Triplet State In Solution Research Articles

Generation and Decay Dynamics of Triplet Excitons in Alq3 Thin Films under High-Density Excitation Conditions

We studied the generation and decay dynamics of triplet excitons in tris-(8-hydroxyquinoline) aluminum (Alq3) thin films by using transient absorption spectroscopy. Absorption spectra of both singlet and triplet excitons in the film were identified by comparison with transient absorption spectra of the ligand molecule (8-hydroxyquinoline) itself and the excited triplet state in solution previously reported. By measuring the excitation light intensity dependence of the absorption, we found that exciton annihilation dominated under high-density excitation conditions. Annihilation rate constants were estimated to be gammaSS = (6 +/- 3) x 10(-11) cm3 s(-1) for single excitons and gammaTT = (4 +/- 2) x 10(-13) cm3 s(-1) for triplet excitons. From detailed analysis of the light intensity dependence of the quantum yield of triplet excitons under high-density conditions, triplet excitons were mainly generated through fission from highly excited singlet states populated by singlet-singlet exciton annihilation. We estimated that 30% of the highly excited states underwent fission.

Relative Energies and Entropies of Fullerene Triplet States in Solution

Relative Energies and Entropies of Fullerene Triplet States in Solution

High-Pressure Study on the Quenching Mechanism by Oxygen of the Lowest Triplet State in Solution

The mechanism for the quenching by oxygen of the lowest triplet state (T1) of 9-acetylanthracene(ACA) in five saturated hydrocarbon solvents at pressures up to 400 MPa was investigated. The quenching rate constants of the T1 state of ACA, kqT, decrease monotonically with increasing pressure, and the apparent activation volumes for kqT vary in the range 0.8−5.3 cm3/mol. It was also found that the plots of ln kqT against ln η, where η is solvent viscosity, show significant downward curvatures in all the solvents examined. From measurements by the time-resolved thermal lensing at 0.1 MPa, together with measurements of triplet−triplet absorption spectra as a function of pressure, the yields of the T1 state of ACA were found to be approximately unity in the experimental conditions examined. The quenching rate constants, kqS, by oxygen of the lowest excited singlet state (S1) of 9,10-dimethylanthracene (DMEA) whose van der Waals radius is nearly equal to that of ACA decrease strongly with increasing pressure, and the apparent activation volumes for kqS fall in the range of 9.4−14.9 cm3/mol. It was also found that the plots of ln kqS against −ln η are linear, with a slope of 0.59−0.71 depending on solvent. These results of kqS are consistent with our previous conclusion that the oxygen quenching of the S1 state of DMEA is diffusion controlled. The ratio, kqT/kqS, is approximately 1/9 in methylcyclohexane but is less than 1/9 in n-butane, n-pentane, n-hexane, and n-heptane at 0.1 MPa and 25 °C, and the ratio was found to increase over 1/9 with increasing pressure in all the solvents examined. By the bleaching method of DPBF, coupled with time-resolved luminescence measurements, the yields of singlet oxygen (1Δg) formed by the quenching of the T1 state of ACA, ΦΔ, were measured, and the values of ΦΔ were found to be approximately unity. These results were explained by a kinetic model in which the intersystem crossings between encounter complexes with different spin multiplicities are taken into account. From the analysis based on this model, the pressure dependence of kqT/kqS is discussed.

Spin polarization in triplet states in solution

A method is described for measuring the absolute value of the spin polarization in a triplet state in solution through CIDEP observations of the radicals formed on its reaction, and through it the anisotropy of the rates of the spin-selective intersystem crossing process. A long-accepted equation concerned with triplet mechanism spin polarization is shown to be inadequate to reproduce observed behaviour, and evidence produced to suggest that the observed polarization is affected by radical relaxation. The method also allows determination of the absolute polarization in the radicals. A novel analysis of the relative contributions of TM and RPM processes to observed spectra provides further evidence for the conclusions.

