scholarly journals Anion–Anion Interactions in Aerogen-Bonded Complexes. Influence of Solvent Environment

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2116
Author(s):  
Anna Grabarz ◽  
Mariusz Michalczyk ◽  
Wiktor Zierkiewicz ◽  
Steve Scheiner
Keyword(s):  
Gas Phase ◽  
Binding Energies ◽  
Stable Complex ◽  
Polar Solvents ◽  
Small Energy ◽  
Polar Medium ◽  
Molecular Plane ◽  
Aqueous Solvent ◽  
Solvent Environment ◽  
Influence Of Solvent

Ab initio calculations are applied to the question as to whether a AeX5− anion (Ae = Kr, Xe) can engage in a stable complex with another anion: F−, Cl−, or CN−. The latter approaches the central Ae atom from above the molecular plane, along its C5 axis. While the electrostatic repulsion between the two anions prevents their association in the gas phase, immersion of the system in a polar medium allows dimerization to proceed. The aerogen bond is a weak one, with binding energies less than 2 kcal/mol, even in highly polar aqueous solvent. The complexes are metastable in the less polar solvents THF and DMF, with dissociation opposed by a small energy barrier.

Comparison of Anion‐Anion Halogen Bonds with Neutral‐Anion Halogen Bonds in the Gas Phase and Polar Solvents

ChemPlusChem ◽  
2021 ◽  
Vol 86 (2) ◽  
pp. 232-240
Author(s):  
Ying Li ◽  
Lingpeng Meng ◽  
Yanli Zeng
Keyword(s):  
Gas Phase ◽  
Halogen Bonds ◽  
Polar Solvents

Serine–Ca2+ versus serine–Cu2+ complexes — A theoretical perspective

2010 ◽  
Vol 88 (8) ◽  
pp. 759-768 ◽  
Author(s):  
Al Mokhtar Lamsabhi ◽  
Otilia Mó ◽  
Manuel Yáñez
Keyword(s):  
Gas Phase ◽  
Electron Density ◽  
Potential Energy Surfaces ◽  
Metal Ion ◽  
Theoretical Perspective ◽  
Binding Energies ◽  
Interacting Systems ◽  
Intramolecular Hydrogen ◽  
Energy Surfaces ◽  
Doubly Charged

The association of Ca2+ and Cu2+ to serine was investigated by means of B3LYP DFT calculations. The [serine–M]2+ (M = Ca, Cu) potential energy surfaces include, as does the neutral serine, a large number of conformers, in which a drastic reorganization of the electron density of the serine moiety is observed. This leads to significant changes in the number and strength of the intramolecular hydrogen bonds existing in the neutral serine tautomers. In some cases, a proton is transferred from the carboxylic OH group to the amino group and accordingly, some of the more stable [serine–M]2+ complexes can be viewed as the result of the interaction of the zwiterionic form of serine with the doubly charged metal ion. Whereas the interaction between Ca2+ and serine is essentially electrostatic, that between Cu2+ and serine has a non-negligible covalent character, reflected in larger electron densities at the bond critical points between the metal and the base, in the negative values of the electron density between the two interacting systems, and in much larger Cu2+ than Ca2+ binding energies. More importantly, the interaction with Cu2+ is followed by a partial oxidation of the base, which is not observed when the metal ion is Ca2+. The main consequence is that in Cu2+ complexes a significant acidity enhancement of the serine moiety takes place, which strongly favors the deprotonation of the [serine–Cu]2+ complexes. This is not the case for Ca2+ complexes. Thus, [serine–Ca]2+ complexes, like those formed by urea, thiourea, selenourea, or glycine, should be detected in the gas phase. Conversely, the complexes with Cu2+ should deprotonate spontaneously and therefore only [(serine–H)–Cu]+ monocations should be experimentally accessible.

scholarly journals Efficient utilization of renewable feedstocks: the role of catalysis and process design

2017 ◽  
Vol 376 (2110) ◽  
pp. 20170064 ◽  
Author(s):  
Regina Palkovits ◽  
Irina Delidovich
Keyword(s):  
Elevated Temperature ◽  
Gas Phase ◽  
Process Design ◽  
Circular Economy ◽  
Paradigm Shift ◽  
Efficient Utilization ◽  
Polar Solvents ◽  
Platform Chemicals ◽  
Renewable Feedstocks

