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).

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.

Formylmethylene: The Triplet Ground State and the Lowest Singlet State

2013 ◽  
Vol 117 (10) ◽  
pp. 2152-2159 ◽  
Author(s):  
Jun Guan ◽  
Katherine R. Randall ◽  
Henry F. Schaefer ◽  
Huidong Li
Keyword(s):  
Ground State ◽  
Singlet State ◽  
Triplet Ground State

scholarly journals Triplet State Baird-Aromaticity in Macrocycles: Scope, Limitations and Complications

2020 ◽  
Author(s):  
Rabia Ayub ◽  
Ouissam El Bakouri ◽  
Joshua R. Smith ◽  
Kjell Jorner ◽  
Henrik Ottosson
Keyword(s):  
Triplet State ◽  
Ground State ◽  
Single Point ◽  
Closed Shell ◽  
The Other ◽  
Macrocyclic Compounds ◽  
Expanded Porphyrins ◽  
Diradical Character ◽  
Cyclic Oligomers ◽  
Electronic Ground

<p>The aromaticity of cyclic 4<i>n</i>p-electron molecules in their first pp* triplet state (T<sub>1</sub>), labelled Baird-aromaticity, has gained growing attention in the last decade. Here we explore computationally the limitations of T<sub>1</sub> state Baird-aromaticity in macrocyclic compounds, <b>[<i>n</i>]CM</b>’s, which are cyclic oligomers of four different monocycles (M = <i>para</i>-phenylene (PP), 2,5-linked furan (FU), 1,4-linked cyclohexa-1,3-diene (CHD), and 1,4-linked cyclopentadiene (CPD)). We strive for conclusions that are general for various DFT functionals, although for macrocycles with up to 20 p-electrons in their main conjugation paths we find that for their T<sub>1</sub> states single-point energies at both canonical UCCSD(T) and approximative DLPNO-UCCSD(T) levels are lowest when based on UB3LYP over UM06-2X and UCAM-B3LYP geometries. This finding is in contrast to what has earlier been observed for the electronic ground state of expanded porphyrins. Yet, irrespective of functional, macrocycles with 2,5-linked furans (<b>[<i>n</i>]CFU</b>’s) retain Baird-aromaticity until larger <i>n</i> than those composed of the other three monocycles. Also, when based on geometric, electronic and energetic aspects of aromaticity, a <b><sup>3</sup>[<i>n</i>]CFU</b> with a specific <i>n</i> is more strongly Baird-aromatic than the analogous <b><sup>3</sup>[<i>n</i>]CPP</b> while the magnetic indices tell the opposite. To construct large T<sub>1</sub> state Baird-aromatic <b>[<i>n</i>]CM</b>’s the design should be such that the T<sub>1</sub> state Baird-aromaticity of the macrocyclic perimeter dominates over a situation with local closed-shell Hückel-aromaticity of one or a few monocycles and semi-localized triplet diradical character. Monomers with lower Hückel-aromaticity in S<sub>0</sub> than benzene (<i>e.g.</i>, furan) that do not impose steric congestion are preferred. Structural confinement imposed by, <i>e.g.</i>, methylene bridges is also an approach to larger Baird-aromatic macrocycles. Finally, by using the Zilberg-Haas description of T<sub>1</sub> state aromaticity we reveal the analogy to the Hückel-aromaticity of the corresponding closed-shell dications, yet, observe stronger Hückel-aromaticity in the macrocyclic dications than Baird-aromaticity in the T<sub>1</sub> states of the neutral macrocycles. </p>

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.

Activation energy barrier for intersystem crossing in platinum phthalocyanine

1976 ◽  
Vol 54 (6) ◽  
pp. 633-637 ◽  
Author(s):  
Tzer-Hsiang Huang ◽  
Klaus E. Rieckhoff ◽  
Eva-Maria Voigt
Keyword(s):  
Triplet State ◽  
Ground State ◽  
Energy Barrier ◽  
Singlet State ◽  
Quantum Yields ◽  
Intersystem Crossing ◽  
Singlet Ground State ◽  
Activation Energy Barrier ◽  
Excited Singlet ◽  
Platinum Phthalocyanine

Phosphorescence quantum yields and lifetimes of platinum phthalocyanine in α-chloronaphthalene solution are reported for temperatures from 1.3 K to 300 K. Activation energies of intersystem crossing are deduced and found to be Ea = 17 ± 3 cm−1 for crossing from the first excited singlet state to the lowest lying triplet state and Eap = 8 ± 1 cm−1 for crossing from the lowest lying triplet state to the singlet ground state.