Fluorescence correlation spectroscopy of triplet states in solution: a theoretical and experimental study

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFluorescence correlation spectroscopy of triplet states in solution: a theoretical and experimental studyJerker Widengren, Uelo Mets, and Rudolf RiglerCite this: J. Phys. Chem. 1995, 99, 36, 13368–13379Publication Date (Print):September 1, 1995Publication History Published online1 May 2002Published inissue 1 September 1995https://doi.org/10.1021/j100036a009RIGHTS & PERMISSIONSArticle Views4316Altmetric-Citations594LEARN 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 (1 MB) Get e-Alerts

Absorption Spectra and Dynamics of the Triplet State in p-Terphenyl Powder Systems: a Diffuse Reflectance Laser Photolysis Study

Abstract A microcomputer-controlled nanosecond diffuse reflectance laser photolysis system was developed and applied to p-terphenyl powder systems. The triplet absorption spectrum of microcrystalline powders is broader and red-shifted compared to the molecular triplet state in solution. Possible contributions of an optical artifact and an impurity were rejected by examining powder systems doped with naphthacene and diluted with NaCl as well as poly(methyl methacrylate). p-Terphenyl adsorbed on silica gel and included in β-cyclodextrin gave different triplet spectra, which are interpreted in terms of conformational structure of p-terphenyl. Decay processes and an oxygen effect are also discussed.

ChemInform Abstract: Study of Energy Transfer from Upper Triplet States in Solution with Two‐Laser Two‐Photon Excitation

ChemInformVolume 19, Issue 29 Preparative Organic Chemistry ChemInform Abstract: Study of Energy Transfer from Upper Triplet States in Solution with Two-Laser Two-Photon Excitation W. G. MCGIMPSEY, W. G. MCGIMPSEY Div. Chem., Natl. Res. Counc. Can., Ottawa, Ont. K1A 0R6, Can.Search for more papers by this authorJ. C. SCAIANO, J. C. SCAIANO Div. Chem., Natl. Res. Counc. Can., Ottawa, Ont. K1A 0R6, Can.Search for more papers by this author W. G. MCGIMPSEY, W. G. MCGIMPSEY Div. Chem., Natl. Res. Counc. Can., Ottawa, Ont. K1A 0R6, Can.Search for more papers by this authorJ. C. SCAIANO, J. C. SCAIANO Div. Chem., Natl. Res. Counc. Can., Ottawa, Ont. K1A 0R6, Can.Search for more papers by this author First published: July 19, 1988 https://doi.org/10.1002/chin.198829087Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue29July 19, 1988 RelatedInformation

Study of energy transfer from upper triplet states in solution using two-laser two-photon excitation

Etude du transfert d'energie triplet triplet entre le biphenyle et l'acetyl-2 phenanthrene ou la xanthone

Role of contact complexes in singlet-triplet energy transfer

(T-T) energy transfer from the acceptor to donor. If the properties of the solvent cage lead to the same probability for these two energy transfer processes between donor and acceptor molecules, there should be no accumulation of triplet acceptor molecules in solution. In this case, acceptor molecules act as a catalyst leading to an increased population of triplet donor states. In addition to the above scheme of energy conversion in a contact complex, one can also expect that during the lifetime of the solvent cage only the S-T stage of electronic energy transfer will be completed. In this case the excited complex decays before the reverse T-T energy transfer from the acceptor to donor takes place and therefore there is a high probability that the unreacted triplet acceptor molecules will migrate beyond the boundary of the solvent cage. Therefore, depending on whether or not the triplet acceptor molecules are found in solution, one can make a conclusion about the number of elementary steps responsible for the electronic excitation energy conversion in a contact complex during its lifetime in the solvent cage. Answering the above-mentioned questions is important for understanding the properties of the solvent cage and mechanisms of energy conversion in excited contact complexes. Therefore, we conducted studies on decay channels for contact complexes, in which one of the partners from a pair was in the singlet excited state. In order to simplify the problem as much as possible and reduce it to considering only two processes: the S-T energy transfer from the donor to acceptor and the reverse T-T energy transfer from the acceptor to donor, the excited complex must fulfill a number of conditions. One of them is the lack of overlap between the fluorescence spectrum of donor and the absorption spectrum of acceptor. The fulfillment of this condition allows us to neglect the sing!et-singlet (from SoD to SoA) energy transfer relative to the efficiency of S-T energy transfer between donor and acceptor. Moreover, some experimental data [i] indicate that the donor triplet level TiD of the studied pair should be considerably lower than the acceptor triplet level TiA (AE T > i000 cm-i). The larger the energy difference between TiD and TiA , the higher the probability of appearance of acceptor molecules in the triplet state in solution at the expense of S-T energy transfer relative to the probability of T-T energy transfer from the donor to acceptor.

