Molecules

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4 pages, 194 KiB

Open AccessEditorial

Introduction to “Intramolecular Hydrogen Bonding 2018”

by Goar Sánchez

Molecules 2019, 24(16), 2858; https://doi.org/10.3390/molecules24162858 - 7 Aug 2019

Cited by 10 | Viewed by 2718

Abstract

Non-covalent interactions have attracted the scientific attention during last decades as observed by the numerous studies in the literature [...] Full article

(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2018)

Research

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12 pages, 946 KiB

Open AccessArticle

Cis/Trans Energetics in Epoxide, Thiirane, Aziridine and Phosphirane Containing Cyclopentanols: Effects of Intramolecular OH⋯O, S, N and P Contacts

by Ben E. Smith, Jeremy M. Carr and Gregory S. Tschumper

Molecules 2019, 24(14), 2523; https://doi.org/10.3390/molecules24142523 - 10 Jul 2019

Cited by 2 | Viewed by 3204

Abstract

A recent computational analysis of the stabilizing intramolecular OH⋯O contact in 1,2-dialkyl-2,3-epoxycyclopentanol diastereomers has been extended to thiiriane, aziridine and phosphirane analogues. Density functional theory (DFT), second-order Møller-Plesset perturbation theory (MP2) and CCSD(T) coupled-cluster computations with simple methyl and ethyl substituents indicate that [...] Read more.

A recent computational analysis of the stabilizing intramolecular OH⋯O contact in 1,2-dialkyl-2,3-epoxycyclopentanol diastereomers has been extended to thiiriane, aziridine and phosphirane analogues. Density functional theory (DFT), second-order Møller-Plesset perturbation theory (MP2) and CCSD(T) coupled-cluster computations with simple methyl and ethyl substituents indicate that electronic energies of the

c i s

isomers are lowered by roughly 3 to 4 kcal mol⁻¹ when the OH group of these cyclopentanol systems forms an intramolecular contact with the O, S, N or P atom on the adjacent carbon. The results also suggest that S and P can participate in these stabilizing intramolecular interactions as effectively as O and N in constrained molecular environments. The stabilizing intramolecular OH⋯O, OH⋯S, OH⋯N and OH⋯P contacts also increase the covalent OH bond length and significantly decrease the OH stretching vibrational frequency in every system with shifts typically on the order of −41 cm⁻¹. Full article

(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2018)

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13 pages, 2061 KiB

Open AccessFeature PaperArticle

Cooperative Effects in Weak Interactions: Enhancement of Tetrel Bonds by Intramolecular Hydrogen Bonds

by Cristina Trujillo, Ibon Alkorta, José Elguero and Goar Sánchez-Sanz

Molecules 2019, 24(2), 308; https://doi.org/10.3390/molecules24020308 - 16 Jan 2019

Cited by 23 | Viewed by 3541

Abstract

A series of silyl and germanium complexes containing halogen atoms (fluorine and chlorine atoms) and exhibiting tetrel bonds with Lewis bases were analyzed by means of Møller-Plesset computational theory. Binding energies of germanium derivatives were more negative than silicon ones. Amongst the different [...] Read more.

A series of silyl and germanium complexes containing halogen atoms (fluorine and chlorine atoms) and exhibiting tetrel bonds with Lewis bases were analyzed by means of Møller-Plesset computational theory. Binding energies of germanium derivatives were more negative than silicon ones. Amongst the different Lewis bases utilized, ammonia produced the strongest tetrel bonded complexes in both Ge and Si cases, and substitution of the F atom by Cl led to stronger complexes with an ethylene backbone. However, with phenyl backbones, the fluorosilyl complexes were shown to be less stable than the chlorosilyl ones, but the opposite occurred for halogermanium complexes. In all the cases studied, the presence of a hydroxyl group enhanced the tetrel bond. That effect becomes more remarkable when an intramolecular hydrogen bond between the halogen and the hydrogen atom of the hydroxyl group takes places. Full article

(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2018)

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13 pages, 4862 KiB

Open AccessArticle

Assessing Parameter Suitability for the Strength Evaluation of Intramolecular Resonance Assisted Hydrogen Bonding in o-Carbonyl Hydroquinones

by Maximiliano Martínez-Cifuentes, Matías Monroy-Cárdenas, Juan Pablo Millas-Vargas, Boris E. Weiss-López and Ramiro Araya-Maturana

Molecules 2019, 24(2), 280; https://doi.org/10.3390/molecules24020280 - 14 Jan 2019

Cited by 10 | Viewed by 3469

Abstract

Intramolecular hydrogen bond (IMHB) interactions have attracted considerable attention due to their central role in molecular structure, chemical reactivity, and interactions of biologically active molecules. Precise correlations of the strength of IMHB’s with experimental parameters are a key goal in order to model [...] Read more.

