Excited state lifetime and intersystem crossing rate of asymmetric pentaazadentate porphyrin-like metal complexes

2004 ◽  
Vol 84 (25) ◽  
pp. 5174-5176 ◽  
Author(s):  
Clare C. Byeon ◽  
Michael M. McKerns ◽  
Wenfang Sun ◽  
Thomas M. Nordlund ◽  
Chris M. Lawson ◽  
...  
Keyword(s):  
Excited State ◽  
Metal Complexes ◽  
Intersystem Crossing ◽  
Excited State Lifetime

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.

scholarly journals Configuration mixing upon reorganization of dihedral angle induces rapid intersystem crossing in organic photoredox catalyst

2020 ◽  
Vol 22 (23) ◽  
pp. 13292-13298
Author(s):  
Hwon Kim ◽  
Gregory D. Scholes
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Dihedral Angle ◽  
Intersystem Crossing ◽  
Excited State Lifetime ◽  
Configuration Mixing

A long excited state lifetime is a desirable quality of photocatalysts because it enables a higher probability of energy or electron transfer from the photocatalyst to a substrate.

Spin-Forbidden Excitation Enables Infrared Photoredox Catalysis

2020 ◽  
Author(s):  
Tomislav Rovis ◽  
Benjamin D. Ravetz ◽  
Nicholas E. S. Tay ◽  
Candice Joe ◽  
Melda Sezen-Edmonds ◽  
...  
Keyword(s):  
Excited State ◽  
Ground State ◽  
Intersystem Crossing ◽  
Photoredox Catalysis ◽  
Infrared Irradiation ◽  
Triplet Excitation ◽  
New Family ◽  
Ir Light

We describe a new family of catalysts that undergo direct ground state singlet to excited state triplet excitation with IR light, leading to photoredox catalysis without the energy waste associated with intersystem crossing. The finding allows a mole scale reaction in batch using infrared irradiation.

scholarly journals Impact of the Dynamic Electron Correlation on the Unusually Long Excited-State Lifetime of Thymine

2021 ◽  
pp. 4339-4346
Author(s):  
Woojin Park ◽  
Seunghoon Lee ◽  
Miquel Huix-Rotllant ◽  
Michael Filatov ◽  
Cheol Ho Choi
Keyword(s):  
Excited State ◽  
Electron Correlation ◽  
Excited State Lifetime

Measurement of excited-state lifetime using two-pulse photon echoes in rubidium vapor

2007 ◽  
Vol 24 (3) ◽  
pp. 671 ◽  
Author(s):  
E. A. Rotberg ◽  
B. Barrett ◽  
S. Beattie ◽  
S. Chudasama ◽  
M. Weel ◽  
...  
Keyword(s):  
Excited State ◽  
Excited State Lifetime ◽  
Rubidium Vapor ◽  
Photon Echoes ◽  
Pulse Photon

scholarly journals Excited State Lifetime Measurements in Rare Earth Nuclei with Fast Electronics

2011 ◽  
Vol 312 (9) ◽  
pp. 092062 ◽  
Author(s):  
V Werner ◽  
N Cooper ◽  
M Bonett-Matiz ◽  
E Williams ◽  
J-M Régis ◽  
...  
Keyword(s):  
Rare Earth ◽  
Excited State ◽  
Excited State Lifetime ◽  
Lifetime Measurements ◽  
Rare Earth Nuclei

INTERSYSTEM CROSSING OF THE ELECTRONICALLY EXCITED DIDEUTEROETHYLENE MOLECULES FORMED IN BENZENE PHOTOSENSITIZATION

1966 ◽  
Vol 44 (18) ◽  
pp. 2173-2180 ◽  
Author(s):  
Terumi Terao ◽  
Shun-Ichi Hirokami ◽  
Shin Sato ◽  
R. J. Cvetanović
Keyword(s):  
Excited State ◽  
Experimental Evidence ◽  
Rate Constants ◽  
Intersystem Crossing ◽  
Molecular Decomposition ◽  
Electronically Excited

Experimental evidence is presented for a rapidly occurring intersystem crossing of the electronically excited dideuteroethylene molecules initially formed in the benzene-photosensitized reaction at 2 537 Å and 25 °C to another excited state which is responsible for the internal H-atom scrambling. The mechanism is entirely analogous to that previously postulated for the photoexcited states sensitized by Hg(3P1) atoms but the rate constants for intersystem crossing and molecular decomposition are drastically decreased as a result of the smaller amount of energy available for the excitation.

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