Picosecond pulse radiolysis of aromatic solutes in cyclohexane: formation of solute triplet states

Evolution of the absorption spectra due to transient species produced by the pulse radiolysis of biphenyl, pyrene, diphenylamine, and naphthalene in cyclohexane was measured over 50 ps to 3 ns. The initial (50 ps) yield of triplet is only a small fraction of the yield ( G ≈ 0.3) at 3 ns.

ChemInform Abstract: THE ROLE OF SECOND TRIPLET STATES IN SOLUTION PHOTOCHEMISTRY. 10. ENERGY TRANSFER FROM THE SECOND TRIPLET STATE OF NAPHTHALENE AND OTHER AROMATIC COMPOUNDS

Chemischer InformationsdienstVolume 8, Issue 10 Preparative Organic Chemistry ChemInform Abstract: THE ROLE OF SECOND TRIPLET STATES IN SOLUTION PHOTOCHEMISTRY. 10. ENERGY TRANSFER FROM THE SECOND TRIPLET STATE OF NAPHTHALENE AND OTHER AROMATIC COMPOUNDS C. C. LADWIG, C. C. LADWIGSearch for more papers by this authorR. S. H. LIU, R. S. H. LIUSearch for more papers by this author C. C. LADWIG, C. C. LADWIGSearch for more papers by this authorR. S. H. LIU, R. S. H. LIUSearch for more papers by this author First published: March 8, 1977 https://doi.org/10.1002/chin.197710120Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue10March 8, 1977 RelatedInformation

Triplet–triplet absorption spectra and the spectra of the photoreduced states of Rhodamine B and Rhodamine 110

Absorption spectra and extinction coefficients for triplet–triplet absorption in alcoholic solutions of Rhodamine B (R.B.) and Rhodamine 110 (R110) are presented, together with the quantum yields for production of the triplet states in solution and the first and second order rate constants for decay of triplet states in deaerated solutions. Absorption spectra for the semi-reduced forms of the dyes are also reported.

Nuclear Spin Polarization from Triplet States in Solution

AbstractProton and fluorine spin polarizations in solutions of optically excited p‐benzoquinones are shown to stem from the triplet states of the quinones. The phenomenon is analogous to the Optical Nuclear Polarization (ONP) effect in solids. ONP in solution is detected only if the relaxation processes among the triplet sublevels cannot destroy the polarization during the lifetimes of the triplets totally. The quinones are unique in having extremely short lived triplets. Therefore, ONP can be detected in their ground states by high resolution nmr, which allows to map out the electron distribution of the triplet states.

ChemInform Abstract: THE ROLE OF SECOND TRIPLET STATE IN SOLUTION PHOTOCHEMISTRY PART 7, MORE ON THE SECOND TRIPLET STATES OF ANTHRACENES IN SENSITIZED REACTIONS OF OLEFINS, EVIDENCE AGAINST THE SINGLET‐TRIPLET ENERGY‐TRANSFER PROCESS

Chemischer InformationsdienstVolume 4, Issue 49 Preparative Organic Chemistry ChemInform Abstract: THE ROLE OF SECOND TRIPLET STATE IN SOLUTION PHOTOCHEMISTRY PART 7, MORE ON THE SECOND TRIPLET STATES OF ANTHRACENES IN SENSITIZED REACTIONS OF OLEFINS, EVIDENCE AGAINST THE SINGLET-TRIPLET ENERGY-TRANSFER PROCESS ROGER O. CAMPBELL, ROGER O. CAMPBELLSearch for more papers by this authorR. S. H. LIU, R. S. H. LIUSearch for more papers by this author ROGER O. CAMPBELL, ROGER O. CAMPBELLSearch for more papers by this authorR. S. H. LIU, R. S. H. LIUSearch for more papers by this author First published: December 4, 1973 https://doi.org/10.1002/chin.197349151Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume4, Issue49December 4, 1973 RelatedInformation

Quenching of aromatic triplet states in solution by nitric oxide and other free radicals

The rate constants for quenching of aromatic hydrocarbon triplets by nitric oxide and by the free radical di-t-butyl nitroxide have been measured by the laser flash photolysis technique. For low energy triplets the efficiency of quenching is inversely proportional to triplet energy. At high triplet energy the rates are proportional to triplet energy and there is a large effect of solvent polarity.These data are analysed in terms of an enhanced intersystem crossing process catalysed by the doublet state nitric oxide molecule. The data are shown to be consistent with important contributions from charge-transfer interactions for high triplet energy compounds in non-polar solvents.