Intramolecular hydrogen bond (IMHB) interactions have attracted considerable attention due to their central role in molecular structure, chemical reactivity, and interactions of biologically active molecules. Precise correlations of the strength of IMHB’s with experimental parameters are a key goal in order to model compounds for drug discovery. In this work, we carry out an experimental (NMR) and theoretical (DFT) study of the IMHB in a series of structurally similar o-carbonyl hydroquinones. Geometrical parameters, as well as Natural Bond Orbital (NBO) and Quantum Theory of Atoms in Molecules (QTAIM) parameters for IMHB were compared with experimental NMR data. Three DFT functionals were employed to calculated theoretical parameters: B3LYP, M06-2X, and ωB97XD. O^…H distance is the most suitable geometrical parameter to distinguish among similar IMHBs. Second order stabilization energies ΔE_ij⁽²⁾ from NBO analysis and hydrogen bond energy (E_HB) obtained from QTAIM analysis also properly distinguishes the order in strength of the studied IMHB. ΔE_ij⁽²⁾ from NBO give values for the IMHB below 30 kcal/mol, while E_HB from QTAIM analysis give values above 30 kcal/mol. In all cases, the calculated parameters using ωB97XD give the best correlations with experimental ¹H-NMR chemical shifts for the IMHB, with R² values around 0.89. Although the results show that these parameters correctly reflect the strength of the IMHB, when the weakest one is removed from the analysis, arguing experimental considerations, correlations improve significantly to values around 0.95 for R². Full article

(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2018)

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6 pages, 1408 KiB

Open AccessArticle

Exotic Spectra and Lattice Vibrations of Ice X Using the DFT Method

by Lu Jiang, Shu-Kai Yao, Kai Zhang, Ze-Ren Wang, Hui-Wen Luo, Xu-Liang Zhu, Yue Gu and Peng Zhang

Molecules 2018, 23(11), 2780; https://doi.org/10.3390/molecules23112780 - 26 Oct 2018

Cited by 9 | Viewed by 4863

Abstract

A typical vibrational spectrum in the ice phase has four separate bands: Translation, libration, bending, and stretching. Ice X, the final ice phase under high pressure, shows an exotic vibrational spectrum. Based on harmonic approximation, an ideal crystal of ice X has one [...] Read more.

A typical vibrational spectrum in the ice phase has four separate bands: Translation, libration, bending, and stretching. Ice X, the final ice phase under high pressure, shows an exotic vibrational spectrum. Based on harmonic approximation, an ideal crystal of ice X has one peak, at 998 cm⁻¹, for Raman scattering and two peaks, at 450 cm⁻¹ and 1507 cm⁻¹, for infrared absorption in this work. These three characteristic peaks are indicators of the phase transition between ice VII and VIII and ice X. Despite many experimental and theoretical works on ice X, only this study has clearly indicated these characteristic peaks in the region of the IR band. The phonon density of states shows quite different features than ice VIII, which could be verified by inelastic neutron scattering in the future. The dynamic processes of 15 vibrational normal modes are discussed and the typical hydrogen bonds are missing. Full article

(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2018)

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11 pages, 936 KiB

Open AccessArticle

Measurements, Thermodynamic Modeling, and a Hydrogen Bonding Study on the Solubilities of Metoprolol Succinate in Organic Solvents

by Jian Shen, Xianrui Liang and Hao Lei

Molecules 2018, 23(10), 2469; https://doi.org/10.3390/molecules23102469 - 26 Sep 2018

Cited by 12 | Viewed by 4288

Abstract

The solubilities of metoprolol succinate (a cardioselective β1 adrenergic receptor) in methanol, ethanol, n-propanol, isopropanol, n-butanol, ethyl acetate, and acetone were measured at temperatures ranging from (278.2 to 318.2) K using a solid–liquid equilibrium method. The solubility of metoprolol succinate increases [...] Read more.

