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.

Triplet-State Kinetics of 2,5 Diphenyloxazole (PPO)

1988 ◽  
Vol 42 (1) ◽  
pp. 27-31
Author(s):  
A. N. Dharamsi ◽  
Shawpin Jong
Keyword(s):  
Excited State ◽  
Triplet State ◽  
Absorption Spectra ◽  
Rate Constants ◽  
Intersystem Crossing ◽  
Time Resolved ◽  
Probe Technique ◽  
Pump And Probe ◽  
Kinetics Of ◽  
Triplet Absorption

Time-resolved excited-state triplet-triplet absorption spectra were measured for solutions of 2,5 diphenyloxazole (PPO) in various solvents, with the use of a pump and probe technique. The rate constants for intersystem crossing, triplet deactivation by oxygen, and triplet-triplet self-quenching are obtained. The latter two rate constants are substantially larger than the corresponding rate constants for 2-(1 naphthyl)-5-phenyloxazole-αNPO.

Intramolecular H-bond design for efficient orange–red thermally activated delayed fluorescence based on a rigid dibenzo[f,h]pyrido[2,3-b]quinoxaline acceptor

2020 ◽  
Vol 8 (44) ◽  
pp. 15728-15734
Author(s):  
Feng-Ming Xie ◽  
Xin-Yi Zeng ◽  
Jing-Xiong Zhou ◽  
Zhi-Dong An ◽  
Wenjun Wang ◽  
...  
Keyword(s):  
Excited State ◽  
Rate Constants ◽  
High Efficiency ◽  
Delayed Fluorescence ◽  
Intersystem Crossing ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Molecular Excited State

Tune the molecular excited state and rate constants of radiative intersystem crossing by constructing intramolecular H-bonds to achieve high-efficiency orange–red TADF-OLEDs.

scholarly journals Kinetic Prediction of Reverse Intersystem Crossing in Organic Donor–Acceptor Molecules

2020 ◽  
Author(s):  
Naoya Aizawa ◽  
Yu Harabuchi ◽  
Satoshi Maeda ◽  
Yong-Jin Pu
Keyword(s):  
Excited State ◽  
Rate Constants ◽  
Rational Design ◽  
Molecular Structures ◽  
Theoretical Expression ◽  
Substitution Effects ◽  
Intersystem Crossing ◽  
Predictive Tool ◽  
Spin Flip ◽  
Wide Range

Reverse intersystem crossing (RISC), the uphill spin-flip process from a triplet to a singlet excited state, plays a key role in a wide range of photochemical applications. Understanding and predicting the kinetics of such processes in vastly different molecular structures would facilitate the rational design of new materials. Here, we demonstrate a theoretical expression that successfully reproduces experimental RISC rate constants ranging over five orders of magnitude in twenty different molecules. We show that the spin flip occurs across the singlet–triplet crossing seam involving a higher-lying triplet excited state where the semi-classical Marcus parabola is no longer valid. The present model explains the counterintuitive substitution effects of bromine on the RISC rate constants of newly synthesized molecules, providing a predictive tool for material design.<br>

Experimental Evidence for the Existence of an Electronically Excited State of the Proposed Dihydrogen Radical Cation He-H-H-He+

2009 ◽  
Vol 15 (16) ◽  
pp. 4190-4194 ◽  
Author(s):  
Stefan Jaksch ◽  
Filipe Ferreira da Silva ◽  
Stephan Denifl ◽  
Olof Echt ◽  
Tilmann D. Märk ◽  
...  
Keyword(s):  
Excited State ◽  
Experimental Evidence ◽  
Radical Cation ◽  
Electronically Excited State ◽  
Electronically Excited

scholarly journals Kinetic Prediction of Reverse Intersystem Crossing in Organic Donor–Acceptor Molecules