Renewable carbon feedstocks such as biomass and CO 2 present an important element of future circular economy. Especially biomass as highly functionalized feedstock provides manifold opportunities for the transformation into attractive platform chemicals. However, this change of the resources requires a paradigm shift in refinery design. Fossil feedstocks are processed in gas phase at elevated temperature. In contrast, biorefineries are based on processes in polar solvents at moderate conditions to selectively deoxygenate the polar, often thermally instable and high-boiling molecules. Here, challenges of catalytic deoxygenation, novel strategies for separation and opportunities provided at the interface to biotechnology are discussed in form of showcases. This article is part of a discussion meeting issue ‘Providing sustainable catalytic solutions for a rapidly changing world’.

scholarly journals Spectral properties of coumarin derivatives in various environments

2013 ◽  
Vol 11 (4) ◽  
pp. 492-501 ◽  
Author(s):  
Alzbeta Holubekova ◽  
Pavel Mach ◽  
Jan Urban
Keyword(s):  
Gas Phase ◽  
Absorption Spectra ◽  
Spectral Properties ◽  
Density Functional ◽  
Water Solution ◽  
Blue Shift ◽  
Coumarin Derivatives ◽  
Complex Environments ◽  
Td Dft ◽  
Solvent Environment

AbstractThe structural and spectral properties of coumarin derivatives in complex environments were investigated within the time-dependent density functional theory (TD DFT). Absorption spectra calculations were obtained at TD PBE0/6-31+G(d,p) level of theory for coumarin47 in the gas-phase and in various polar and non-polar organic solvents. The geometries of coumarins 6, 30, 47 and 522 in the gas phase and in inclusion complexes with the β-cyclodextrin (βCD) were determined by PM3 and DFT (HCTH/6-31G) calculations. Encapsulation of coumarin in βCD and associated changes in electronic structure produced either a red or blue shift in the absorption spectra of coumarins. A proposed cavity model for βCD-coumarin complex in water solution allowed identification of various contributions to the overall shift in the absorption spectra of coumarin upon complex formation in a solvent environment

scholarly journals Absorption mechanism, structural and electronic properties of MC19 (M = B and Si) fullerenes with 1-acetylpiperazine

2017 ◽  
Vol 36 (1-2) ◽  
pp. 797-804
Author(s):  
Özgür Alver ◽  
Cemal Parlak ◽  
Mohamed I Elzagheid ◽  
Ponnadurai Ramasami
Keyword(s):  
Electronic Properties ◽  
Gas Phase ◽  
Basis Set ◽  
Stable Complex ◽  
Absorption Mechanism ◽  
Boron Doped ◽  
Structural And Electronic Properties ◽  
Influence Of Water ◽  
Vibrational Bands ◽  
Silicon Doped

The interaction mechanisms of undoped, silicon- and boron-doped C20 fullerenes and 1-acetylpiperazine (1-ap) were investigated. Stability, electronic properties, influence of water on the solubility and stability, molecular parameters, descriptive vibrational bands and nuclear magnetic resonance shielding values are reported. The quantum mechanical calculations were carried out using the M06-2X functional and the 6-31G(d) basis set. It is observed that all the complexes are more stabilized in water compared to the gas phase. The most stable complex was found as silicon-doped fullerene interacting with the carbonyl edge of 1-ap releasing energy of 64.13 kcal/mol in water.

scholarly journals Electronic Spectroscopy of Isolated DNA Polyanions

2018 ◽  
Author(s):  
Steven Daly ◽  
Massimiliano Porrini ◽  
Frédéric Rosu ◽  
Valerie Gabelica
Keyword(s):  
Gas Phase ◽  
Absorption Spectra ◽  
Ion Mobility ◽  
Photoelectron Spectroscopy ◽  
Binding Energies ◽  
Action Spectroscopy ◽  
Action Spectra ◽  
Vis Spectroscopy ◽  
Electron Binding Energies ◽  
Electron Binding