The solubilities of metoprolol succinate (a cardioselective β1 adrenergic receptor) in methanol, ethanol, n-propanol, isopropanol, n-butanol, ethyl acetate, and acetone were measured at temperatures ranging from (278.2 to 318.2) K using a solid–liquid equilibrium method. The solubility of metoprolol succinate increases with increasing temperature. At a fixed temperature, the solubility decreases in the order methanol > ethanol > n-butanol > n-propanol > isopropanol > acetone > ethyl acetate. The enthalpy of fusion and the melting point of metoprolol succinate were determined by differential scanning calorimetry. The thermodynamic properties of the dissolution process, determined by a van’t Hoff analysis, have been obtained and are discussed. The modified Apelblat equation, Wilson model, and non-random two-liquid (NRTL) model were employed to correlate the solubilities of metoprolol succinate in different solvents. Finally, a quantitative structure–property relationship (QSPR) study of physical properties of solvents and density functional theory simulations of hydrogen-bonding structure were carried out to give the explanation for the sequence of solubility in alcohols. The density functional theory (DFT) calculations well illustrated that the solubility of metoprolol succinate in various alcohols can be mainly attributed to the intra- and intermolecular hydrogen bonds in metoprolol succinate-solvent complexes. Full article

(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2018)

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10 pages, 2397 KiB

Open AccessCommunication

Molecular Recognition via Hydrogen Bonding in Supramolecular Complexes: A Fourier Transform Infrared Spectroscopy Study

by Alfonso Martinez-Felipe, Fraser Brebner, Daniel Zaton, Alberto Concellon, Sara Ahmadi, Milagros Piñol and Luis Oriol

Molecules 2018, 23(9), 2278; https://doi.org/10.3390/molecules23092278 - 6 Sep 2018

Cited by 38 | Viewed by 5770

Abstract

We assess the assembly of supramolecular complexes by hydrogen bonding between azocompounds and a diacylaminopyridine monomer by temperature-dependent Fourier transform infrared spectroscopy (FT-IR) and density functional theory (DFT) calculations. The electronic delocalisation in the supramolecular rings formed by multiple hydrogen bonds stabilises the [...] Read more.

We assess the assembly of supramolecular complexes by hydrogen bonding between azocompounds and a diacylaminopyridine monomer by temperature-dependent Fourier transform infrared spectroscopy (FT-IR) and density functional theory (DFT) calculations. The electronic delocalisation in the supramolecular rings formed by multiple hydrogen bonds stabilises the complexes, which coexist with dimeric species in temperature-dependent equilibria. We show how the application of readily available molecular modelling and spectroscopic techniques can predict the stability of new supramolecular entities coexisting in equilibria, ultimately assessing the success of molecular recognition. Full article

(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2018)

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10 pages, 2390 KiB

Open AccessArticle

DFT Simulations of the Vibrational Spectrum and Hydrogen Bonds of Ice XIV

by Kai Zhang, Peng Zhang, Ze-Ren Wang, Xu-Liang Zhu, Ying-Bo Lu, Cheng-Bo Guan and Yanhui Li

Molecules 2018, 23(7), 1781; https://doi.org/10.3390/molecules23071781 - 19 Jul 2018

Cited by 16 | Viewed by 5493

Abstract

It is always a difficult task to assign the peaks recorded from a vibrational spectrum. Herein, we explored a new pathway of density functional theory (DFT) simulation to present three kinds of spectra of ice XIV that can be referenced as inelastic neutron [...] Read more.

It is always a difficult task to assign the peaks recorded from a vibrational spectrum. Herein, we explored a new pathway of density functional theory (DFT) simulation to present three kinds of spectra of ice XIV that can be referenced as inelastic neutron scattering (INS), infrared (IR), and Raman experimental spectrum. The INS spectrum is proportional to the phonon density of states (PDOS) while the photon scattering signals reflect the normal vibration frequencies near the Brillouin zone (BZ) center. Based on good agreements with the experimental data, we identified the relative frequency and made scientific assignments through normal vibration modes analysis. The two hydrogen bond (H-bond) peaks among the ice phases from INS were discussed and the dynamic process of the H-bond vibrations was found to be classified into two basic modes. We deduced that two H-bond modes are a general rule among the ice family and more studies are ongoing to investigate this subject. Full article

(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2018)

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