Probing Intramolecular Interaction of Stereoisomers Using Computational Spectroscopy

2020 ◽  
Vol 73 (8) ◽  
pp. 813
Author(s):  
Feng Wang ◽  
Shawkat Islam ◽  
Frederick Backler
Keyword(s):  
Hydrogen Bonding ◽  
Binding Energy ◽  
Gas Phase ◽  
Intramolecular Interaction ◽  
Dipole Moments ◽  
Energy Difference ◽  
Binding Energies ◽  
Intramolecular Interactions ◽  
Computational Spectroscopy ◽  
Ionic States

Several model stereoisomers such as ferrocene (Fc), methoxyphenol, and furfural conformers are discussed. It was discovered that the Fc IR spectroscopic band(s) below 500cm−1 serve as fingerprints for eclipsed (splitting 17 (471–488)cm−1) and staggered Fc (splitting is ~2 (459–461)cm−1) in the gas phase. It is revealed that in the gas phase the dominance of the eclipsed Fc (D5h) at very low temperatures changes to a mixture of both eclipsed and staggered Fc when the temperature increases. However, in solvents such as CCl4, eclipsed Fc dominates at room temperature (300K) due to the additional solvation energy. Intramolecular interactions of organic model compounds such as methoxyphenols (guaiacol (GUA) and mequinol (MEQ)) and furfural, ionization energies such as the carbon 1s (core C1s), as well as valence binding energy spectra serve this purpose well. Hydrogen bonding alters the C1s binding energies of the methoxy carbon (C(7)) of anti-syn and anti-gauche conformers of GUA to 292.65 and 291.91eV, respectively. The trans and cis MEQ conformers, on the other hand, are nearly energy degenerate, whereas their dipole moments are significantly different: 2.66 Debye for cis and 0.63 Debye for trans-MEQ. Moreover, it is found that rotation around the Cring–OH and the Cring–OCH3 bonds differ in energy barrier height by ~0.50 kcal⋅mol−1. The Dyson orbital momentum profiles of the most different ionic states, 25a′ (0.35eV) and 3a′ (−0.33eV), between cis and trans-MEQ in outer valence space (which is measurable using electron momentum spectroscopy (EMS)), exhibit quantitative differences. Finally, the molecular switch from trans and cis-furfural engages with a small energy difference of 0.74 kcal mol−1, however, at the calculated C(3)(–H⋅⋅⋅O=C) site the C1s binding energy difference is 0.105eV (2.42 kcal mol−1) and the NMR chemical shift of the same carbon site is also significant; 7.58ppm from cis-furfural without hydrogen bonding.

scholarly journals np-Pair Correlations in the Isovector Pairing Model

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1405
Author(s):  
Feng Pan ◽  
Yingwen He ◽  
Lianrong Dai ◽  
Chong Qi ◽  
Jerry P. Draayer
Keyword(s):  
Binding Energy ◽  
Occupation Number ◽  
Mean Field ◽  
Energy Difference ◽  
Binding Energies ◽  
Pair Correlations ◽  
Isospin Symmetry Breaking ◽  
Pairing Model ◽  
Proton Pairing ◽  
Spin Basis

A diagonalization scheme for the shell model mean-field plus isovector pairing Hamiltonian in the O(5) tensor product basis of the quasi-spin SUΛ(2) ⊗ SUI(2) chain is proposed. The advantage of the diagonalization scheme lies in the fact that not only can the isospin-conserved, charge-independent isovector pairing interaction be analyzed, but also the isospin symmetry breaking cases. More importantly, the number operator of the np-pairs can be realized in this neutron and proton quasi-spin basis, with which the np-pair occupation number and its fluctuation at the J = 0+ ground state of the model can be evaluated. As examples of the application, binding energies and low-lying J = 0+ excited states of the even–even and odd–odd N∼Z ds-shell nuclei are fit in the model with the charge-independent approximation, from which the neutron–proton pairing contribution to the binding energy in the ds-shell nuclei is estimated. It is observed that the decrease in the double binding-energy difference for the odd–odd nuclei is mainly due to the symmetry energy and Wigner energy contribution to the binding energy that alter the pairing staggering patten. The np-pair amplitudes in the np-pair stripping or picking-up process of these N = Z nuclei are also calculated.

