Detection and chemistry of the triplet state of thymine

1970 ◽  
Vol 48 (4) ◽  
pp. 694-696 ◽  
Author(s):  
A. G. Szabo ◽  
W. D. Rlddell ◽  
R. W. Yip
Keyword(s):  
Excited State ◽  
Triplet State ◽  
Rate Constant ◽  
Triplet Excited State

The transient produced on flash excitation of degassed solutions of thymine in acetonitrile has been characterized as the triplet excited state of thymine. This triplet state has a lifetime of 14 ± 1 μs and the associated dimerization rate was found to be 5.3 ± 0.3 × 108 M−1 s−1. The triplet state of thymine could be quenched by 2,4-hexadien-1-ol with a rate constant of 8.1 ± 0.6 × 109 M−1 s−1.

scholarly journals Triplet energies and excimer formation in meta - and para -linked carbazolebiphenyl matrix materials

2015 ◽  
Vol 373 (2044) ◽  
pp. 20140446 ◽  
Author(s):  
Sergey A. Bagnich ◽  
Alexander Rudnick ◽  
Pamela Schroegel ◽  
Peter Strohriegl ◽  
Anna Köhler
Keyword(s):  
Excited State ◽  
Triplet State ◽  
Spectroscopic Investigation ◽  
Triplet Excited State ◽  
Conjugation Length ◽  
Triplet Energy ◽  
Excimer Formation

We present a spectroscopic investigation on the effect of changing the position where carbazole is attached to biphenyl in carbazolebiphenyl (CBP) on the triplet state energies and the propensity to excimer formation. For this, two CBP derivatives have been prepared with the carbazole moieties attached at the ( para ) 4- and 4 ′ -positions ( p CBP) and at the ( meta ) 3- and 3 ′ -positions ( m CBP) of the biphenyls. These compounds are compared to analogous m CDBP and p CDBP, i.e. two highly twisted carbazoledimethylbiphenyls, which have a high triplet energy at about 3.0 eV and tend to form triplet excimers in a neat film. This torsion in the structure is associated with localization of the excited state onto the carbazole moieties. We find that in m CBP and p CBP, excimer formation is prevented by localization of the triplet excited state onto the central moiety. As conjugation can continue from the central biphenyls into the nitrogen of the carbazole in the para -connected p CBP, emission involves mainly the benzidine. By contrast, the meta -linkage in m CBP limits conjugation to the central biphenyl. The associated shorter conjugation length is the reason for the higher triplet energy of 2.8 eV in m CBP compared with the 2.65 eV in p CBP.

Extending the scope of the carbonyl facilitated triplet excited state towards visible light excitation

2018 ◽  
Vol 20 (28) ◽  
pp. 19120-19128 ◽  
Author(s):  
Shinaj K. Rajagopal ◽  
Nagaraj K. ◽  
Somadrita Deb ◽  
Vinayak Bhat ◽  
Devika Sasikumar ◽  
...  
Keyword(s):  
Excited State ◽  
Visible Light ◽  
Triplet State ◽  
Lewis Acid ◽  
Triplet Excited State ◽  
Light Excitation ◽  
Acid Catalyzed

A series of extended π-conjugated benzophenone analogs was synthesized through a facile Lewis-acid catalyzed Friedel–Crafts reaction in order to exploit the integral triplet state properties of benzophenone.

The unquenched triplet excited state of the fluorescent OFF/ON Bodipy-derived molecular probe based on photo-induced electron transfer

2016 ◽  
Vol 15 (11) ◽  
pp. 1358-1365 ◽  
Author(s):  
Zafar Mahmood ◽  
Jianzhang Zhao
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Triplet State ◽  
Molecular Probe ◽  
Singlet Excited State ◽  
Triplet Excited State ◽  
Photo Induced Electron Transfer

Different from the singlet excited state (fluorescence), the triplet state of the probes is not quenched by photo-induced electron transfer.

scholarly journals Pump–probe XAS investigation of the triplet state of an Ir photosensitizer with chromenopyridinone ligands

2018 ◽  
Vol 17 (7) ◽  
pp. 896-902 ◽  
Author(s):  
Grigory Smolentsev ◽  
Kaj M. van Vliet ◽  
Nicolo Azzaroli ◽  
Jeroen A. van Bokhoven ◽  
Albert M. Brouwer ◽  
...  
Keyword(s):  
Excited State ◽  
Dft Calculations ◽  
Triplet State ◽  
Absorption Spectroscopy ◽  
Triplet Excited State ◽  
Pump Probe ◽  
X Ray ◽  
X Ray Absorption

The triplet excited state of a new Ir-based photosensitizer with two chromenopyridinone and one bipyridine-based ligands has been studied by pump–probe X-ray absorption spectroscopy (XANES) coupled with DFT calculations.

scholarly journals Control of triplet state generation in heavy atom-free BODIPY–anthracene dyads by media polarity and structural factors

2018 ◽  
Vol 20 (12) ◽  
pp. 8016-8031 ◽  
Author(s):  
Mikhail A. Filatov ◽  
Safakath Karuthedath ◽  
Pavel M. Polestshuk ◽  
Susan Callaghan ◽  
Keith J. Flanagan ◽  
...  
Keyword(s):  
Excited State ◽  
Triplet State ◽  
State Formation ◽  
Heavy Atom ◽  
Molecular Rotation ◽  
Structural Factors ◽  
Triplet Excited State ◽  
State Generation

Heavy atom-free BODIPY–anthracene dyads show triplet excited state formation via PeT, controlled by molecular rotation and environmental polarity.

