Triplet Excimer Formation Research Articles

Triplet state quenching by ground state molecules of the same kind. Xanthione in solution

The highly efficient quenching of thione triplet states by ground state molecules of the same kind was investigated for xanthione by means of phosphorescence lifetime measurements in a variety of solvents, in some cases as a function of temperature. The quantum yields of photodecomposition of xanthione were also determined. It is shown that the triplet quenching process is diffusion-controlled and physical in nature. The short-range quenching mechanism is suggested to involve triplet excimer formation with subsequent radiationless decay.

Triplet excimer formation and phosphorescence in fluid solutions of diarylalkanes: Excimer phosphorescence of dinaphthylalkanes and monomer phosphorescence of diphenylpropane

The excimer phosphorescence, delayed fluorescence, and triplet–triplet absorption of α,α-dinaphthylalkanes have been investigated in isooctane at several temperatures. The results are consistent with the formation of intramolecular triplet excimers whose conformation is significantly different from that favored by singlet excimers. 1,3-diphenylpropane displays only monomerlike phosphorescence in fluid media over a wide temperature range, indicating that the binding energy of this triplet excimer is considerably smaller than that for the triplet excimers of dinaphthylalkanes.

ChemInform Abstract: TRIPLET EXCIMER OF PHENANTHRENE IN FLUID SOLUTION. DYNAMIC ANALYSIS OF TIME‐RESOLVED PHOSPHORESCENCE

The excimer phosphorescence of phenanthrene in isooctane at temperatures over a range of 300–77 K has been studied by means of a photon-counting technique. At temperatures above the melting point of isooctane a broad emission spectrum with its intensity maximum at 525 nm was obtained, which is essentially different from the structured phosphorescence spectrum obtained in rigid media at 77 K. The time dependence of the spectral shape and intensity of the phosphorescence emission affords strong evidence that the broad emission spectrum originates from the triplet excimer. A scheme of the triplet excimer formation involving a self-quenching pathway of the triplet monomer is proposed to interpret the time and concentration dependence of the monomer and excimer phosphorescence.

Kinetic study of triplet excimer formation in fluid solution by means of phosphorimetry

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetic study of triplet excimer formation in fluid solution by means of phosphorimetryTakeshi Takemura, Masayuki Aikawa, Hiroaki Baba, and Yoshio ShindoCite this: J. Am. Chem. Soc. 1976, 98, 8, 2205–2210Publication Date (Print):April 1, 1976Publication History Published online1 May 2002Published inissue 1 April 1976https://doi.org/10.1021/ja00424a033RIGHTS & PERMISSIONSArticle Views170Altmetric-Citations45LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (689 KB) Get e-Alerts Get e-Alerts

Triplet Excimer of Phenanthrene in Fluid Solution. Dynamic Analysis of Time-Resolved Phosphorescence

Abstract The excimer phosphorescence of phenanthrene in isooctane at temperatures over a range of 300–77 K has been studied by means of a photon-counting technique. At temperatures above the melting point of isooctane a broad emission spectrum with its intensity maximum at 525 nm was obtained, which is essentially different from the structured phosphorescence spectrum obtained in rigid media at 77 K. The time dependence of the spectral shape and intensity of the phosphorescence emission affords strong evidence that the broad emission spectrum originates from the triplet excimer. A scheme of the triplet excimer formation involving a self-quenching pathway of the triplet monomer is proposed to interpret the time and concentration dependence of the monomer and excimer phosphorescence.

Modulation excitation spectra of some aromatic hydrocarbons at high concentration, evidence for triplet excimer formation

Modulation excitation spectra of 1:2-benzanthracene and 1:2:3:4-dibenzanthracene at very high concentration are characterized by the appearance of new broad bands, decreased lifetimes and a marked decrease in the quantum yield of the triplet state. These are interpreted as arising from triplet excimer formation.

