scholarly journals Frontier molecular orbital effects control the hole-catalyzed racemization of atropisomeric biaryls

2019 ◽  
Vol 10 (8) ◽  
pp. 2285-2289 ◽  
Author(s):  
Jacqueline S. J. Tan ◽  
Robert S. Paton
Keyword(s):  
Transition State ◽  
Molecular Orbital ◽  
Frontier Molecular Orbital ◽  
Highest Occupied Molecular Orbital ◽  
Planar Transition

Biaryl atropisomerization is dramatically accelerated by the removal of an electron. The planar transition state is preferentially stabilized from depopulation of the highest occupied molecular orbital.

scholarly journals QTAIM investigation of bis(pyrazol-1-yl)methane derivative and its Zn(II) complexes (ZnLX2, X=Cl, Br or I)

2015 ◽  
Vol 80 (8) ◽  
pp. 997-1008 ◽  
Author(s):  
Maryam Dehestani ◽  
Leila Zeidabadinejad
Keyword(s):  
Molecular Orbital ◽  
Critical Points ◽  
Structural Parameters ◽  
Frontier Molecular Orbital ◽  
Orbital Energy ◽  
Theory Approach ◽  
Topological Parameters ◽  
Molecular Orbital Energy ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

Topological analyses of the electron density using the quantum theory of atoms in molecules (QTAIM) have been carried out at the B3PW91/6-31g (d) theoretical level, on bis(pyrazol-1-yl)methanes derivatives 9-(4-(di (1H-pyrazol-1-yl)-methyl)phenyl)-9H-carbazole (L) and its zinc(II) complexes: ZnLCl2 (1), ZnLBr2 (2) and ZnLI2 (3). The topological parameters derived from Bader theory were also analyzed; these are characteristics of Zn-bond critical points and also of ring critical points. The calculated structural parameters are the frontier molecular orbital energies highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), hardness (?), softness (S), the absolute electronegativity (?), the electrophilicity index (?) and the fractions of electrons transferred (?N) from ZnLX2 complexes to L. The numerous correlations and dependencies between energy terms of the Symmetry Adapted Perturbation Theory approach (SAPT), geometrical, topological and energetic parameters were detected and described.

scholarly journals Crystal Structure, Hirshfeld Surface and Frontier Molecular Orbital Analyses of N-[2-(trifluoromethyl)phenyl]succinamic Acid

2020 ◽  
Vol 32 (12) ◽  
pp. 3179-3185
Author(s):  
P.A. Suchetan ◽  
S. Naveen ◽  
N.K. Lokanath ◽  
P. Krishna Murthy ◽  
M.V. Deepa Urs
Keyword(s):  
Hydrogen Bonds ◽  
Molecular Orbital ◽  
Density Functional ◽  
Hirshfeld Surface ◽  
Basis Set ◽  
Frontier Molecular Orbital ◽  
Reactivity Descriptors ◽  
Succinamic Acid ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

The ortho-CF3 substituent and the N-H bond are in syn-conformation in N-[2-(trifluoromethyl)phenyl]succinamic acid. In amide and acid functionalities, the carbonyl groups are directed in opposite directions to each other and their related-CH2 groups. syn-Conformation is observed for the acid functionality, where the carbonyl C=O and hydroxyl O-H bonds are directed in the same direction. Three planar fragments comprise of the molecule: aromatic ring (A), core portion -Carm-N(H)-C(=O)-C(H2)-C(H2)(B) and -C(H2)-C(=O)-OH(C). The dihedral angle between a pair of fragments being 48.6(4)º (A and B), 81.6 (4)º (B and C) and 70.5 (5)º (A and C). N-H•••O hydrogen bonds bind the molecules forming C(4) chains in the crystal, and the neighbouring anti-parallel chains are bound by O-H•••O hydrogen bonds resulting in a chair shaped ribbon of one-dimensional nature. The Hirshfeld surface study was carried out, including fingerprint plots. Studies have shown that the interactions with O•••H/H•••O (27.4%), H•••H (27.3%) and H•••F/F•••H (20.2%) substantially added to the surface. Theoretically, the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and various global reactivity descriptors were also computed by the density functional theory (DFT/B3LYP) approach with a 6-311G(d, p) basis set in the ground state on the geometrically optimized structure in the gas phase.