2020 ◽  
Author(s):  
Naoya Aizawa ◽  
Yu Harabuchi ◽  
Satoshi Maeda ◽  
Yong-Jin Pu
Keyword(s):  
Excited State ◽  
Rate Constants ◽  
Rational Design ◽  
Molecular Structures ◽  
Theoretical Expression ◽  
Substitution Effects ◽  
Intersystem Crossing ◽  
Predictive Tool ◽  
Spin Flip ◽  
Wide Range

Reverse intersystem crossing (RISC), the uphill spin-flip process from a triplet to a singlet excited state, plays a key role in a wide range of photochemical applications. Understanding and predicting the kinetics of such processes in vastly different molecular structures would facilitate the rational design of new materials. Here, we demonstrate a theoretical expression that successfully reproduces experimental RISC rate constants ranging over five orders of magnitude in twenty different molecules. We show that the spin flip occurs across the singlet–triplet crossing seam involving a higher-lying triplet excited state where the semi-classical Marcus parabola is no longer valid. The present model explains the counterintuitive substitution effects of bromine on the RISC rate constants of newly synthesized molecules, providing a predictive tool for material design.<br>

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.

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

Electronically excited state structures and stabilities of organic small molecules: A DFT study of triphenylamine derivatives

2021 ◽  
pp. 111256
Author(s):  
Kun Gong ◽  
Jieqiong Yang ◽  
Thomas T. Testoff ◽  
Wei Li ◽  
Tianyang Wang ◽  
...  
Keyword(s):  
Excited State ◽  
Small Molecules ◽  
Dft Study ◽  
Electronically Excited State ◽  
Electronically Excited

scholarly journals Theoretical Electronic and Rovibrational Studies for Anions of Interest to the DIBs

2013 ◽  
Vol 9 (S297) ◽  
pp. 344-348 ◽  
Author(s):  
R. C. Fortenberry
Keyword(s):  
Excited State ◽  
Excited States ◽  
State Of The Art ◽  
Spectroscopic Constants ◽  
Coupled Cluster ◽  
Electronic Excitations ◽  
Electronically Excited States ◽  
Coupled Cluster Theory ◽  
Electronically Excited ◽  
Enolate Anion

AbstractThe dipole-bound excited state of the methylene nitrile anion (CH2CN−) has been suggested as a candidate carrier for a diffuse interstellar band (DIB) at 803.8 nm. Its corresponding radical has been detected in the interstellar medium (ISM), making the existence for the anion possible. This work applies state-of-the-art ab initio methods such as coupled cluster theory to reproduce accurately the electronic excitations for CH2CN− and the similar methylene enolate anion, CH2CHO−. This same approach has been employed to indicate that 19 other anions may possess electronically excited states, five of which are valence in nature. Concurrently, in order to assist in the detection of these anions in the ISM, work has also been directed towards predicting vibrational frequencies and spectroscopic constants for these anions through the use of quartic force fields (QFFs). Theoretical rovibrational work on anions has thus far included studies of CH2CN−, C3H−, and is currently ongoing for similar systems.

Luminescence Quenching of Rhodamines by Cyclooctatetraene

1987 ◽  
Vol 42 (9) ◽  
pp. 1009-1013 ◽  
Author(s):  
P. Targowski ◽  
B. Ziętek ◽  
A. Bączyński
Keyword(s):  
Rhodamine B ◽  
Rate Constants ◽  
Internal Conversion ◽  
Rhodamine 6G ◽  
Second Order ◽  
Luminescence Quenching ◽  
Intersystem Crossing ◽  
Order Rate ◽  
Quenching Process

Cyclooctatetraene (COT) as a quencher of fluorescence of a series of Rhodamine solutions was studied. The second order rate constants for the quenching process of Rhodamine 110, Rhodamine 19 pchl., Rhodamine 6G pchl., Rhodamine 6G, Tetramethylrhodamine, Rhodamine B and Rhodamine 3B pchl. are given. It was found that COT enhances rather intersystem crossing than internal conversion.

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