scholarly journals Formation of a stable biradical triplet state cation versus a closed shell singlet state cation by oxidation of adducts of 3,6-dimethoxycarbazole and polychlorotriphenylmethyl radicals

2019 ◽  
Vol 21 (36) ◽  
pp. 20225-20231
Author(s):  
Paola Ballesteros ◽  
Alba Cuadrado ◽  
Alejandra Gilabert ◽  
Lluís Fajarí ◽  
Ignasi Sirés ◽  
...  
Keyword(s):  
Triplet State ◽  
Singlet State ◽  
Closed Shell ◽  
Methyl Radical

The oxidation of the dimethoxicarbazole adduct of the tris(2,3,5,6-tetrachlorophenyl)methyl radical (DTM) involves ionization of one electron from the HOMO rather than from the SOMO, to generate a triplet state.

Sulfamoyl nitrenes: singlet or triplet ground state?

2018 ◽  
Vol 54 (48) ◽  
pp. 6136-6139 ◽  
Author(s):  
Yan Lu ◽  
Hongmin Li ◽  
Manabu Abe ◽  
Didier Bégué ◽  
Huabin Wan ◽  
...  
Keyword(s):  
Triplet State ◽  
Ground State ◽  
Singlet State ◽  
Minimum Energy ◽  
Closed Shell ◽  
Low Energy ◽  
Energy Minimum ◽  
Triplet Ground State ◽  
Crossing Point

Two prototypical sulfamoyl nitrenes R2NS(O)2–N (R = H and Me) in the triplet state were generated via the closed-shell singlet state by passing a low-energy minimum energy crossing point (MECP).

Photolysis of ketene. I

1968 ◽  
Vol 46 (14) ◽  
pp. 2353-2360 ◽  
Author(s):  
A. N. Strachan ◽  
D. E. Thornton
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Triplet State ◽  
Singlet State ◽  
Inert Gases ◽  
Inert Gas ◽  
Excited Singlet State ◽  
Intersystem Crossing ◽  
Excited Singlet ◽  
Increasing Temperature

Ketene has been photolyzed at 3660 and 3130 Å both alone and in the presence of the inert gases C4F8 and SF6. The quantum yield of carbon monoxide has been determined at both wavelengths as a function of pressure and temperature. At 3660 Å the quantum yield decreases with increasing pressure but increases with increasing temperature. At 3130 Å the quantum yield with ketene alone remains 2.0 at both 37 and 100 °C at pressures up to 250 mm. At higher pressures of ketene or with added inert gas the quantum yield decreases with increasing pressure. The results are interpreted in terms of a mechanism in which intersystem crossing from the excited singlet state to the triplet state occurs at both wavelengths, and collisional deactivation of the excited singlet state by ketene is single stage at 3660 Å but multistage at 3130 Å.

scholarly journals Geometries and Electronic States of Divacancy Defect in Finite-Size Hexagonal Graphene Flakes

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Lili Liu ◽  
Shimou Chen
Keyword(s):  
Ground State ◽  
First Principles ◽  
Density Functional ◽  
Singlet State ◽  
Tight Binding ◽  
Finite Size ◽  
Electronic States ◽  
Closed Shell ◽  
Graphene Flakes ◽  
Self Consistent

The geometries and electronic properties of divacancies with two kinds of structures were investigated by the first-principles (U) B3LYP/STO-3G and self-consistent-charge density-functional tight-binding (SCC-DFTB) method. Different from the reported understanding of these properties of divacancy in graphene and carbon nanotubes, it was found that the ground state of the divacancy with 585 configurations is closed shell singlet state and much more stable than the 555777 configurations in the smaller graphene flakes, which is preferred to triplet state. But when the sizes of the graphene become larger, the 555777 defects will be more stable. In addition, the spin density properties of the both configurations are studied in this paper.