Study of trichloronitrosomethane: regioselective cycloadditions of 2-substituted-1,3-butadienes

1989 ◽  
Vol 67 (12) ◽  
pp. 2153-2161 ◽  
Author(s):  
Cheng-Tung Lin ◽  
Wen-Jei Hsu
Keyword(s):  
Electron Transfer ◽  
Reaction Mechanism ◽  
Transition State ◽  
Molecular Orbital ◽  
Kinetic Studies ◽  
Frontier Molecular Orbital ◽  
Cycloaddition Reactions ◽  
Orientation Preference ◽  
Straight Lines ◽  
Concerted Reaction

The regioselectivity of cycloaddition reactions of trichloronitrosomethane (1) with 2-alkyl (R = Me, Et, i-Pr, t-Bu, CF3, Bz, and Cl) and 2-aryl (Ar = Ph, 4-CH3OPh, 4-CH3Ph, 3-CH3Ph, and 4-ClPh) 1,3-butadienes is described. The orientation of cycloaddition is substituent dependent, producing 2,5-disubstituted (para) and 2,4-disubstituted (meta) 3,6-dihydro-1,2-oxazines from 2-alkyl- and 2-aryl-1,3-butadienes respectively. Increasing the bulk of the substituent from methyl to tert-butyl in 2-alkyl-1,3-butadienes increases the regioselectivity. Kinetic studies in various solvents indicate that plots of log km/kH vs. Hammett σ+ values give straight lines with the ρ values lying between −0.60 and −0.91 for the reactions with 2-aryl-1,3-butadienes. A concerted reaction mechanism is proposed and the orientation preference is consistent with frontier molecular orbital predictions for 2-alkyl-1,3-butadienes. In the reactions with 2-aryl-1,3-butadienes, a transition state leading to a spin-paired diradical, which then converts by partial electron transfer to zwitterionic structure, is proposed. Keywords: trichloronitrosomethane, 3,6-dihydro-1,2-oxazine, regioselectivity, [2 + 4] cycloaddition.

Perspectives on the Role of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) in the Study of Chemical Reactivity: An Updated Review

2020 ◽  
Vol 24 (3) ◽  
pp. 314-331 ◽  
Author(s):  
Letícia S. Braga ◽  
Daniel H. S. Leal ◽  
Kamil Kuca ◽  
Teodorico C. Ramalho
Keyword(s):  
Molecular Orbital ◽  
Chemical Reactions ◽  
Chemical Reactivity ◽  
Molecular Orbitals ◽  
Frontier Molecular Orbital ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

Molecular orbitals are critical in the rationalization of several chemical reactions. Thus, the frontier molecular orbital theory, proposed by Fukui's group, postulated the importance of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) for chemical reactions. It should be kept in mind, however, that there are limitations of this theory and new perspectives about the chemical reactivity have recently been arisen based on composition and location of other frontier molecular orbitals. In this review, we have reported the development and the most recent applications of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) concept, which describes the breaking and formation of new chemical bonds and can in turn, provide important clues that modulate chemical reactivity of atoms and molecules.

scholarly journals Synthesis and Structural Studies of a New Complex of Di[hexabromobismuthate (III)] 2,5-Propylaminepyrazinium [C10H28N4]Bi2Br10

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Mohamed El Mehdi Touati ◽  
Habib Boughzala
Keyword(s):  
Molecular Orbital ◽  
Energy Gap ◽  
Frontier Molecular Orbital ◽  
Structural Studies ◽  
Scanning Calorimetry ◽  
Inorganic Hybrid ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Crystal Net

A new organic-inorganic hybrid material, [C10H28N4]Bi2Br10, has been synthesized and characterized. The compound crystallizes in monoclinic P21/c space group with a = 11.410(4) Å, b = 11.284(4) Å, c = 12.599(3) Å, β = 115.93(2)°, and V = 1458.8(8) Å3. The structure consists of discrete dinuclear [Bi2Br10]4− anions and [C10H28N4]4+ cations. It consists of a 0-D anion built up of edge-sharing bioctahedron. The crystal net contains N–H⋯Br hydrogen bonds. The differential scanning calorimetry (DSC) reveals an irreversible phase transition at −17°C. The frontier molecular orbital and the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) calculation allow the classification of the material as an insulator.

