scholarly journals HIGH-RESOLUTION GAS PHASE THz SPECTROSCOPY OF THE CATECHOL LOW FREQUENCY MODES INVOLVING AN INTRAMOLECULAR HYDROGEN BOND

2021 ◽  
Author(s):  
Jonas Bruckhuisen ◽  
Arnaud Cuisset ◽  
Marie-Aline Martin-Drumel ◽  
Manuel Goubet ◽  
Thi Tran ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
High Resolution ◽  
Gas Phase ◽  
Intramolecular Hydrogen Bond ◽  
Low Frequency ◽  
Thz Spectroscopy ◽  
Intramolecular Hydrogen

Theoretical calculations of intramolecular hydrogen bond of the 2-Amino-2, 4, 6-cycloheptatrien-1-one in the gas phase and solution: Substituent effects and their positions

2016 ◽  
Vol 15 (07) ◽  
pp. 1650063 ◽  
Author(s):  
Narges Khatoon Attaran Toosy ◽  
Heidar Raissi ◽  
Maryam Zaboli
Keyword(s):  
Hydrogen Bond ◽  
Gas Phase ◽  
Intramolecular Hydrogen Bond ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Substituent Effects ◽  
Dft Method ◽  
Basis Set ◽  
Parent Molecule ◽  
Intramolecular Hydrogen

The density functional theory (DFT) method with 6-311[Formula: see text]G[Formula: see text] basis set has been used to calculate the intramolecular hydrogen bond, molecular structure, vibrational frequencies, nuclear quadrupole resonance (NQR) parameters, 1HNMR, and resonance parameters of 2-Amino-2, 4, 6-cycloheptatrien-1-one (2-amino tropone) and its 18 derivatives in 5 positions. The natural bonding orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses have been studied. The strongest and weakest hydrogen bonds exist for NO2 substituent in R3 position and OH in R7 position, respectively. In general, the substituted systems in position 3 indicate the stronger hydrogen bond in comparison with the parent molecule (R[Formula: see text]H), while, it is comparatively weaker for position 5. The energy of the N-H[Formula: see text]O interaction is found to be medium in strength ([Formula: see text][Formula: see text]kJ mol[Formula: see text] to [Formula: see text][Formula: see text]kJ mol[Formula: see text]). The low [Formula: see text], positive [Formula: see text] values and [Formula: see text] show that the nature of O [Formula: see text] H bonding is electrostatic. Also, our theoretical results show that the hydrogen bond strength in solution phase and the first singlet excited state is weaker in comparison with the gas phase ground state.

Effect of the intramolecular hydrogen bond in the active metabolite analogs of leflunomide for blocking the Plasmodium falciparum dihydroorotate dehydrogenase enzyme: QTAIM, NBO, and docking study

2020 ◽  
Vol 16 ◽  
Author(s):  
Reihaneh Heidarian ◽  
Mansoureh Zahedi-Tabrizi
Keyword(s):  
Hydrogen Bond ◽  
Plasmodium Falciparum ◽  
Molecular Orbital ◽  
Intramolecular Hydrogen Bond ◽  
Active Metabolite ◽  
Chemical Hardness ◽  
Dihydroorotate Dehydrogenase ◽  
Molecular Orbital Analysis ◽  
Intramolecular Hydrogen ◽  
Orbital Analysis

: Leflunomide (LFM) and its active metabolite, teriflunomide (TFM), have drawn a lot of attention for their anticancer activities, treatment of rheumatoid arthritis and malaria due to their capability to inhibit dihydroorotate dehydrogenase (DHODH) and Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) enzyme. In this investigation, the strength of intramolecular hydrogen bond (IHB) in five analogs of TFM (ATFM) has been analyzed employing density functional theory (DFT) using B3LYP/6-311++G (d, p) level and molecular orbital analysis in the gas phase and water solution. A detailed electronic structure study has been performed using the quantum theory of atoms in molecules (QTAIM) and the hydrogen bond energies (EHB) of stable conformer obtained in the range of 76-97 kJ/mol, as a medium hydrogen bond. The effect of substitution on the IHB nature has been studied by natural bond orbital analysis (NBO). 1H NMR calculations show an upward trend in the proton chemical shift of the enolic proton in the chelated ring (14.5 to 15.7ppm) by increasing the IHB strength. All the calculations confirmed the strongest IHB in 5-F-ATFM and the weakest IHB in 2-F-ATFM. Molecular orbital analysis, including the HOMO-LUMO gap and chemical hardness, was performed to compare the reactivity of inhibitors. Finally, molecular docking analysis was carried out to identify the potency of inhibition of these compounds against PfDHODH enzyme.

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