Intramolecular triplet energy transfer of the system having donor and acceptor at the chain ends. 2. The carbazole-naphthalene system

1992 ◽  
Vol 96 (25) ◽  
pp. 10115-10119 ◽  
Author(s):  
Hideaki Katayama ◽  
Shinzaburo Ito ◽  
Masahide Yamamoto
Keyword(s):  
Energy Transfer ◽  
Triplet Energy ◽  
Donor And Acceptor ◽  
Triplet Energy Transfer

Un exemple d'isomérisation radicalaire en chaînes: la photoinduction de l'isomérisation cis–trans de la pentène-3 one-2

1977 ◽  
Vol 55 (22) ◽  
pp. 3915-3926 ◽  
Author(s):  
Armel Rioual ◽  
André Deflandre ◽  
Jacques Lemaire
Keyword(s):  
Energy Transfer ◽  
Quantum Yields ◽  
Unsaturated Ketone ◽  
Chain Process ◽  
Triplet Energy ◽  
Low Concentrations ◽  
Energy Transfers ◽  
Donor And Acceptor ◽  
A Chain ◽  
Triplet Energy Transfer

Mechanisms of the photosensitized cis–trans photoisomerization of 3-penten-2-one which do not imply only classical triplet–triplet energy transfer are proposed; they are based upon measurements of the variations of initial quantum yields of isomerization with the initial donor and acceptor concentrations, the wavelength of excitation, and the nature of the donor and of the solvent. Carbonyl donors (acetophenone, benzophenone, acetone) induce a radical isomerization by a chain process in reducing solvents; the example of acetophenone is specially interesting. In solvents in which the donor is not photoreduced (as benzene or CCl4) classical triplet–triplet energy transfers occur. Sensitization with aromatic donors (benzene, mesitylene) proceeds through triplet–triplet energy transfer at low concentrations of the acceptor. At higher concentrations of acceptor, an exciplex is formed between the ketone and the aromatic in its singlet excited state; this exciplex is deactivated by dissociation and by causing the isomerization of the α,β-unsaturated ketone.

Mikrokristallbildung und intermolekulare Triplett-Triplett-Energieiibertragung in festen transparenten Glasern bei 77 K. Das System N-Methylcarbazol/Naphthalin / Microcrystal Formation and Intermolecular Triplet-Triplet Energy Transfer in Rigid Transparent Glasses at 77 K. The System N-Methyl-earbazole / Naphthalene

1984 ◽  
Vol 39 (5) ◽  
pp. 507-508
Author(s):  
M. Zander
Keyword(s):  
Energy Transfer ◽  
Triplet Energy ◽  
Donor And Acceptor ◽  
Triplet Energy Transfer

The efficient intermolecular triplet-triplet energy transfer between N-methylcarbazole (donor) and naphthalene (acceptor) observed at 10-2 ᴍ concentration of donor and acceptor in a rigid transparent methylcyclohexane/n-pentane glass at 77 K is shown to occur in microcrystals of the donor containing small amounts of the acceptor

On the Role of Microcrystal Formation in Intermolecular Triplet-Triplet Energy Transfer in Rigid Glasses

1983 ◽  
Vol 38 (10) ◽  
pp. 1146-1148
Author(s):  
M. Zander
Keyword(s):  
Energy Transfer ◽  
Transfer System ◽  
Triplet Energy ◽  
True Solution ◽  
Donor And Acceptor ◽  
Triplet Energy Transfer

Abstract The intermolecular triplet-triplet energy transfer system benzophenone (donor)/naphthalene (acceptor) was studied in various rigid glasses at 77 K. It is shown that energy transfer is much more efficient if the donor is present in the form of microcrystals than in the case where both donor and acceptor compound are in true solution.

scholarly journals Triplet Energy Transfer Mechanism of Ternary Organic Hybrid Thin Films of PFO/MEH-PPV/CsPbBr3 Perovskite Quantum Dots