Thermochemical parameters for organic radicals and radical ions. Part 3. The relationship between bond dissociation enthalpy and radical stability in alkyl systems

1984 ◽  
Vol 62 (9) ◽  
pp. 1850-1859 ◽  
Author(s):  
A. Martin de P. Nicholas ◽  
Donald R. Arnold
Keyword(s):  
Closed Shell ◽  
Bond Dissociation Enthalpy ◽  
Methyl Radical ◽  
Bond Dissociation ◽  
Secondary Bonds ◽  
Dissociation Enthalpy ◽  
Relative Stabilization ◽  
Stabilization Energies ◽  
Thermochemical Parameters ◽  
The Relationship

The relationship between radical stability and bond dissociation enthalpy (BDH) is reexamined. It is shown that relative stabilization energies of radicals are not equal to relative BDH values. Net stabilization energies of radicals, SE0[R•, RX] are defined relative to the R components of closed shell species RX (R(RX)). These components are chosen such that they contain the same (or, approximately the same) net charge as that of the radical (R•). The following results, relative to R = C2H5, were obtained: R•, SE0[R•, RX](kJ mol−1) for X = R (i.e., the dimer RR), CH3, and H; CH3•, 23, 32, 37; n-C3H7•, −2, −2, −3; i-C3H7•, −9, −14, −19; t-C4H9•, −25, −32, −38. These results show that the methyl radical is more destabilized and the n-propyl-, i-propyl-, and tert-butyl radicals are more stabilized than is predicted from the corresponding relative BDH (R—X) values. The intrinsic C—H bond strengths of chosen alkanes are considered. Relative to the C—H bond in ethane, the bond in methane is found to be weaker by 8.12 kJ mol−1 and the primary and secondary bonds in propane and the tertiary bond in methyl propane are stronger by 2.56, 7.98, and 17.12 kJ mol−1 respectively.

Photoreactions of Simple Halonaphthalenes in Solution

1975 ◽  
Vol 53 (5) ◽  
pp. 688-693 ◽  
Author(s):  
Luis Octavio Ruzo ◽  
Nigel J. Bunce ◽  
S. Safe
Keyword(s):  
Electron Transfer ◽  
Triplet State ◽  
Singlet State ◽  
Abnormal Behavior ◽  
Quantum Yields ◽  
Transfer Processes ◽  
Electron Transfer Processes

The photolysis products and reaction quantum yields from a number of simple halonaphthalenes have been determined. Fluoronaphthalenes react from a singlet state to yield substitution products in nucleophilic solvents. Chloronaphthalenes and 1-bromonaphthalene afford mainly radical products (naphthalene and binaphthyls) through a triplet state, though some photonucleophilic substitution occurs with chloronaphthalene. Attempts at quenching lead to abnormal behavior, in that enhanced quantum yields for reaction are found with several potential triplet quenchers. Electron transfer processes are proposed to rationalize the observed products.

Tuning Ground States of Bis(triarylamine) Dications: From a Closed-Shell Singlet to a Diradicaloid with an Excited Triplet State

2014 ◽  
Vol 126 (11) ◽  
pp. 2901-2905 ◽  
Author(s):  
Yuanting Su ◽  
Xingyong Wang ◽  
Xin Zheng ◽  
Zaichao Zhang ◽  
You Song ◽  
...  
Keyword(s):  
Triplet State ◽  
Ground States ◽  
Closed Shell ◽  
Excited Triplet State ◽  
Excited Triplet

Molecular orbital studies of the singlet and triplet states of formylmethylene conformers

1991 ◽  
Vol 69 (11) ◽  
pp. 1630-1635 ◽  
Author(s):  
Ratnakar K. Gosavi ◽  
Manuel Torres ◽  
Otto P. Strausz
Keyword(s):  
Singlet State ◽  
Closed Shell ◽  
Basis Set ◽  
Planar Geometry ◽  
Present Calculation ◽  
Triplet States ◽  
Excited Singlet ◽  
Singlet And Triplet States ◽  
Ci Calculations ◽  
Single Configuration

The energies and geometries of the low-lying electronic states of formylmethylene have been calculated at the SCF and CI levels using 6-31G** basis set. In agreement with previous reports and accumulated experimental observations, the ground state is the carbenoid triplet with a planar geometry. Also, in agreement with all previous single configuration SCF and CI calculations, the lowest excited singlet state is computed to be the nonplanar closed shell carbenoid structure. In contrast, accumulated experimental evidence along with previously reported MC–SCF results require this state to be planar. The present calculation predicts the existence of a (σ–σ) 1,3-diradical 1A′ state, which appears to be identical to the MC–SCF lowest singlet state, but this state lies some 11 kcal/mol above the closed shell carbenoid 1A state. Apparently, single configuration SCF methods are inadequate for the correct description of the electronic manifold of formylmethylene. Key words: formylmethylene, singlet and triplet states, ab initio MO calculations, conformers, molecular structure.

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