scholarly journals Geometries, Reactivity and Binding Energy of Urea on Mg9O9

2020 ◽  
Vol 5 (3) ◽  
Author(s):  
Antonio Luiz Almeida ◽  
João Batista Lopes Martins
Keyword(s):  
Binding Energy ◽  
Gas Phase ◽  
Chemical Potential ◽  
Function Analysis ◽  
Binding Energies ◽  
Chemical Hardness ◽  
Atomic Charges ◽  
Quantum Chemical Descriptors ◽  
Site Selectivity ◽  
Global And Local

In this paper we present global and local reactivity results of the urea gas phase molecule and gas phase (MgO)18 agglomerated for understand charge distribution and binding energy (MgO)-UREA. We analyze the quantum chemical descriptors, ionization potential (I), electron affinity (A), chemical hardness (ɳ), chemical potential (μ) and Global Philicity Index (ω) and site reactivity or site selectivity condensed Fukui function analysis of the distribution of atomic charges investigated with  methods of Mulliken, Merz-Kolman and Natural Atomic Charges. For instance, the binding energies of MgO-Urea systems are.

scholarly journals The binding energies of very light nuclei

1947 ◽  
Vol 191 (1024) ◽  
pp. 61-82 ◽  
Keyword(s):  
Binding Energy ◽  
Cosmic Ray ◽  
Energy Difference ◽  
Binding Energies ◽  
Fair Agreement ◽  
Light Nuclei ◽  
Meson Mass ◽  
Triplet States ◽  
Many Body ◽  
Static Interaction

The static interaction of the Møller-Rosenfeld theory is used to calculate approximately the binding energies of the nuclei H 2 , H 3 , He 3 and He 4 . The value of the meson mass and of the two other parameters available in the theory are determined from a comparison with the observed binding energies of the H 3 nucleus and of the singlet and triplet states of the deuteron. The meson mass so determined is between 210 and 220 electron masses which is in fair agreement with cosmic-ray measurements. The binding energy of He 3 calculated from the energy difference H 3 – He 3 is also found to be in fair agreement with the observed value. The theoretical binding energy of He 4 is less than half the observed value, and it is suggested that in this nucleus there exists an additional many-body interaction.

X-Ray Photoelectron Spectra of Aluminum Oxides: Structural Effects on the “Chemical Shift”

1973 ◽  
Vol 27 (1) ◽  
pp. 1-5 ◽  
Author(s):  
James R. Lindsay ◽  
Harry J. Rose ◽  
William E. Swartz ◽  
Plato H. Watts ◽  
Kenneth A. Rayburn
Keyword(s):  
Hydrogen Bonding ◽  
Binding Energy ◽  
Binding Energies ◽  
Photoelectron Spectra ◽  
Electrostatic Model ◽  
Structural Effects ◽  
Aluminum Oxides ◽  
X Ray ◽  
Structural Differences ◽  
Core Electrons

The aluminum (2p) electron spectra of several anhydrous and “hydrous” aluminum oxides have been recorded, and the binding energies have been measured. A simple electrostatic model is employed to explain the observed shift in binding energy and relate it to differences in structure and hydrogen bonding. Two conclusions can be drawn: structural differences must be considered when interpreting photoelectron spectra for inorganic crystalline substances; and hydrogen bonding with anions may have a measurable effect on the binding energy of core electrons of the cations.

scholarly journals Segregation effect and N2 binding energy reduction in CO-N2 systems adsorbed on water ice substrates