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2094
Author(s):  
Bandar Ali Al-Asbahi ◽  
Saif M. H. Qaid ◽  
Hamid M. Ghaithan ◽  
Abdullah S. Aldwayyan
Keyword(s):  
Thin Films ◽  
Energy Transfer ◽  
Transfer Mechanism ◽  
Ternary Blend ◽  
Energy Transfer Mechanism ◽  
Triplet Energy ◽  
Blending Method ◽  
Donor And Acceptor ◽  
Hybrid Thin Films ◽  
Triplet Energy Transfer

The triplet energy transfer mechanism of novel poly(9,9-di-n-octylflourenyl-2,7-diyl) (PFO)/poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/CsPbBr3 perovskite quantum dot (PQD) hybrid thin films was comprehensively investigated. The concentrations of PFO and MEH-PPV in all the specimens were fixed, while the PQD content was varied with various weight ratios and premixed by a solution blending method before it was spin-coated onto glass substrates. The triplet non-radiative Förster resonance energy transfers (FRETs) in the PFO/MEH-PPV/PQDs ternary blend, the dual FRET from PFO to both PQDs and MEH-PPV, and the secondary FRET from PQDs to MEH-PPV were observed. The values of the Förster radius (Ro) of FRET from PFO to MEH-PPV in the presence of various PQD contents (Case I) increased from 92.3 to 104.7 Å, and they decreased gradually from 68.0 to 39.5 Å for FRET from PFO to PQDs in the presence of MEH-PPV (Case II). These Ro values in both cases confirmed the dominance of FRET in ternary hybrid thin films. Upon increasing the PQD content, the distance between the donor and acceptor molecules (RDA) and the conjugation length (Aπ) in both cases gradually decreased. The small values of Ro, RDA, and Aπ with a decrease in the energy transfer lifetime (τET) due to an increase in the PQD contents in both Cases I and II confirmed the efficient FRET in the hybrid. To prevent intermolecular transfer in PFO, the concentrations of MEH-PPV (Case I) and PQDs (Case II) should be decreased to a range of 0.57–0.39 mM and increased in the range of 1.42–7.25 mM.

scholarly journals Dexter energy transfer pathways

2016 ◽  
Vol 113 (29) ◽  
pp. 8115-8120 ◽  
Author(s):  
Spiros S. Skourtis ◽  
Chaoren Liu ◽  
Panayiotis Antoniou ◽  
Aaron M. Virshup ◽  
David N. Beratan
Keyword(s):  
Energy Transfer ◽  
Quantum Interference ◽  
Electronic Materials ◽  
Mediation Process ◽  
Triplet Energy ◽  
Orbital Symmetry ◽  
Energy Gaps ◽  
Solar Energy Harvesting ◽  
Donor And Acceptor ◽  
Triplet Energy Transfer

Energy transfer with an associated spin change of the donor and acceptor, Dexter energy transfer, is critically important in solar energy harvesting assemblies, damage protection schemes of photobiology, and organometallic opto-electronic materials. Dexter transfer between chemically linked donors and acceptors is bridge mediated, presenting an enticing analogy with bridge-mediated electron and hole transfer. However, Dexter coupling pathways must convey both an electron and a hole from donor to acceptor, and this adds considerable richness to the mediation process. We dissect the bridge-mediated Dexter coupling mechanisms and formulate a theory for triplet energy transfer coupling pathways. Virtual donor–acceptor charge-transfer exciton intermediates dominate at shorter distances or higher tunneling energy gaps, whereas virtual intermediates with an electron and a hole both on the bridge (virtual bridge excitons) dominate for longer distances or lower energy gaps. The effects of virtual bridge excitons were neglected in earlier treatments. The two-particle pathway framework developed here shows how Dexter energy-transfer rates depend on donor, bridge, and acceptor energetics, as well as on orbital symmetry and quantum interference among pathways.

