Intramolecular hydrogen-bonding effects on structural and electronic properties of pyrrole-furan derivatives: a density functional calculation

2021 ◽  
Vol 53 (5) ◽  
Author(s):  
Sutida Asawamongkolsiri ◽  
Nuttaporn Janprapa ◽  
Viwat Vchirawongkwin ◽  
Chinapong Kritayakornupong
Keyword(s):  
Hydrogen Bonding ◽  
Electronic Properties ◽  
Density Functional ◽  
Intramolecular Hydrogen Bonding ◽  
Density Functional Calculation ◽  
Furan Derivatives ◽  
Structural And Electronic Properties ◽  
Intramolecular Hydrogen

scholarly journals NMR of Natural Products as Potential Drugs

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3763
Author(s):  
Poul Erik Hansen
Keyword(s):  
Natural Products ◽  
Hydrogen Bonding ◽  
Density Functional ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Density Functional Theory Calculations ◽  
Intramolecular Hydrogen Bonding ◽  
Chemical Equilibria ◽  
Nmr Techniques ◽  
Intramolecular Hydrogen

This review outlines methods to investigate the structure of natural products with emphasis on intramolecular hydrogen bonding, tautomerism and ionic structures using NMR techniques. The focus is on 1H chemical shifts, isotope effects on chemical shifts and diffusion ordered spectroscopy. In addition, density functional theory calculations are performed to support NMR results. The review demonstrates how hydrogen bonding may lead to specific structures and how chemical equilibria, as well as tautomeric equilibria and ionic structures, can be detected. All these features are important for biological activity and a prerequisite for correct docking experiments and future use as drugs.

Switching On/Off the Intramolecular Hydrogen Bonding of 2-Methoxyphenol Conformers: An NMR Study

2020 ◽  
Vol 73 (3) ◽  
pp. 222
Author(s):  
Frederick Backler ◽  
Feng Wang
Keyword(s):  
Hydrogen Bonding ◽  
Chemical Shift ◽  
1H Nmr ◽  
Density Functional ◽  
Point Group ◽  
Decomposition Analysis ◽  
Intramolecular Hydrogen Bonding ◽  
Group Symmetry ◽  
Energy Decomposition Analysis ◽  
Intramolecular Hydrogen

Intramolecular hydrogen bonding of 2-methoxyphenol (2-MP, guaiacol) is studied using NMR spectroscopy combined with quantum mechanical density functional theory (DFT) calculations. The hydrogen bonding of OH⋯O and HO⋯H is switched on in the conformers of anti–syn (AS, 99.64% dominance) and anti–gauche (AG), respectively, with respect to the anti–anti (AA) conformer (without either such hydrogen bonding interactions). It confirms that the 13C and 1H NMR chemical shift of AS dominates the measured NMR spectra, as the AS conformer reproduces the measurements in CDCl3 solvent (RMSD of 1.86ppm for 13C NMR and of 0.27ppm for 1H NMR). The chemical shift of hydroxyl H(1) at 5.66 pm is identified as the fingerprint of the OH(1)⋯OCH3 hydrogen bonding in AS, as it exhibits a significant deshielding from H(1) of AA (4.24ppm) and H(1) of AG (4.38ppm) without such OH(1)⋯OCH3 hydrogen bonding. The AG conformer (C1 point group symmetry) possesses a less strong hydrogen bonding of HO⋯HCH2O, with the methoxyl group out of the aromatic phenol plane. The substituent effect of AG due to the resonance interaction of methoxyl being out of plane in a concentrated solution shifts the ortho- and para-aromatic carbons, C(3)/C(5), of the AG to ~125.05/125.44ppm from the corresponding carbons in AS at 108.81/121.60ppm. The hydrogen bonding exhibits inwards reduction of IR frequency regions of AS and AG from AA. Finally, energy decomposition analysis (EDA) indicates that there is a steric energy of 45.01kcal mol−1 between the AS and AG when different intramolecular hydrogen bonding is switched on.

CONFORMATIONAL PROPERTIES AND INTRAMOLECULAR HYDROGEN BONDING OF 3-AMINO-PROPENESELENAL: AN AB INITIO AND DENSITY FUNCTIONAL THEORY STUDIES

2013 ◽  
Vol 12 (04) ◽  
pp. 1350025 ◽  
Author(s):  
HEIDAR RAISSI ◽  
FARZANEH FARZAD ◽  
SHAHIRA ESLAMDOOST ◽  
FARIBA MOLLANIA
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bonding ◽  
Molecular Orbital ◽  
Continuum Model ◽  
Density Functional ◽  
Intramolecular Hydrogen Bonding ◽  
Stationary Points ◽  
Functional Theory ◽  
Polarized Continuum Model ◽  
Intramolecular Hydrogen

In the present work a conformational analysis of 3-amino-propeneselenal (APS) was performed using several computational methods, including DFT (B3LYP), MP2 and G2MP2. Harmonic vibrational frequencies were estimated at the same levels to confirm the nature of the stationary points found and also to account for the zero point vibrational energy (ZPVE) correction. Two intramolecular hydrogen bonds (HBs) established between the polar groups were identified by the structural geometric parameters. The excited-state properties of intramolecular hydrogen bonding in hydrogen bonded systems have been investigated theoretically using the time dependent density functional theory (TDDFT) method. The influence of the solvent on the stability order of conformers and the strength of intramolecular hydrogen bonding was considered using the polarized continuum model (PCM), the self-consistent isodensity polarized continuum model (SCI-PCM) and the integral equation formalism-polarizable continuum model (IEF-PCM) methods. The "atoms in molecules" theory of Bader was used to analyze critical points and to study the nature of HB in these systems. Natural bond orbital (NBO) analysis was also performed for better understanding the nature of intramolecular interactions. The calculated the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies show that charge transfer occur within the molecule. Further verification of the obtained transition state structures were implemented via intrinsic reaction coordinate (IRC) analysis. Calculations of the 1 H NMR chemical shift at GIAO/B3LYP/6–311++G** level of theory are also presented.

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