scholarly journals Strategies for Computer-Aided Discovery of Novel Open-Shell Polymers

2021 ◽  
Author(s):  
Omri Abarbanel ◽  
Julisa Rozon ◽  
Geoffrey Hutchison
Keyword(s):  
Ground State ◽  
Conjugated Polymer ◽  
Density Functional ◽  
Singlet State ◽  
Density Functional Theory Calculations ◽  
Open Shell ◽  
Singlet Ground State ◽  
Functional Theory ◽  
Triplet Ground State ◽  
Homo Lumo

Organic π-conjugated polymers with a triplet ground state have been the focus of recent research for their interesting and unique electronic properties, arising from the presence of the two unpaired electrons. These polymers are usually built from alternating electron-donating and electron-accepting monomer pairs which lower the HOMO-LUMO gap and yield a triplet state instead of the typical singlet ground state. In this paper we use density functional theory calculations to explore the design rules that govern the creation of a ground state triplet conjugated polymer, and find that a small HOMO-LUMO gap in the singlet state is the best predictor for the existence of a triplet ground state, compared to previous use of pro-quinoidal character. This work can accelerate the discovery of new stable triplet materials by reducing the computa- tional resources needed for electronic-state calculations and the number of potential candidates for synthesis.

scholarly journals Triplet State Baird-Aromaticity in Macrocycles: Scope, Limitations and Complications

2020 ◽  
Author(s):  
Rabia Ayub ◽  
Ouissam El Bakouri ◽  
Joshua R. Smith ◽  
Kjell Jorner ◽  
Henrik Ottosson
Keyword(s):  
Triplet State ◽  
Ground State ◽  
Single Point ◽  
Closed Shell ◽  
The Other ◽  
Macrocyclic Compounds ◽  
Expanded Porphyrins ◽  
Diradical Character ◽  
Cyclic Oligomers ◽  
Electronic Ground

<p>The aromaticity of cyclic 4<i>n</i>p-electron molecules in their first pp* triplet state (T<sub>1</sub>), labelled Baird-aromaticity, has gained growing attention in the last decade. Here we explore computationally the limitations of T<sub>1</sub> state Baird-aromaticity in macrocyclic compounds, <b>[<i>n</i>]CM</b>’s, which are cyclic oligomers of four different monocycles (M = <i>para</i>-phenylene (PP), 2,5-linked furan (FU), 1,4-linked cyclohexa-1,3-diene (CHD), and 1,4-linked cyclopentadiene (CPD)). We strive for conclusions that are general for various DFT functionals, although for macrocycles with up to 20 p-electrons in their main conjugation paths we find that for their T<sub>1</sub> states single-point energies at both canonical UCCSD(T) and approximative DLPNO-UCCSD(T) levels are lowest when based on UB3LYP over UM06-2X and UCAM-B3LYP geometries. This finding is in contrast to what has earlier been observed for the electronic ground state of expanded porphyrins. Yet, irrespective of functional, macrocycles with 2,5-linked furans (<b>[<i>n</i>]CFU</b>’s) retain Baird-aromaticity until larger <i>n</i> than those composed of the other three monocycles. Also, when based on geometric, electronic and energetic aspects of aromaticity, a <b><sup>3</sup>[<i>n</i>]CFU</b> with a specific <i>n</i> is more strongly Baird-aromatic than the analogous <b><sup>3</sup>[<i>n</i>]CPP</b> while the magnetic indices tell the opposite. To construct large T<sub>1</sub> state Baird-aromatic <b>[<i>n</i>]CM</b>’s the design should be such that the T<sub>1</sub> state Baird-aromaticity of the macrocyclic perimeter dominates over a situation with local closed-shell Hückel-aromaticity of one or a few monocycles and semi-localized triplet diradical character. Monomers with lower Hückel-aromaticity in S<sub>0</sub> than benzene (<i>e.g.</i>, furan) that do not impose steric congestion are preferred. Structural confinement imposed by, <i>e.g.</i>, methylene bridges is also an approach to larger Baird-aromatic macrocycles. Finally, by using the Zilberg-Haas description of T<sub>1</sub> state aromaticity we reveal the analogy to the Hückel-aromaticity of the corresponding closed-shell dications, yet, observe stronger Hückel-aromaticity in the macrocyclic dications than Baird-aromaticity in the T<sub>1</sub> states of the neutral macrocycles. </p>