Chemical Behavior of Charge-transfer Complexes, VI. Catalysis of Acetolysis of 2,4,7-Trinitro-9-fluorenyl p-Toluenesulfonate by Aromatic Hydrocarbon Donors

1974 ◽  
Vol 52 (22) ◽  
pp. 3748-3757 ◽  
Author(s):  
Allan K. Colter ◽  
Arthur L. McKenna ◽  
M. A. Kasem
Keyword(s):  
Charge Transfer ◽  
Aromatic Hydrocarbon ◽  
Transition State ◽  
Molecular Orbital ◽  
Orbital Energy ◽  
Charge Transfer Complexes ◽  
Substrate Complex ◽  
Donor Substrate ◽  
Highest Occupied Molecular Orbital ◽  
Π Complex

The catalytic effectiveness of eleven aromatic hydrocarbon donors in the acetolysis of 2,4,7-trinitro-9-fluorenyl p-toluenesulfonate (TNF-OTs) has been examined. For nine of these donors, the kinetic data were analyzed to obtain the rate constant, kc, for acetolysis of the 1:1 donor–substrate complex, and the 1:1 donor–substrate association constant, K. Two measures of catalytic effectiveness, log kc and log kcK correlate well with the highest occupied molecular orbital energy of the donor, E(HOMO), calculated by the Hückel molecular orbital (HMO) method. The success of these correlations is considered to mean that the transition state for acetolysis resembles a π-complex. A model based on Mulliken's charge-transfer theory in its simplest form leads to an estimate of 0.11 of an electron transferred from the donor to the acceptor substrate in the complexed transition state.

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

scholarly journals Electronic Properties of Triangle Molybdenum Disulfide (MoS2) Clusters with Different Sizes and Edges

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1157
Author(s):  
Songsong Wang ◽  
Changliang Han ◽  
Liuqi Ye ◽  
Guiling Zhang ◽  
Yangyang Hu ◽  
...  
Keyword(s):  
Quantum Chemistry ◽  
Electronic Properties ◽  
Absorption Spectra ◽  
Molecular Orbital ◽  
Electronic Structures ◽  
Edge States ◽  
Frontier Orbitals ◽  
Edge Structure ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

The electronic structures and transition properties of three types of triangle MoS2 clusters, A (Mo edge passivated with two S atoms), B (Mo edge passivated with one S atom), and C (S edge) have been explored using quantum chemistry methods. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of B and C is larger than that of A, due to the absence of the dangling of edge S atoms. The frontier orbitals (FMOs) of A can be divided into two categories, edge states from S3p at the edge and hybrid states of Mo4d and S3p covering the whole cluster. Due to edge/corner states appearing in the FMOs of triangle MoS2 clusters, their absorption spectra show unique characteristics along with the edge structure and size.

scholarly journals First-Principles Study of Au-Doped InN Monolayer as Adsorbent and Gas Sensing Material for SF6 Decomposed Species

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1708
Author(s):  
Ruochen Peng ◽  
Qu Zhou ◽  
Wen Zeng
Keyword(s):  
Power Systems ◽  
Molecular Orbital ◽  
First Principles ◽  
Recovery Time ◽  
Sulfur Hexafluoride ◽  
Gas Sensing ◽  
Normal Operation ◽  
Frontier Molecular Orbital ◽  
Adsorption System ◽  
Sensing Material

As an insulating medium, sulfur hexafluoride (SF6) is extensively applied to electrical insulation equipment to ensure its normal operation. However, both partial discharge and overheating may cause SF6 to decompose, and then the insulation strength of electrical equipment will be reduced. The adsorption properties and sensing mechanisms of four SF6 decomposed components (HF, SO2, SOF2 and SO2F2) upon an Au-modified InN (Au-InN) monolayer were studied in this work based on first-principles theory. Meanwhile, the adsorption energy (Ead), charge transfer (QT), deformation charge density (DCD), density of states (DOS), frontier molecular orbital and recovery property were calculated. It can be observed that the structures of the SO2, SOF2 and SO2F2 molecules changed significantly after being adsorbed. Meanwhile, the Ead and QT of these three adsorption systems are relatively large, while that of the HF adsorption system is the opposite. These phenomena indicate that Au-InN monolayer has strong adsorption capacity for SO2, SOF2 and SO2F2, and the adsorption can be identified as chemisorption. In addition, through the analysis of frontier molecular orbital, it is found that the conductivity of Au-InN changed significantly after adsorbing SO2, SOF2 and SO2F2. Combined with the analysis of the recovery properties, since the recovery time of SO2 and SO2F2 removal from Au-InN monolayer is still very long at 418 K, Au-InN is more suitable as a scavenger for these two gases rather than as a gas sensor. Since the recovery time of the SOF2 adsorption system is short at 418 K, and the conductivity of the system before and after adsorption changes significantly, Au-InN is an ideal SOF2 gas-sensing material. These results show that Au-InN has broad application prospects as an SO2, SOF2 and SO2F2 scavenger and as a resistive SOF2 sensor, which is of extraordinary meaning to ensure the safe operation of power systems. Our calculations can offer a theoretical basis for further exploration of gas adsorbent and resistive sensors prepared by Au-InN.

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