scholarly journals Switching between mono- and doubly-reduced odd alternant hydrocarbon: Designing redox catalyst

2021 ◽  
Author(s):  
Swadhin K Mandal ◽  
Jasimuddin Ahmed ◽  
Paramita Datta ◽  
Arpan Das ◽  
Stephy Jomy
Keyword(s):  
Molecular Orbital ◽  
Redox States ◽  
Redox Catalyst ◽  
Alternant Hydrocarbon

Since the early Hückel molecular orbital (HMO) calculations in 1950, it is well known that the odd alternant hydrocarbon (OAH), phenalenyl (PLY) system can exist in three redox states: closed...

Valence-Bond and Hückel Molecular Orbital Diradicals—Alternant versus Nonalternant Effects

2003 ◽  
Vol 56 (12) ◽  
pp. 1225 ◽  
Author(s):  
Jerry Ray Dias
Keyword(s):  
Molecular Orbital ◽  
Valence Bond ◽  
Polar Species ◽  
Alternant Hydrocarbon

Two distinct classes of diradicals are examined and compared. Valence-bond diradicals are topologically enforced, whereas Hückel molecular orbital diradicals can undergo skeletal distortions and transform to a nonradical form and tend to gain or lose electrons to form stable polyions. Alternant hydrocarbon diradicals are nonpolar species and nonalternant hydrocarbon diradicals tend to be polar species and less prevalent.

Oxophenalenoxyl: Novel stable neutral radicals with a unique spin-delocalized nature depending on topological symmetries and redox states

2008 ◽  
Vol 80 (3) ◽  
pp. 507-517 ◽  
Author(s):  
Yasushi Morita ◽  
Shinsuke Nishida ◽  
Junya Kawai ◽  
Takeji Takui ◽  
Kazuhiro Nakasuji
Keyword(s):  
Spin Density ◽  
Open Shell ◽  
Two Stage ◽  
Neutral Radical ◽  
Redox States ◽  
Density Distributions ◽  
Alternant Hydrocarbon ◽  
Redox Ability ◽  
Unique Spin ◽  
Oxygen Atoms

Stable organic open-shell systems have attracted much attention in the field of molecule-based magnetism. We have been exploring novel stable neutral radicals based on a phenalenyl system known as an odd-alternant hydrocarbon π-radical with a highly spin-delocalized nature. Recently, we have designed and synthesized novel oxophenalenoxyl neutral radical systems possessing two oxygen atoms on the phenalenyl skeleton. These systems are unique in comprising some topological isomers depending on the positions of oxygen substituents on the phenalenyl skeleton. The isomers exhibit different topological symmetries of spin density distributions (spin topological symmetry control). In addition, two-stage one-electron reductions of these systems give the corresponding radical dianions, which show remarkably different topological symmetries of a spin-delocalized nature from those of the neutral radical systems (redox-based spin diversity). In this paper, we discuss the unique spin-delocalized nature of 3-, 4-, and 6-oxophenalenoxyl systems in view of the topological symmetry and redox ability, emphasizing the results from the radical dianion of 4-oxophenalenoxyl system from both experimental and theoretical sides.

Ultraviolet spectra of non-alternant hydrocarbons: The significance of non-neighbour resonance integrals and of configuration-interaction

1968 ◽  
Vol 21 (8) ◽  
pp. 1939 ◽  
Author(s):  
RD Brown ◽  
FR Burden ◽  
GR Williams
Keyword(s):  
Molecular Orbital ◽  
Excited States ◽  
Configuration Interaction ◽  
Molecular Orbital Calculation ◽  
Alternative Methods ◽  
General Level ◽  
Nearest Neighbours ◽  
Alternant Hydrocarbon ◽  
Alternant Hydrocarbons ◽  
Method Of Evaluation

A study has been made of the way in which the calculated positions of excited states of non-alternant hydrocarbons are affected by (a) including all resonance integrals rather than just those for nearest neighbours (b) including configuration-interaction. The VESCF molecular-orbital technique, with two alternative methods for deriving basic integrals, was employed. Predicted positions of excited states are found to be sometimes appreciably altered when all resonance integrals are included, and are somewhat dependent upon the method of evaluation of basic integrals. We conclude that one should be cautious in interpreting U.V. spectra from an isolated molecular-orbital calculation on a non-alternant hydrocarbon. The study of the effect of configuration-interaction for the excited states of fulvene and dimethylenecyclobutene yields results analogous to those found by Koutecky and co-workers for benzene. The predicted relative positions of some excited states are altered when doubly excited configurations are included, but the general level of energies predicted for lower excited states when only singly excited configurations are used is probably close to the result that would be found when up to triply excited configurations are included.