Reactivity of dioxygen and its activation for selective dioxygenation, mono-oxygenation, dehydrogenation, and auto-oxidation of organic substrates and metals (corrosion)

1992 ◽  
Author(s):  
Donald T. Sawyer ◽  
R. J. P. Williams
Keyword(s):  
Triplet State ◽  
Electronic State ◽  
Energy Flux ◽  
Ground State ◽  
Oxidative Metabolism ◽  
Singlet State ◽  
Direct Reaction ◽  
Organic Substrates ◽  
Reversible Binding ◽  
Radical Character

Ground-state dioxygen has two unpaired electrons (·O2·), which makes it a biradical with a triplet electronic state (see Table 3-1). Its radical character is limited because the H-OO· bond is weak [-ΔGBF/ 51 kcal (Chapter 3)], and the triplet state precludes direct reaction with singlet-state substrate molecules with saturated σ bonding. Perhaps the most important (but nonproductive) reaction chemistry for 3O2 is its reversible binding by the metalloproteins: hemoglobin, myoglobin, hemerythrin, and hemocyanin. Nature developed such systems to obviate the limited solubility of O2 in water (~1 mM at 1 atm O2), which restricts the energy flux from oxidative metabolism in aerobic organisms.

scholarly journals Triplet State Baird-Aromaticity in Macrocycles: Scope, Limitations and Complications

2020 ◽  
Author(s):  
Rabia Ayub ◽  
Ouissam El Bakouri ◽  
Joshua R. Smith ◽  
Kjell Jorner ◽  
Henrik Ottosson
Keyword(s):  
Triplet State ◽  
Ground State ◽  
Single Point ◽  
Closed Shell ◽  
The Other ◽  
Macrocyclic Compounds ◽  
Expanded Porphyrins ◽  
Diradical Character ◽  
Cyclic Oligomers ◽  
Electronic Ground

<p>The aromaticity of cyclic 4<i>n</i>p-electron molecules in their first pp* triplet state (T<sub>1</sub>), labelled Baird-aromaticity, has gained growing attention in the last decade. Here we explore computationally the limitations of T<sub>1</sub> state Baird-aromaticity in macrocyclic compounds, <b>[<i>n</i>]CM</b>’s, which are cyclic oligomers of four different monocycles (M = <i>para</i>-phenylene (PP), 2,5-linked furan (FU), 1,4-linked cyclohexa-1,3-diene (CHD), and 1,4-linked cyclopentadiene (CPD)). We strive for conclusions that are general for various DFT functionals, although for macrocycles with up to 20 p-electrons in their main conjugation paths we find that for their T<sub>1</sub> states single-point energies at both canonical UCCSD(T) and approximative DLPNO-UCCSD(T) levels are lowest when based on UB3LYP over UM06-2X and UCAM-B3LYP geometries. This finding is in contrast to what has earlier been observed for the electronic ground state of expanded porphyrins. Yet, irrespective of functional, macrocycles with 2,5-linked furans (<b>[<i>n</i>]CFU</b>’s) retain Baird-aromaticity until larger <i>n</i> than those composed of the other three monocycles. Also, when based on geometric, electronic and energetic aspects of aromaticity, a <b><sup>3</sup>[<i>n</i>]CFU</b> with a specific <i>n</i> is more strongly Baird-aromatic than the analogous <b><sup>3</sup>[<i>n</i>]CPP</b> while the magnetic indices tell the opposite. To construct large T<sub>1</sub> state Baird-aromatic <b>[<i>n</i>]CM</b>’s the design should be such that the T<sub>1</sub> state Baird-aromaticity of the macrocyclic perimeter dominates over a situation with local closed-shell Hückel-aromaticity of one or a few monocycles and semi-localized triplet diradical character. Monomers with lower Hückel-aromaticity in S<sub>0</sub> than benzene (<i>e.g.</i>, furan) that do not impose steric congestion are preferred. Structural confinement imposed by, <i>e.g.</i>, methylene bridges is also an approach to larger Baird-aromatic macrocycles. Finally, by using the Zilberg-Haas description of T<sub>1</sub> state aromaticity we reveal the analogy to the Hückel-aromaticity of the corresponding closed-shell dications, yet, observe stronger Hückel-aromaticity in the macrocyclic dications than Baird-aromaticity in the T<sub>1</sub> states of the neutral macrocycles. </p>

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