylalkanes, 4,8 dicarbazolylakanes, 9 dinaphthyl ether, 10 dinaphthylamine, 11 naphthalene end-labeled poly(ethylene)glycol, 12 phosphazine polymers with pendant naphthalenes, 13 quinoxaline-annelated dimer, 14 diphenanthrylpropane, 15 and bis-[1-(1-pyrenyl)ethyl]ether. 16 Intermolecular triplet excimer formation in fluid solutions has been reported for carbazole, 17 N-ethylcarbazole, 18 dibenzofuran, 17 dibenzothiophene, 17,19 naphthalene (for which there have been disputes 6,7,20 ), and for the neat liquid of 1-methylnaphthalene 21 and 1-chloronaphthalene.…”

Intramolecular photoassociation and photoinduced charge transfer in bridged diaryl compounds. 4. Temporal studies of intramolecular triplet excimer formation in dinaphthylmethanes and dinaphthyl ethers

“…It was also proposed that bimolecular annihilation of the triplet excimers leads to the formation of an intramolecular singlet excimer with a characteristic delayed fluorescence spectrum.1 •2 These molecular systems provide an interesting photophysical case in which the singlet excimer can be produced only by photoassociation in the triplet manifold and subsequent bimolecular annihilations of the triplet excimers. [1][2][3] In this paper, we present the temporal characteristics of the transient absorption and delayed fluorescence for the bridged dinaphthyls, which provide compelling kinetic evidence for the formation of intramolecular triplet excimers.…”

Intramolecular photoassociation and photoinduced charge transfer in bridged diaryl compound. 5. Intramolecular triplet excimer of 1,1'-dinaphthylamine

“…1 The fluid solutions of the samples at room temperature were degassed by continuous bubbling of Ar gas and were excited by a XeCl excimer laser. In the spectral region where delayed fluorescence appears, it was necessary to correct for the emission to record the transient absorption spectra.…”