Intramolecular Triplet-Triplet Energy Transfer in Short Flexible Bichromophoric Amino Acids, Dipeptides and Carboxylic Acid Diester

2004 ◽  
Vol 69 (4) ◽  
pp. 776-796 ◽  
Author(s):  
Miroslav Zabadal ◽  
Dominik Heger ◽  
Petr Klán ◽  
Zdeněk Kříž
Keyword(s):  
Amino Acids ◽  
Energy Transfer ◽  
Peptide Bond ◽  
Conformational Search ◽  
Triplet Energy ◽  
Efficient Energy Transfer ◽  
Donor And Acceptor ◽  
Ester Moiety ◽  
Dynamics Simulations ◽  
Triplet Energy Transfer

Efficiencies of the intramolecular triplet-triplet energy transfer (ITET) in various bichromophoric amino acids (glycine, valine, phenylalanine, and sarcosine), dipeptides (glycylglycine, phenylalanylphenylalanine), and a simple diester, with the benzoyl and naphthyl terminal groups serving as donor and acceptor, respectively, have been determined by the steady-state photokinetic measurements. The magnitude of the transfer rate constants (>108 s-1) and the number of bonds separating the chromophores (8 or 11 atoms) suggest a through-space exothermic exchange mechanism in all cases. The influence of interchromophore distance, the character of the connecting chain as well as of side chains, was evaluated. While the most efficient energy transfer was found in a flexible diester and in valine- and sarcosine-based molecules due to the steric effect of the side hydrocarbon groups, the benzyl groups in the phenylalanine and phenylalanylphenylalanine-based bichromophores had a suppressing effect on ITET. Rigidity of the peptide bond in short bichromophoric compounds causes that a large number of favorable geometries preexist already before excitation; thus the intramolecular processes are controlled by ground-state conformational distribution. Replacing this bond by a less rigid ester moiety would allow that certain unfavorable conformations may coil to favorable ones within the excited-state lifetime (a rotation-controlled photochemical model). Some conclusions were supported by a conformational search of the potential energy surface and molecular dynamics simulations.

Thymine Dimerization Induced by Oxidative DNA Lesions and Epigenetic Intermediates via Triplet-Triplet Energy Transfer

2020 ◽  
Author(s):  
Mauricio Lineros-Rosa ◽  
Antonio Francés-Monerris ◽  
Antonio Monari ◽  
Miguel Angél Miranda ◽  
Virginie Lhiaubet-Vallet
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Theoretical Calculations ◽  
Dna Lesions ◽  
Transient Absorption Spectroscopy ◽  
Triplet Energy ◽  
Pyrimidine Dimers ◽  
Triplet Energy Transfer ◽  
Dna Nucleobases

Interaction of nucleic acids with light is a scientific question of paramount relevance not only in the understanding of life functioning and evolution, but also in the insurgence of diseases such as malignant skin cancer and in the development of biomarkers and novel light-assisted therapeutic tools. This work shows that the UVA portion of sunlight, not absorbed by canonical DNA nucleobases, can be absorbed by 5-formyluracil (ForU) and 5-formylcytosine (ForC), two ubiquitous oxidative lesions and epigenetic intermediates present in living beings in natural conditions. We measure the strong propensity of these molecules to populate triplet excited states able to transfer the excitation energy to thymine-thymine dyads, inducing the formation of the highly toxic and mutagenic cyclobutane pyrimidine dimers (CPDs). By using steady-state and transient absorption spectroscopy, NMR, HPLC, and theoretical calculations, we quantify the differences in the triplet-triplet energy transfer mediated by ForU and ForC, revealing that the former is much more efficient in delivering the excitation energy and producing the CPD photoproduct. Although significantly slower than ForU, ForC is also able to harm DNA nucleobases and therefore this process has to be taken into account as a viable photosensitization mechanism. The present findings evidence a rich photochemistry crucial to understand DNA photodamage and of potential use in the development of biomarkers and non-conventional photodynamic therapy agents.

Sign in / Sign up

Export Citation Format

Share Document