Synthesis, photophysicochemical studies of adjacently tetrasubstituted binaphthalo-phthalocyanines

2005 ◽  
Vol 09 (05) ◽  
pp. 316-325 ◽  
Author(s):  
Itumeleng Seotsanyana-Mokhosi ◽  
Ji-Yao Chen ◽  
Tebello Nyokong
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Triplet State ◽  
Singlet Oxygen ◽  
Photophysical Properties ◽  
Zinc Phthalocyanine ◽  
Quantum Yields ◽  
Triplet Excited State ◽  
General Increase ◽  
Photochemical Behavior

Adjacent binaphthalo-phthalocyanines tetra-substituted with phenoxy (4a), 4-carboxyphenoxy (4b) and 4-t-butylphenoxy (4c) groups, as well as the di-substituted 4-carboxyphenoxy (5b) have been synthesized and characterized. The photophysical and photochemical behavior of 4a-c, were compared with those of the corresponding di-substituted derivatives, (5a-c). The secondary substituents on the phenoxy ring have an influence on the aggregation of the molecules and hence on their photophysical properties. All of the complexes exhibit a relatively good conversion of energy from the triplet-excited state to the singlet oxygen. The less aggregated molecule (4c), has the highest singlet oxygen quantum yield. For all the molecules, fluorescence yields are low and they all have relatively shorter triplet lifetimes compared with the unsubstituted zinc phthalocyanine. Increasing the number of ring substituents on these rigid MPc complexes (from complexes 5 to 4) showed a general increase in the triplet state lifetimes and singlet oxygen quantum yields, and a decrease in stability.

Stereochemical studies of the photochemical cycloaddition reaction of alkenes with N-benzoylindole and N-carboethoxyindole; evidence for biradical intermediacy

1991 ◽  
Vol 69 (7) ◽  
pp. 1171-1181 ◽  
Author(s):  
David J. Hastings ◽  
Alan C. Weedon
Keyword(s):  
Excited State ◽  
Rate Constant ◽  
Ground State ◽  
Addition Reaction ◽  
Cycloaddition Reaction ◽  
Adduct Formation ◽  
Quantum Yields ◽  
Triplet Excited State ◽  
Marked Contrast ◽  
Cis And Trans

The stereochemistries of the 2 + 2 cycloaddition products obtained from the photochemical addition reaction between N-benzoylindole or N-carboethoxyindole and the alkenes cyclopentene, cyclohexene, cycloheptene, cis- and trans-2-butene, and cis- and trans-4-octene are examined. The structures of the products are shown to be consistent with a photo-cycloaddition mechanism involving the intermediacy of triplet 1,4-biradical species. The quantum yields of adduct formation between N-benzoylindole and both cis- and trans-octene were measured as a function of alkene concentration. The results suggest that cis-octene reacts with the indole derivative's triplet excited state with a rate constant of (1.7 ± 0.3) × 107 M−1 s−1. The results are also consistent with the immediate products of this reaction being 1,4-biradicals, 98% of which revert to the ground state indole derivative and alkene, and only 2% of which proceed to cycloadduct. In marked contrast, the same treatment suggests that trans-octene reacts with the triplet excited state of N-benzoylindole with a rate constant estimated to be in the range of 1 × 106 and 6 × 105 M−1 s−1, and it appears that the 1,4-biradicals formed revert much less efficiently to the starting materials; it is estimated that between 67 and 100% of the 1,4-biradicals proceed to cycloadducts. In the reaction with cis-octene biradical reversion leads to the formation of trans-octene ("Schenk isomerization"); the quantum yield of this process is determined to be 0.074 ± 0.004, which may imply that approximately 75% of the biradicals collapse to cis-alkene and 25% collapse to the trans isomer. Key words: indole, photocycloaddition, 1,4-biradicals.

Complexation and Chiral Recognition of Chiral Binaphthyl Derivatives and β-Cyclodextrins in Solution Probed by Triplet Excited State Relaxation

2015 ◽  
Vol 229 (10-12) ◽  
Author(s):  
Yasser M. Riyad ◽  
Christian Laube ◽  
Sergej Naumov ◽  
Ralf Hermann ◽  
Bernd Abel
Keyword(s):  
Excited State ◽  
Triplet State ◽  
Supramolecular Chemistry ◽  
Chiral Recognition ◽  
Triplet Excited State ◽  
Guest Molecules ◽  
Excited Triplet ◽  
Non Covalent Interactions ◽  
Covalent Interactions ◽  
Recognition Capability

AbstractIt is well known in supramolecular chemistry that cyclodextrin host molecules (CDs) are capable of including and binding guest molecules in their hydrophobic cavities via non-covalent interactions. The unique recognition capability of CDs depends on their inherent asymmetric cavities. We explored here the impacts of the chiral recognition of excited triplet state of guest 1,1′–Binaphthyl–2,2′–diylhydrogenphosphate (BNP) enantiomers by host native

Photoreduction and light-induced triplet-state formation in a single-site fluoroalkylated zinc phthalocyanine

2014 ◽  
Vol 43 (40) ◽  
pp. 14942-14948 ◽  
Author(s):  
Hans Moons ◽  
Andrei Loas ◽  
Sergiu M. Gorun ◽  
Sabine Van Doorslaer
Keyword(s):  
Excited State ◽  
Low Power ◽  
Triplet State ◽  
State Formation ◽  
Red Light ◽  
Single Site ◽  
Zinc Phthalocyanine ◽  
Light Illumination ◽  
Triplet Excited State ◽  
Uv Illumination

Anaerobic red-light illumination leads to reduction of perfluoroisopropyl-substituted zinc(ii) phthalocyanine in ethanol, while low power UV illumination favours the formation of a triplet excited state.

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