Interactions between Methylene Blue and Pullulan According to Molecular Orbital Calculations

2020 ◽  
Vol 140 (11) ◽  
pp. 529-533
Author(s):  
Pasika Temeepresertkij ◽  
Saranya Yenchit ◽  
Michio Iwaoka ◽  
Satoru Iwamori
Keyword(s):  
Methylene Blue ◽  
Molecular Orbital ◽  
Molecular Orbital Calculations

Parallel Fock Matrix Construction Algorithm for Molecular Orbital Calculation Specific Computer

2006 ◽  
Vol 5 (1) ◽  
pp. 179-188
Author(s):  
Hiroaki UMEDA ◽  
Yuichi INADOMI ◽  
Hiroaki HONDA ◽  
Umpei NAGASHIMA
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbital Calculation ◽  
Construction Algorithm ◽  
Matrix Construction

Resolving the Quadruple Bonding Conundrum in C2 Using Insights Derived from Excited State Potential Energy Surfaces: A Molecular Orbital Perspective

2019 ◽  
Author(s):  
Ishita Bhattacharjee ◽  
Debashree Ghosh ◽  
Ankan Paul
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Molecular Orbital ◽  
High Spin ◽  
Potential Energy Surfaces ◽  
Valence Bond ◽  
Deep Minimum ◽  
State Potential ◽  
Energy Surfaces ◽  
Mo Theory

The question of quadruple bonding in C<sub>2</sub> has emerged as a hot button issue, with opinions sharply divided between the practitioners of Valence Bond (VB) and Molecular Orbital (MO) theory. Here, we have systematically studied the Potential Energy Curves (PECs) of low lying high spin sigma states of C<sub>2</sub>, N<sub>2</sub> and Be<sub>2</sub> and HC≡CH using several MO based techniques such as CASSCF, RASSCF and MRCI. The analyses of the PECs for the<sup> 2S+1</sup>Σ<sub>g/u</sub> (with 2S+1=1,3,5,7,9) states of C<sub>2</sub> and comparisons with those of relevant dimers and the respective wavefunctions were conducted. We contend that unlike in the case of N<sub>2</sub> and HC≡CH, the presence of a deep minimum in the <sup>7</sup>Σ state of C<sub>2</sub> and CN<sup>+</sup> suggest a latent quadruple bonding nature in these two dimers. Hence, we have struck a reconciliatory note between the MO and VB approaches. The evidence provided by us can be experimentally verified, thus providing the window so that the narrative can move beyond theoretical conjectures.

Radical Enzymes Control the Chemistry of Their Highly Reactive Intermediates Using the Quantum Coulombic Effect

2020 ◽  
Author(s):  
Hossein Khalilian ◽  
Gino A. DiLabio
Keyword(s):  
Hydrogen Bonding ◽  
Molecular Orbital ◽  
Reactive Intermediates ◽  
Hydrogen Bonding Interaction ◽  
Orbital Ordering ◽  
Dynamic Nature ◽  
Radical Intermediate ◽  
Highest Occupied Molecular Orbital ◽  
Bonding Interaction ◽  
Close Proximity

Here, we report an exquisite strategy that the B12 enzymes exploit to manipulate the reactivity of their radical intermediate (Adenosyl radical). Based on the quantum-mechanic calculations, these enzymes utilize a little known long-ranged through space quantum Coulombic effect (QCE). The QCE causes the radical to acquire an electronic structure that contradicts the Aufbau Principle: The singly-occupied molecular orbital (SOMO) is no longer the highest-occupied molecular orbital (HOMO) and the radical is unable to react with neighbouring substrates. The dynamic nature of the enzyme and its structure is expected to be such that the reactivity of the radical is not restored until it is moved into close proximity of the target substrate. We found that the hydrogen bonding interaction between the nearby conserved glutamate residue and the ribose ring of Adenosyl radical plays a crucial role in manipulating the orbital ordering

Radical Enzymes Control the Chemistry of Their Highly Reactive Intermediates Using the Quantum Coulombic Effect

2020 ◽  
Author(s):  
Hossein Khalilian ◽  
Gino A. DiLabio
Keyword(s):  
Hydrogen Bonding ◽  
Molecular Orbital ◽  
Reactive Intermediates ◽  
Hydrogen Bonding Interaction ◽  
Orbital Ordering ◽  
Dynamic Nature ◽  
Radical Intermediate ◽  
Highest Occupied Molecular Orbital ◽  
Bonding Interaction ◽  
Close Proximity

Here, we report an exquisite strategy that the B12 enzymes exploit to manipulate the reactivity of their radical intermediate (Adenosyl radical). Based on the quantum-mechanic calculations, these enzymes utilize a little known long-ranged through space quantum Coulombic effect (QCE). The QCE causes the radical to acquire an electronic structure that contradicts the Aufbau Principle: The singly-occupied molecular orbital (SOMO) is no longer the highest-occupied molecular orbital (HOMO) and the radical is unable to react with neighbouring substrates. The dynamic nature of the enzyme and its structure is expected to be such that the reactivity of the radical is not restored until it is moved into close proximity of the target substrate. We found that the hydrogen bonding interaction between the nearby conserved glutamate residue and the ribose ring of Adenosyl radical plays a crucial role in manipulating the orbital ordering

Sign in / Sign up

Export Citation Format

Share Document