Oxygen quenching of aromatic triplet states in solution. Part 2

Recent measurements of the quenching of aromatic triplet states by oxygen are discussed. The dependence of the quenching rate constant on triplet energy is analysed in terms of a nonradiative transition within the collision complex between a ground state oxygen and a triplet state aromatic molecule. The Franck-Condon factor and electronic matrix element for this transition are considered. It is shown that the data are consistent with symmetry restrictions in the formation of 1∑+g oxygen. Quantum yields of 1∑+g formation are calculated from the observed quenching rate constants and compared with experiment.

Oxygen quenching of aromatic triplet states in solution. Part 1

The rate constants for oxygen quenching of aromatic hydrocarbon triplets have been measured by the laser flash photolysis technique. The quenching of high triplet energy compounds is characterised by rates which are inversely proportional to triplet energy. The reaction probabilities, which are as small as 10–2 in hexane, have been found to increase in polar or viscous solvents. Molecules with low triplet energies are quenched at one-ninth the measured diffusion controlled encounter rate.These data are analysed in terms of the non-radiative transitions of a collision complex of the aromatic triplet and ground state oxygen. The importance of restrictive Franck–Condon factors which are determined by the hydrocarbon is discussed. The data are shown to be consistent with electronic matrix elements for the energy transfer quenching processes that are dependent on orbital symmetry matching and charge transfer interactions.

Nanosecond Pulse Radiolysis of Polystyrene and Poly(methylmethacrylate)

Polystyrene and poly(methylmethacrylate) (PMMA) containing diphenyl and naphthalene as solutes have been studied by nanosecond pulse radiolysis. Solute negative ions were detected in PMMA but not in polystyrene. Solute triplet states were formed in times short compared with the lifetimes of the solute excited singlet states, whose presence was observed via their fluorescence. G (triplet) values of 0.2M samples of naphthalene and diphenyl in polystyrene were estimated to be 1.7 and 1.3, respectively. It is also shown that for high concentrations of solute less than 25% of the solute triplet states is derived from ion neutralization inside the spur. No evidence of intersystem crossing from solute excited singlet states was observed. Triplet yields in PMMA were smaller than those in polystyrene by a factor of 2 or more and were strongly affected by other transient species accumulated in previous irradiations. This latter quenching mechanism appears to involve the precursor, rather than the solute triplet states themselves. Possible modes of solute triplet-state formation are discussed, and it is concluded that triplet energy transfer from the solvent is the most probable mechanism.

Formation of excited states in the pulse radiolysis of solutions of aromatic compounds in cyclohexane and benzene

Measurements have been made on the triplet absorptions produced on irradiation of solutions in cyclohexane and benzene. Triplet yields were determined using the most recent extinction coefficient estimates. The yields were: anthracene; in cyclohexane, G= 0.2 (10–4 M) to G= 1.05 (10–2 M); in benzene, G= 0.15 (10–4 M) to G= 1.5 (5 × 10–3 M). Naphthalene; in cyclohexane, G= 0.25 (10–4 M) to G= 2.4 (9 × 10–1 M); in benzene, G= 0.4 (10–3 M) to G= 2.3 (1 M). Benzophenone; in cyclohexane (ketyl radical); in benzene, G= 0.4(10 –3 M)to G= 2.3 (1 M). Benzophonone; in cyclohexane (ketyl radical); G= 0.4 (10 –4 M) to G= 4.8 (1 M); in these solutions. Dilute nepthalene in cyclohexane and benzene gave monomer fluorescence but at higher concentrations emission due to excimer was also seen. Allowing for excimer formation, the concentration dependence of fluorescence in cyclohexane was similar to that of the triplet states. In benzene the rise in napthalene fluorescence was less than the rise in triplet yield. For cyclohexane solutions, solute triplet states are believed to be formed mainly through neutralization of solute ions, some directly, and some via the intermediate formation of solute singlet states. A similar mechanism may operate in concentrated solutions in benzene, but in dilute solutions, solute triplets may also be formed via singlet and triplet states of the solvent.

On the Degassing of Solutions for Luminescence and other Studies

In a recent paper Jackson, Livingston and Pugh (1) suggest that the greatest difficulty in studies of triplet states in solution is the chemical one of obtaining pure solvents. A second source of difficulty in studying both singlet and triplet states in solution is the necessity of the complete removal of dissolved oxygen because of its high quenching efficiency (2-4). Using luminescence measurements, we have been able to show that even careful degassing procedures can introduce impurities into originally