Influence of Chain Length and Derivatization on the Lowest Singlet and Triplet States and Intersystem Crossing in Oligothiophenes

1996 ◽  
Vol 118 (27) ◽  
pp. 6453-6461 ◽  
Author(s):  
D. Beljonne ◽  
J. Cornil ◽  
R. H. Friend ◽  
R. A. J. Janssen ◽  
J. L. Brédas
Keyword(s):  
Chain Length ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Singlet And Triplet States

scholarly journals The role of Duschinsky rotation in intersystem crossing: A case study of uracil

2011 ◽  
Vol 76 (12) ◽  
pp. 1649-1660 ◽  
Author(s):  
Mihajlo Etinski
Keyword(s):  
Correlation Function ◽  
Normal Modes ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Cumulant Expansion ◽  
Time Approximation ◽  
Energy Gaps ◽  
Singlet And Triplet States ◽  
Quantitative Results ◽  
Short Time

The intersystem crossing rate for the transition between the lowest excited singlet and triplet electronic states of uracil was studied by means of ab initio methods. The rate was evaluated using the timedependent approach based on the correlation function and its two approximations: the second-order cumulant expansion and the short-time approximation. The normal modes of the singlet and triplet states are related by the Duschinsky transformation, i.e., by rotation and translation. It was found that for singlet-triplet adiabatic energy gaps below 6000 cm-1, the inclusion of the Duschinsky rotation is necessary for quantitative results. Above energy gaps of 6000 cm-1, the rates obtained with and without the Duschinsky rotation are similar. The cumulant expansion approximates well the correlation function. The short-time approximation, although crude, can be used as the first estimate of the rate.

The mechanism of the gas phase photolysis of acetone

1966 ◽  
Vol 290 (1423) ◽  
pp. 563-582 ◽  
Keyword(s):  
Gas Phase ◽  
Order Rate Constant ◽  
Electronic Energy ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Excited Singlet ◽  
First Order ◽  
Electronic Energy Transfer ◽  
Vibrational Levels ◽  
Singlet And Triplet States

A mechanism for the photolysis of acetone has been derived from experimental data including studies on the photosensitized isomerization of olefines. Dissociation into methyl and acetyl radicals occurs from both the first excited singlet and triplet states; the rate constants for excitation by light of 3130 Å wavelength are 2.5 x 10 16 exp ( —16900/ RT ) and 2.5 x 10 10 exp ( — 6400/ RT ) 1. mole -1 s -1 respectively. At low intensities of absorption, decomposition of acetyl radicals predominates over radical-radical interactions. The triplet state is extensively populated at moderate temperatures, the yield at 48 °C being 0.98. The low phosphorescence efficiency of acetone can be ascribed to intersystem crossing to the ground state for which the first order rate constant is 1.25 x 10 5 s -1 . The isomerization data requires the recognition of at least two vibrational levels of the acetone triplet, the rate of electronic energy transfer depending upon the excess energy possessed by the donor

scholarly journals Photophysical Properties of Nitrated and Halogenated Phosphorus Tritolylcorrole Complexes: Insights from Theory

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2779 ◽  
Author(s):  
Marta Alberto ◽  
Bruna De Simone ◽  
Gloria Mazzone ◽  
Nino Russo ◽  
Marirosa Toscano
Keyword(s):  
Excited States ◽  
Density Functional ◽  
Energy Gap ◽  
Photophysical Properties ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Excited Singlet ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Singlet And Triplet States

The photophysical properties of a series of nitrated and halogenated phosphorus tritolylcorrole complexes were studied in dichloromethane solvent by using the density functional theory. Particular emphasis was given to the absorption spectra, the energy gap between the excited singlet and triplet states, and the magnitude of the spin-orbit couplings for a series of possible intersystem crossing channels between those excited states. The proposed study provides a better description of the photophysical properties of these systems while giving insights into their possible use as photosensitizers in photodynamic therapy.

CNDO/S CI calculation of spin-orbit coupling and intersystem crossing in photochemical biradical formation reaction

1981 ◽  
Vol 46 (6) ◽  
pp. 1318-1323 ◽  
Author(s):  
Boris F. Minaev ◽  
David M. Kižner
Keyword(s):  
Nuclear Polarization ◽  
Orbit Coupling ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Formation Reaction ◽  
Chemically Induced ◽  
Singlet And Triplet States ◽  
Ci Calculation

The CNDO/S CI method has been employed to calculate potential curves for singlet and triplet states along reaction path for photolysis of cyclopentanone (dissociation of the C-C bond and biradical formation). Spin-orbit coupling between these two states and the probability of intersystem crossing (ISC) in Landau-Zener approximation were calculated. This probability has proved enough to compete with nuclear spin induced ISC process. In this way some peculiarities of chemically induced dynamic nuclear polarization in formation of products via biradicals can be qualitatively understood.

scholarly journals Unexpectedly Long Lifetime of the Excited State of Benzothiadiazole Derivative and Its Adducts with Lewis Acids

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2030
Author(s):  
Taisiya S. Sukhikh ◽  
Radmir M. Khisamov ◽  
Sergey N. Konchenko
Keyword(s):  
Lewis Acids ◽  
Bromine Atom ◽  
Heavy Atom ◽  
Intersystem Crossing ◽  
Triplet States ◽  
X Ray Diffraction ◽  
X Ray ◽  
Singlet And Triplet States ◽  
Long Lifetime ◽  
Atom Effect

We report a study of photoluminescent properties of 4-bromo-7-(3-pyridylamino)-2,1,3-benzothiadiazole (Py-btd) and its novel Lewis adducts: (PyH-btd)2(ZnCl4) and [Cu2Cl2(Py-btd)2{PPO}2]·2C7H8 (PPO = tetraphenyldiphosphine monoxide), whose crystal structure was determined by X-ray diffraction analysis. Py-btd exhibits a lifetime of 9 microseconds indicating its phosphorescent nature, which is rare for purely organic compounds. This phenomenon arises from the heavy atom effect: the presence of a bromine atom in Py-btd promotes mixing of the singlet and triplet states to allow efficient singlet-to-triplet intersystem crossing. The Lewis adducts also feature a microsecond lifetime while emitting in a higher energy range than free Py-btd, which opens up the possibility to color-tune luminescence of benzothiadiazole derivatives.

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