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.

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 Improving photosensitization for photochemical CO2-to-CO conversion

2020 ◽  
Vol 7 (9) ◽  
pp. 1459-1467
Author(s):  
Ping Wang ◽  
Ru Dong ◽  
Song Guo ◽  
Jianzhang Zhao ◽  
Zhi-Ming Zhang ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Driving Force ◽  
Cobalt Catalyst ◽  
Co2 Reduction ◽  
Excited State Lifetime ◽  
Turnover Number ◽  
Co Conversion ◽  
First Time ◽  
Insight Into

Abstract Inspired by nature, improving photosensitization represents a vital direction for the development of artificial photosynthesis. The sensitization ability of photosensitizers (PSs) reflects in their electron-transfer ability, which highly depends on their excited-state lifetime and redox potential. Herein, for the first time, we put forward a facile strategy to improve sensitizing ability via finely tuning the excited state of Ru(II)-PSs (Ru-1–Ru-4) for efficient CO2 reduction. Remarkably, [Ru(Phen)2(3-pyrenylPhen)]2+ (Ru-3) exhibits the best sensitizing ability among Ru-1–Ru-4, over 17 times higher than that of typical Ru(Phen)32+. It can efficiently sensitize a dinuclear cobalt catalyst for CO2-to-CO conversion with a maximum turnover number of 66 480. Systematic investigations demonstrate that its long-lived excited state and suitable redox driving force greatly contributed to this superior sensitizing ability. This work provides a new insight into dramatically boosting photocatalytic CO2 reduction via improving photosensitization.

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 photochemical reaction of tris(ethylenediamine)cobalt(III) ion with ferrocyanide

1981 ◽  
Vol 59 (4) ◽  
pp. 647-651 ◽  
Author(s):  
Cooper H. Langford ◽  
Roger L. P. Sasseville
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Excited States ◽  
Photochemical Reaction ◽  
Ion Pairs ◽  
Ligand Field ◽  
Excited State Lifetime ◽  
Photochemical Formation ◽  
Reaction Proceeds ◽  
Reactive Excited State

The photochemical formation of [Cl(en)2Co—N≡C—Fe(CN)5]2− from Co(en)33+ and Fe(CN)64− is explored. Earlier evidence established that the reaction proceeds via electron transfer. Ligand field Co(III) excited states are clearly indicated to be effective. There is evidence that free Fe(CN)64− can scavenge these excited states or their successors arising in ion pairs with Fe(CN)64−. This suggests that the reactive excited state lifetime is at least comparable to the rate of diffusional encounters. However, racemization does not accompany reaction if (+)589Co(en)33+ is the reactant. Wavelength studies indicate approximate wavelength independence as far as 647.1 nm. These results are in contrast with the behaviour of photosubstitution yields for Co(III) amines.

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

Electron transfer sensitized photolysis of 'onium salts

1988 ◽  
Vol 66 (2) ◽  
pp. 319-324 ◽  
Author(s):  
R. J. DeVoe ◽  
M. R. V. Sahyun ◽  
Einhard Schmidt ◽  
N. Serpone ◽  
D. K. Sharma
Keyword(s):  
Electron Transfer ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Quantitative Model ◽  
Intersystem Crossing ◽  
Single Electron Transfer ◽  
Onium Salts ◽  
Encounter Complex ◽  
Back Electron Transfer

We have studied the anthracene-sensitized photolyses of both diphenyliodonium and triphenylsulphonium salts in solution using both steady-state and laser flash photolysis techniques. Photoproducts, namely, phenylated anthracenes along with iodobenzene or diphenylsulphide, respectively, are obtained from both salts with quantum efficiencies of ca. 0.1 at 375 nm. We infer the intermediacy of diphenyliodo and triphenylsulphur radicals formed by single electron transfer from the singlet-excited anthracene. We have developed a quantitative model of this chemistry, and identify the principal sources of inefficiency as back electron transfer, which occurs at nearly the theoretically limiting rate, intersystem crossing from the initially formed sensitizer–'onium salt encounter complex, and in-cage radical recombination.

Sign in / Sign up

Export Citation Format

Share Document