scholarly journals Triplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophores

2016 ◽  
Vol 7 (6) ◽  
pp. 3621-3631 ◽  
Author(s):  
Seda Cekli ◽  
Russell W. Winkel ◽  
Erkki Alarousu ◽  
Omar F. Mohammed ◽  
Kirk S. Schanze
Keyword(s):  
Excited State ◽  
Intersystem Crossing ◽  
Triplet Excited State ◽  
Acceptor Interaction ◽  
Donor Acceptor

Intersystem crossing in π-conjugated donor–acceptor–donor chromophores is controlled by the strength of the donor–acceptor interaction.

Spin–orbit charge transfer intersystem crossing in perylenemonoimide–phenothiazine compact electron donor–acceptor dyads

2018 ◽  
Vol 54 (87) ◽  
pp. 12329-12332 ◽  
Author(s):  
Yingjie Zhao ◽  
Ruomeng Duan ◽  
Jianzhang Zhao ◽  
Chen Li
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Electron Donor ◽  
Intersystem Crossing ◽  
Spin Orbit ◽  
Triplet Excited State ◽  
Donor Acceptor ◽  
State Production

Efficient triplet excited state production (57%) was observed for perylenemonoimide–phenothiazine compact electron donor–acceptor dyads based on spin–orbit charge transfer ISC.

The mechanism of the photochemical cycloaddition reaction of N-benzoylindole with cyclopentene

1990 ◽  
Vol 68 (10) ◽  
pp. 1685-1692 ◽  
Author(s):  
Bimsara W. Disanayaka ◽  
Alan C. Weedon
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Ground State ◽  
Mechanistic Model ◽  
Cycloaddition Reaction ◽  
Intersystem Crossing ◽  
Triplet Excited State ◽  
Excited State Lifetime ◽  
Yield Data ◽  
Counting Procedure

The mechanism of the photochemical cycloaddition reaction between N-benzoylindole, 1, and cyclopentene to give cyclobutane adducts 2 and 3 has been examined. The triplet excited state lifetime and quantum yield of intersystem crossing were determined for 1 as (2.8 ± 0.3) × 10−8 s and 0.39 ± 0.01, respectively, using the triplet counting procedure. In addition, the dependence of the quantum yield of cycloadduct formation upon the concentration of cyclopentene and upon the concentration of excited state quenchers has been determined. The results are used to propose a mechanistic model in which the triplet excited state of 1 reacts with cyclopentene to give a triplet 1,4-biradical intermediate. Following spin inversion the biradical intermediate reverts to the ground state starting materials or proceeds to the products 2 and 3; this partitioning, along with the quantum yield of intersystem crossing, gives rise to a limiting quantum yield of cycloaddition at infinite alkene concentration of 0.061. It is calculated that 84% of the biradical intermediates revert to the starting materials and 16% proceed to cycloadducts. The quantum yield data are also used to calculate two independent values of the rate constant for reaction of the triplet excited 1 with alkene; the values are (1.8 ± 0.1) × 107M−1 s−1 and (4.0 ± 0.8) × 106 M−1 s−1'. Some evidence for self quenching of the triplet excited state of 1 by ground state 1 was also observed. The quantum yield of intersystem crossing and the triplet excited state lifetime of 1 were found to vary with the solvent used; this is discussed in terms of the possible existence of a charge transfer triplet excited state. Keywords: indole, photocycloaddition, mechanism.

Efficient intersystem crossing using singly halogenated carbomethoxyphenyl porphyrins measured using delayed fluorescence, chemical quenching, and singlet oxygen emission

2015 ◽  
Vol 17 (43) ◽  
pp. 29090-29096 ◽  
Author(s):  
Dawn M. Marin ◽  
Sonia Payerpaj ◽  
Graham S. Collier ◽  
Angy L. Ortiz ◽  
Gaurav Singh ◽  
...  
Keyword(s):  
Excited State ◽  
Singlet Oxygen ◽  
State Formation ◽  
Delayed Fluorescence ◽  
Intersystem Crossing ◽  
Fluorescence Lifetimes ◽  
Triplet Excited State

Singly halogenated carbomethoxyphenylporphyrins show decreased singlet fluorescence lifetimes and increased rates of triplet excited state formation.

scholarly journals Making triplets from photo-generated charges: observations, mechanisms and theory

2020 ◽  
Vol 19 (2) ◽  
pp. 136-158 ◽  
Author(s):  
Dáire J. Gibbons ◽  
Aram Farawar ◽  
Paul Mazzella ◽  
Stéphanie Leroy-Lhez ◽  
René M. Williams
Keyword(s):  
Excited State ◽  
Electron Donor ◽  
Charge Recombination ◽  
Triplet Excited State ◽  
Spin Flip ◽  
Donor Acceptor ◽  
A Charge

Photo-excitation of electron donor–acceptor systems can lead to the generation of a charge separated state (CT). Sometimes the charge recombination occurs mainly to the local triplet excited state (T1). How does the spin flip?