2018 ◽  
Vol 619 ◽  
pp. A111 ◽  
Author(s):  
T. Nguyen ◽  
S. Baouche ◽  
E. Congiu ◽  
S. Diana ◽  
L. Pagani ◽  
...  
Keyword(s):  
Binding Energy ◽  
Gas Phase ◽  
Adsorption Energy ◽  
High Vacuum ◽  
Amorphous Solid ◽  
Abundant Species ◽  
Binding Energies ◽  
Ultra High Vacuum ◽  
Pure Species ◽  
Water Ice

Context. CO and N2 are two abundant species in molecular clouds. CO molecules are heavily depleted from the gas phase towards the centre of pre-stellar cores, whereas N2 maintains a high gas phase abundance. For example, in the molecular cloud L183, CO is depleted by a factor of ≈400 in its centre with respect to the outer regions of the cloud, whereas N2 is only depleted by a factor of ≈20. The reason for this difference is not yet clear, since CO and N2 have identical masses, similar sticking properties, and a relatively close energy of adsorption. Aims. We present a study of the CO-N2 system in sub-monolayer regimes, with the aim to measure, analyse and elucidate how the adsorption energy of the two species varies with coverage, with much attention to the case where CO is more abundant than N2. Methods. Experiments were carried out using the ultra-high vacuum (UHV) set-up called VENUS. Sub-monolayers of either pure 13CO or pure 15N2 and 13CO:15N2 mixtures were deposited on compact amorphous solid water ice, and crystalline water ice. Temperature-programmed desorption experiments, monitored by mass spectrometry, are used to analyse the distributions of binding energies of 13CO and 15N2 when adsorbed together in different proportions. Results. The distribution of binding energies of pure species varies from 990 K to 1630 K for 13CO, and from 890 K to 1430 K for 15N2. When a CO:N2 mixture is deposited, the 15N2 binding energy distribution is strongly affected by the presence of 13CO, whereas the adsorption energy of CO is unaltered. Conclusions. Whatever types of water ice substrate we used, the N2 effective binding energy was significantly lowered by the presence of CO molecules. We discuss the possible impact of this finding in the context of pre-stellar cores.

Intermolecular interactions between tropolone and fluoromethanes

2001 ◽  
Vol 79 (2-3) ◽  
pp. 483-499 ◽  
Author(s):  
V J MacKenzie ◽  
R P Steer
Keyword(s):  
Hydrogen Bonding ◽  
Binding Energy ◽  
Potential Energy Surfaces ◽  
Solvent Molecule ◽  
Binding Energies ◽  
Entire Group ◽  
Proton Affinities ◽  
Fluorescence Excitation ◽  
Proton Tunneling ◽  
Free Jet

Van der Waals complexes of tropolone (TRN) with CF4, CFH3, CF2H2, and CF3H have been synthesized by expanding mixtures of TRN and the fluorinated methane (FM) in a supersonic free-jet and have been examined using laser induced fluorescence excitation spectroscopy. The sign and magnitude of the microscopic solvent shifts and the magnitude of the tunneling doublet splittings of the origin bands of each distinct complex have been determined from the LIFE spectra. These data, together with both empirical and ab initio calculations of the potential energy surfaces of the 1:1 complexes, have been used to assign the structures of the complexes and determine their approximate binding energies. Expansion of TRN with CF4 produces one identifiable 1:1 complex in which the solvent is primarily dispersively bound and lies above the TRN ring in a symmetric three-legged stool conformation. Expansion of TRN with CFH3 produces two 1:1 complexes, both primarily dispersively bound, in which the solvent molecule lies above the seven-membered ring of TRN in a three-legged stool conformation but which differ in the conformational orientation of the CFH3 species on the TRN surface. Expansion of TRN with CF2H2 produces one 1:1 complex in which the solvent molecule lies above the plane of the TRN ring, but is considerably displaced from its centre of mass and in which binding is primarily electrostatic rather than dispersive. All three partially fluorinated methane molecules produce 1:1 complexes with TRN in which the solvent is bound in the TRN plane by intermolecular hygrogen-bonding. Such structures partially disrupt the intramolecular hydrogen bond of the chromophore and consequently exhibit LIFE spectra characterized by intense, strongly blue-shifted origin bands in which the proton tunneling doublets are unresolvable because of a large decrease in the intramolecular proton tunneling rate. The existence of good correlations between the solute-solvent binding energy and the microscopic solvent shift and between the binding energy and the proton affinities of the solvent for the entire group of hydrogen-bonding solvents, including the partially fluorinated methanes, suggests that C–F ... H–O and F–C–H ... O = C interactions result in weak hydrogen bonds which are not qualitatively different from those of more traditional hydrogen-bonding species. PACS No.: 33.20L, 35.20B

