scholarly journals On the Role of the Electron-Dipole Interaction in Photodetachment Angular Distributions

2021 ◽  
Author(s):  
C. Annie Hart ◽  
Justin Lyle ◽  
Joseph Spellberg ◽  
Anna I. Krylov ◽  
Richard Mabbs
Keyword(s):  
Computational Study ◽  
Free Particle ◽  
Dipole Interaction ◽  
Chem Phys ◽  
Point Dipole ◽  
Photoelectron Imaging ◽  
Photodetachment Cross Section ◽  
Molecule Interactions ◽  
Near Threshold

The importance of including long-range electron-molecule interactions in treatments of photodetachment/photoionization is demonstrated. A combined experimental and computational study of CN− detachment is presented in which near threshold anisotropy parameters (β) are measured via photoelectron imaging. Calculated β values, based on an EOM-IP-CCSD/aug-cc-pVTZ Dyson orbital, are obtained using free particle and point dipole models. The results demonstrate the influence of the molecular dipole moment in the detachment process, and provide an explanation of the near threshold behavior of the overall photodetachment cross section in CN− detachment [J. Chem. Phys. 2020, 153, 184309]

scholarly journals The Activating Effect of Strong Acid for Pd-Catalyzed Directed C–H Activation by Concerted Metalation-Deprotonation Mechanism

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4083
Author(s):  
Heming Jiang ◽  
Tian-Yu Sun
Keyword(s):  
Activation Energy ◽  
Dft Calculations ◽  
Energy Barrier ◽  
Computational Study ◽  
Strong Acid ◽  
Activation Energy Barrier ◽  
Pd Catalysts ◽  
Acid Ligand ◽  
Strong Acids

A computational study on the origin of the activating effect for Pd-catalyzed directed C–H activation by the concerted metalation-deprotonation (CMD) mechanism is conducted. DFT calculations indicate that strong acids can make Pd catalysts coordinate with directing groups (DGs) of the substrates more strongly and lower the C–H activation energy barrier. For the CMD mechanism, the electrophilicity of the Pd center and the basicity of the corresponding acid ligand for deprotonating the C–H bond are vital to the overall C–H activation energy barrier. Furthermore, this rule might disclose the role of some additives for C–H activation.

scholarly journals Antioxidant Properties of Ergosterol and Its Role in Yeast Resistance to Oxidation

Antioxidants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1024
Author(s):  
Sebastien Dupont ◽  
Paul Fleurat-Lessard ◽  
Richtier Gonçalves Cruz ◽  
Céline Lafarge ◽  
Cédric Grangeteau ◽  
...  
Keyword(s):  
Computational Study ◽  
Antioxidant Properties ◽  
Beneficial Effects ◽  
Tert Butyl Hydroperoxide ◽  
Resistance To Oxidation ◽  
Specific Accumulation ◽  
The Subject

Although the functions and structural roles of sterols have been the subject of numerous studies, the reasons for the diversity of sterols in the different eukaryotic kingdoms remain unclear. It is thought that the specificity of sterols is linked to unidentified supplementary functions that could enable organisms to be better adapted to their environment. Ergosterol is accumulated by late branching fungi that encounter oxidative perturbations in their interfacial habitats. Here, we investigated the antioxidant properties of ergosterol using in vivo, in vitro, and in silico approaches. The results showed that ergosterol is involved in yeast resistance to tert-butyl hydroperoxide and protects lipids against oxidation in liposomes. A computational study based on quantum chemistry revealed that this protection could be related to its antioxidant properties operating through an electron transfer followed by a proton transfer mechanism. This study demonstrates the antioxidant role of ergosterol and proposes knowledge elements to explain the specific accumulation of this sterol in late branching fungi. Ergosterol, as a natural antioxidant molecule, could also play a role in the incompletely understood beneficial effects of some mushrooms on health.

The important role of non-covalent interactions for the vibrational circular dichroism of lactic acid in aqueous solution

2021 ◽  
Author(s):  
Sascha Jähnigen ◽  
Daniel Sebastiani ◽  
Rodolphe Vuilleumier
Keyword(s):  
Lactic Acid ◽  
Circular Dichroism ◽  
Computational Study ◽  
Bulk Water ◽  
Vibrational Circular Dichroism ◽  
Ab Initio Molecular Dynamics ◽  
Non Covalent Interactions ◽  
Circular Dichroïsm ◽  
Covalent Interactions

We present a computational study of vibrational circular dichroism (VCD) in solutions of (S)-lactic acid, relying on ab initio molecular dynamics (AIMD) and full solvation with bulk water. We discuss...

Role of the Electron–Dipole Interaction in Photodetachment Angular Distributions

2021 ◽  
pp. 10086-10092
Author(s):  
C. Annie Hart ◽  
Justin Lyle ◽  
Joseph Spellberg ◽  
Anna I. Krylov ◽  
Richard Mabbs
Keyword(s):  
Dipole Interaction ◽  
Angular Distributions

scholarly journals Frequency dispersion reveals chromophore diversity and colour-tuning mechanism in parrot feathers

2018 ◽  
Vol 5 (7) ◽  
pp. 172010 ◽  
Author(s):  
Jonathan E. Barnsley ◽  
Elliot J. Tay ◽  
Keith C. Gordon ◽  
Daniel B. Thomas
Keyword(s):  
Frequency Dispersion ◽  
Animal Coloration ◽  
Molecular Conformations ◽  
Tuning Mechanism ◽  
Resonance Raman Spectra ◽  
Molecule Interactions ◽  
Yellow Region ◽  
Colour Tuning

Variation in animal coloration is often viewed as the result of chemically distinct pigments conferring different hues. The role of molecular environment on hue tends to be overlooked as analyses are mostly performed on free pigments extracted from the integument. Here we analysed psittacofulvin pigments within parrot feathers to explore whether the in situ organization of pigments may have an effect on hue. Resonance Raman spectra from a red region of a yellow-naped amazon Amazona auropalliata tail feather show frequency dispersion, a phenomenon that is related to the presence of a range of molecular conformations (and multiple chromophores) in the pigment, whereas spectra from a yellow region on the same feather do not show the same evidence for multiple chromophores. Our findings are consistent with non-isomeric psittacofulvin pigments behaving as a single chromophore in yellow feather barbs, which implies that psittacofulvins are dispersed into a structurally disordered mixture in yellow feathers compared with red feathers. Frequency dispersion in red barbs may instead indicate that pigments are structurally organized through molecule–molecule interactions. Major differences in the hues of parrot feathers are thus associated with differences in the organization of pigments within feathers.

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