In solution, UV-vis spectroscopy is often used to investigate structural changes in biomolecules (i.e., nucleic acids), owing to changes in the environment of their chromophores (i.e., the nucleobases). Here we address whether action spectroscopy could achieve the same for gas-phase ions, while taking the advantage of additional mass spectrometry and ion mobility separation of complex mixtures. We therefore systematically studied the action spectroscopy of homo-base 6-mer DNA strands (dG6, dA6, dC6, dT6), and discuss the results in light of gas-phase structures validated by ion mobility spectrometry and infrared ion spectroscopy, and in light of electron binding energies measured by photoelectron spectroscopy, and calculated electronic photo-absorption spectra. When UV photons interact with oligonucleotide polyanions, two main actions may take place: (1) fragmentation and (2) electron detachment. The action spectra reconstructed from fragmentation follow the absorption spectra well, and result from multiple cycles of absorption and internal conversion. The action spectra reconstructed from the electron photodetachment (EPD) efficiency reveal interesting phenomena: EPD depends on the charge state in a manner depending on electron binding energies, and is particularly efficient for purines but not pyrimidines. EPD thus reflects not only absorption, but also particular relaxation pathways of the electronic excited states. As these pathways lead to photo-oxidation, their investigation on model gas-phase systems may prove useful to elucidate mechanisms of photo-oxidative damages, which are linked to mutations and cancers.

Theoretical insight into the substituent effects on the antioxidant properties of 8-hydroxyquinoline derivatives in gas phase and in polar solvents

2018 ◽  
Vol 96 (5) ◽  
pp. 453-458
Author(s):  
Anes El-Hadj Saïd ◽  
Sidi Mohamed Mekelleche ◽  
Taki-Eddine Ahmed Ardjani
Keyword(s):  
Electron Transfer ◽  
Gas Phase ◽  
Antioxidant Properties ◽  
Substituent Effects ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Antioxidant Power ◽  
Theoretical Insight ◽  
Insight Into

The objective of this work is to perform a theoretical analysis of the antioxidant properties of a series of 8-hydroxyquinolines (8-HQs) to rationalize the available experimental results and to design new potent 8-HQ derivatives. The study was carried out in gas phase and in methanol at the DFT/B3LYP/ 6-311++G(d,p) computational level. The formation of stable ArO• radicals is discussed on the basis of different mechanisms, namely, hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and single proton loss electron transfer (SPLET). The obtained results show that the HAT mechanism is, thermodynamically, more favoured in gas phase, whereas the SPLET pathway is more favoured in polar solvents. The calculated thermochemical descriptors allow classification of the antioxidant power of the studied compounds.

scholarly journals Towards the Application of Supramolecular Self-Associating Amphiphiles as Next-Generation Delivery Vehicles

Molecules ◽  
2020 ◽  
Vol 25 (18) ◽  
pp. 4126
Author(s):  
Lisa J. White ◽  
Jessica E. Boles ◽  
Kira L. F. Hilton ◽  
Rebecca J. Ellaby ◽  
Jennifer R. Hiscock
Keyword(s):  
Gas Phase ◽  
High Resolution Mass Spectrometry ◽  
Next Generation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Guest Species ◽  
Solvent Environment ◽  
Delivery Vehicles ◽  
Self Association ◽  
Aqueous Conditions

Herein, we present a series of supramolecular self-associating amphiphilic (SSA) salts and establish the potential for these molecular constructs to act as next-generation solution-state molecular delivery vehicles. We characterise the self-association of these SSAs, both alone and when co-formulated with a variety of drug(like) competitive guest species. Single crystal X-ray diffraction studies enable the observation of hydrogen-bonded self-association events in the solid state, whilst high resolution mass spectrometry confirms the presence of anionic SSA dimers in the gas-phase. These same anionic SSA dimeric species are also identified within a competitive organic solvent environment (DMSO-d6/0.5% H2O). However, extended self-associated aggregates are observed to form under aqueous conditions (H2O/5.0% EtOH) in both the absence and presence of these competitive guest species. Finally, through the completion of these studies, we present a framework to support others in the characterisation of such systems.

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