Influence of geometry on positron binding to molecules

2021 ◽  
Author(s):  
J R Danielson ◽  
Soumen Ghosh ◽  
clifford surko
Keyword(s):  
Dipole Moment ◽  
Binding Energy ◽  
Positron Annihilation ◽  
Significant Role ◽  
Dipole Moments ◽  
Molecular Size ◽  
Molecular Geometry ◽  
Binding Energies ◽  
Molecular Polarizability ◽  
Global Parameters

Abstract Annihilation studies have established that positrons bind to most molecules. They also provide measurements of the positron-molecule binding energies, which are found to vary widely and depend upon molecular size and composition. Trends of binding energy with global parameters such as molecular polarizability and dipole moment have been discussed previously. In this paper, the dependence of binding energy on molecular geometry is investigated by studying resonant positron annihilation on selected pairs of isomers. It is found that molecular geometry can play a significant role in determining the binding energies even for isomers with very similar polarizabilities and dipole moments. The possible origins of this dependence are discussed.

A DFT study of spherands containing five anisyl groups — Highly preorganized to bind the alkali metal

2006 ◽  
Vol 84 (8) ◽  
pp. 1045-1049 ◽  
Author(s):  
Shabaan AK Elroby ◽  
Kyu Hwan Lee ◽  
Seung Joo Cho ◽  
Alan Hinchliffe
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Density Functional ◽  
Ionic Radius ◽  
Binding Energies ◽  
Cavity Size ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Good Agreement

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.

scholarly journals Large Stabilization Effects by Intramolecular Beryllium Bonds in Ortho-Benzene Derivatives

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3401
Author(s):  
Tsai I-Ting ◽  
M. Merced Montero-Campillo ◽  
Ibon Alkorta ◽  
José Elguero ◽  
Manuel Yáñez
Keyword(s):  
Reaction Scheme ◽  
Binding Energies ◽  
Intramolecular Interactions ◽  
Isodesmic Reaction ◽  
Bond Critical Point ◽  
Interaction Energies ◽  
Benzene Derivatives ◽  
Covalent Interaction ◽  
Beryllium Bond ◽  
Donor And Acceptor

Intramolecular interactions are shown to be key for favoring a given structure in systems with a variety of conformers. In ortho-substituted benzene derivatives including a beryllium moiety, beryllium bonds provide very large stabilizations with respect to non-bound conformers and enthalpy differences above one hundred kJ·mol−1 are found in the most favorable cases, especially if the newly formed rings are five or six-membered heterocycles. These values are in general significantly larger than hydrogen bonds in 1,2-dihidroxybenzene. Conformers stabilized by a beryllium bond exhibit the typical features of this non-covalent interaction, such as the presence of a bond critical point according to the topology of the electron density, positive Laplacian values, significant geometrical distortions and strong interaction energies between the donor and acceptor quantified by using the Natural Bond Orbital approach. An isodesmic reaction scheme is used as a tool to measure the strength of the beryllium bond in these systems in terms of isodesmic energies (analogous to binding energies), interaction energies and deformation energies. This approach shows that a huge amount of energy is spent on deforming the donor–acceptor pairs to form the new rings.

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