Exclusive triplet electron transfer leading to long-lived radical ion-pair formation in an electron rich platinum porphyrin covalently linked to fullerene dyad

2020 ◽  
Vol 56 (45) ◽  
pp. 6058-6061 ◽  
Author(s):  
Dili R. Subedi ◽  
Habtom B. Gobeze ◽  
Yuri E. Kandrashkin ◽  
Prashanth K. Poddutoori ◽  
Art van der Est ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Ion Pair ◽  
Pair Formation ◽  
Triplet Excited State ◽  
Ion Pair Formation ◽  
Donor Acceptor ◽  
Platinum Porphyrin ◽  
Covalently Linked ◽  
Pair Energy

Radical ion-pair energy as high as 1.48 eV with lifetime as much as ∼1 μs, exclusively from the triplet excited state of a photosensitizer, is established in a novel donor–acceptor conjugate.

Electron-Phonon Coupling and CT-Character in the lowest Triplet Excited State of Anthracene EDA-Complex Crystals

1987 ◽  
Vol 42 (11) ◽  
pp. 1261-1265 ◽  
Author(s):  
S. Maier ◽  
H. Port
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Spectral Resolution ◽  
High Spectral Resolution ◽  
Phonon Coupling ◽  
Triplet Excited State ◽  
Electron Phonon Coupling ◽  
Donor Acceptor ◽  
Eda Complex ◽  
Complex Crystals

Photoexcitation spectra of triplet (T1← S0) zero-phonon lines and phonon sidebands in different anthracene electron donor-acceptor (EDA) complex crystals (A-PMDA, A-TCNB, A-TCPA) have been analyzed between 1.3 K and 50 K at high spectral resolution. From the electron-phonon coupling strength at T = 0 K values of the charge-transfer (CT) character in the range between 6% and 10% are calculated. The differences in these values are found to be correlated with the energetic positions of the triplet state, which are explained within the framework of the Mulliken theory.

Long-lived charge-separated states of simple electron donor-acceptor dyads using porphyrins and phthalocyanines

2008 ◽  
Vol 12 (09) ◽  
pp. 993-1004 ◽  
Author(s):  
Kei Ohkubo ◽  
Shunichi Fukuzumi
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Electron Donor ◽  
Driving Force ◽  
Reorganization Energy ◽  
Charge Recombination ◽  
Zinc Phthalocyanine ◽  
Intramolecular Electron Transfer ◽  
Triplet Excited State ◽  
Donor Acceptor

Control of electron-transfer processes is described for a number of electron donor-acceptor dyads containing porphyrins or phthalocyanines as models for the photosynthetic reaction center. The rates for intramolecular electron transfer in the dyads are controlled by the driving force and reorganization energy of electron transfer. The small reorganization energy of electron transfer reactions and large driving force of charge recombination are required to form long-lived charge-separated states. A directly linked zinc chlorin-fullerene dyad, especially, has the longest lifetime of charge-separated state at 120 s at -150 °C, which is a much longer lifetime and higher energy than those of natural photosynthetic reaction centers. On the other hand, the charge-separated states of the phthalocyanine-based donor-acceptor dyads (silicon phthalocyanine-fullerene, and zinc phthalocyanine-perylenebisimide) are short-lived since charge recombination forms the low-lying triplet excited state of the chromophore. The energy of the charge-separated state of a zinc phthalocyanine-perylenebisimide dyad is decreased by binding of metal ions to the radical anion moiety in order to be lower than the triplet excited state. This results in formation of a long-lived charge-separated state. The mechanistic viability of formation of long-lived charge-separated states is demonstrated by a variety of examples based on the Marcus theory of electron transfer.

Sign in / Sign up

Export Citation Format

Share Document