Low temperature trapping mechanisms in molecular solids using PMDR spectroscopy. III. molecular aggregation and the formation of hexachlorobenzene triplet excimer

The triplet of hexachlorebenzene (HCB) at 1.6 K is found to form only at the defect sites of the crystal lattice. These defects can be created by introducing chemical impurities of higher field energies that of HCB, e.g., other chlorinated or methylated benzene derivatives, or by applying external pressure. The Phosphorescence-Microwave Double Resonance (PMDR) technique is used to study this broad “excimer” type emission. The followin conclusions are made: 1. Since the emission has zf transitions of energies and decay characteristics that are independent of the manner by which the defects are created, it is concluded that the emission must be due to a species involving HCB itself. 2. Since the emission is not observed in undoped pure HCB crystals and its emission intensity is independent of the UV radiation exposure time, it is believe that the emissions is not originated from photochemical products. 3. The observed band width of the zf absorptions and the chlorine quadrupole splittings are similar to those found for the monomer species of HCB and other chlorobenzenes, suggesting that the excited triplet state is not dissociative. The observed diffuseness of the optical spectrum is thus explained in terms of a repulsive ground state potential, thus supporting the assignment of an “excimer” type species. Temperature effects of the HCB triplet excimer emission spectra have been examined from 1.6 to 65 K. The following results are obtained: 1. At temperature higher than 8 K, two new emission maxima appear, replacing the old one in the optical spectrum. This is explained in terms of either the formation of two new excimers of different configurations or emission from vibrationally excited excimer. 2. The intensity of the excimer emission is found to decrease as the temperature increases with an activation energy of 20 cm −1 (which is of magnitude of the frequency of some lattice vibrations). 3. The fact that the emission lifetime decreases at a much slower rate than the emission intensity suggests that the decrease in intensity with temperature is a result of annealing the chemically induced defects and thus decreasing the rate of formation of the excimer. Polarization and lifetimes of the phosphorescence from the individual magnetic sublevels of HCB triplet excimer are determined experimentally. The polarization is predicted group theoretically for both types of excimers made of the translationally “equivalent” and “inequivalent” HCB molecules in the crystal. The results are consistent with an excimer formed from translationally equivalent HCB molecules in the crystal. Using phosphorescence microwave photoexcitation spectroscopy, it was further concluded that the excimer is formed as a result of trapping HCB triplet-rather than singlet-excitons.

Photophysical processes in the vapour-phase measured by the optic-acoustic effect. Part 3.—Radiationless processes from the lowest singlet and triplet states of [1H6]benzene and [2H6]benzene

Optic-acoustic measurements on the triplet state relaxation of [1H6] benzene and [2H6] benzene are described. The respective triplet deactivation rates in s–1 are 1.7 × 103+ 6.6 × 107[C6H6] and 1.9 × 103+ 2.1 × 107[C6D6] with [C6H6][C6D6] in mol dm–3. The concentration dependent term is discussed in terms of triplet excimer formation which may facilitate the passage through an isomeric intermediate to ground state benzene. For excitation at 40400 cm–1 the triplet quantum yield tends to zero at zero pressure. An explanation of this is given, not involving reversible radiationless processes, but in terms of both pressure-dependent and pressure-independent internal conversion rates out of the vibrationally excited singlet state. With this model internal conversion rates in s–1 are 1.7 × 107+ 1.5 × 1010[C6H6] and 1.3 × 107+ 1.3 × 1010[C6D6] for excitation at 40400 cm–1.

Triplet-state lifetime of vapour-phase benzene

A technique based on the optic-acoustic effect has been used to measure the triplet state lifetime of benzene over a range of pressure. The rate-constant for the deactivation of the triplet state by collisions with ground-state benzene is 1.1 × 10 −13 sec −1 cm 3 molecule −1, which corresponds to a collisional efficiency of 1.6 × 10 −4, and the pressure-independent radiationless rate-constant is approximately 1.7 × 10 3 sec −1. The collisional efficiency is discussed in terms of triplet excimer formation.

Photochemistry of ketones in solution. XXXVII. Flash photolysis of Michler's ketone in solution. Rate constants for decay and triplet excimer formation

Photochemistry of ketones in solution. XXXVII. Flash photolysis of Michler's ketone in solution. Rate constants for decay and triplet excimer formation