scholarly journals Barbituric Acid Tautomers: DFT Computations of Keto-Enol Conversions, Frontier Molecular Orbitals and Quadrupole Coupling Constants

2021 ◽  
Vol 12 (1) ◽  
pp. 244-252
Keyword(s):  
Density Functional ◽  
Barbituric Acid ◽  
Molecular Orbitals ◽  
Coupling Constants ◽  
Atomic Scale ◽  
Model Systems ◽  
Frontier Molecular Orbitals ◽  
Hydrogen Atoms ◽  
Dft Computations ◽  
Quadrupole Coupling

In this work, density functional theory (DFT) computations were performed to investigate tautomeric formation processes of barbituric acid (BA). Ten tautomers were totally investigated for the purpose based on the movement of hydrogen atoms among nitrogen and oxygen atoms providing one pure keto form (BA1) and nine other keto-enol forms. The structures were optimized, and BA1 was found to be the most stable one, and both BA3 and BA7 were found to be the most unstable ones. The point was that the ring structure was broken for both BA3 and BA7, but the structure's stability was still approved. Indeed, such serious tautomeric conversion with breaking the structure warns for using such BA bio-organic molecules for further applications, especially in pharmacy-related ones, in which side effects or byproduct synthesis might appear. Further analyses of frontier molecular orbitals features indicated the effects of such tautomerism processes on all model systems, in which more details were obtained by atomic-scale quadrupole coupling constant (Qcc). All obtained results approved significant changes of tautomers regarding molecular and atomic scale features with more or less significant effects regarding the original BA1 reference model.

Investigating Functionalization Impacts on Structural Features of Barbituric Acid Derivatives: DFT Approach

2021 ◽  
pp. 1-9
Author(s):  
Narjes Hajali ◽  
Afshin Taghva Manesh ◽  
Ahmad Seif
Keyword(s):  
Density Functional ◽  
Barbituric Acid ◽  
Minimum Energy ◽  
Structural Features ◽  
Coupling Constants ◽  
Atomic Scale ◽  
Functional Theory ◽  
Quadrupole Coupling ◽  
Homo And Lumo ◽  
Characteristic Features

Density functional theory (DFT) calculations were performed to investigate electronic and structural properties of barbituric acid (BA) and sixtheen of its derivatives to show impacts of structural functionalization on the features of parent BA. The models were optimized and the minimum energy structures were confirmed by frequency calculations. Molecular and atomic descriptors were evaluated for the optimized models, in which the results of formation binding strength and molecular orbital features indicated significance of such functionalization processes on the observed properties. The highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) and their related parameters all indicated magnitudes of changes from one molecule to another one. Furthermore, atomic scale quadrupole coupling constants (Cq) were evaluated for the nitrogen and oxygen atoms of BA compounds showing significance of structural functionalization impacts on the atomic properties of parent BA. As a consequence, such structural analyses of BA compounds could show their characteristic features for further developments especially for their efficient pharmaceutical applications.

Structural analysis of dexrazoxane: Exploring tautomeric conformations

2021 ◽  
pp. 1-8
Author(s):  
Farnoosh Behboodyzad ◽  
Tahereh Mohseniabbasabadi ◽  
Nahal Ghanemnia ◽  
Ebrahim Balali
Keyword(s):  
Structural Analysis ◽  
Density Functional ◽  
Distribution Patterns ◽  
Heterocyclic Ring ◽  
Coupling Constants ◽  
Original Structure ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Quadrupole Coupling

Structural analysis of dexrazoxane, as a cardioprotective agent, was done in this work by exploring formations of tautomeric conformations and investigating the corresponding effects. Density functional theory (DFT) calculations were performed to optimize the structures to evaluate their molecular and atomic descriptors. In addition to the original structure of dexrazoxane, eight tautomers were obtained with lower stability than the original compound. Movements of two hydrogen atoms in between nitrogen and oxygen atoms of heterocyclic ring put such significant effects. Moreover, electronic molecular orbital features showed effects of such tautomerism processes on distribution patterns and surfaces, in which evaluating the quadrupole coupling constants helped to show the role of atomic sites for resulting the features. As a consequence, the results indicated that the tautomeric formations could significantly change the features of dexrazoxane reminding the importance of carful medication of this drug for patients.

Influence of C-Doping on the B-11 and N-14 Quadrupole Coupling Constants in Boron-Nitride Nanotubes: A DFT Study

2007 ◽  
Vol 62 (1-2) ◽  
pp. 56-60 ◽  
Author(s):  
Mahmoud Mirzaei ◽  
Nasser L. Hadipour ◽  
Mohammad Reza Abolhassani
Keyword(s):  
Boron Nitride ◽  
Density Functional ◽  
Computational Study ◽  
Boron Nitride Nanotubes ◽  
Coupling Constants ◽  
Carbon Doping ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Quadrupole Coupling ◽  
C Doping

A computational study at the level of density functional theory (DFT) was carried out to investigate the influence of carbon doping (C-doping) on the 11B and 14N quadrupole coupling constants (CQ) in the (6,0) single-walled boron-nitride nanotube (BNNT). To this aim, a 10 Å length of BNNT consisting of 24 B atoms and 24 N atoms was selected where the end atoms are capped by hydrogen atoms. To follow the purpose, six C atoms were doped instead of three B and three N atoms as a central ring in the surface of the C-doped BNNT. The calculated CQ values for both optimized BNNT systems, raw and C-doped, reveal different electrostatic environments in the mentioned systems. It was also demonstrated that the end nuclei have the largest CQ values in both considered BNNT systems.

Non-Covalent Functionalisation of C30 Fullerene by Pyrrole-n-Carboxylic Acid (n=2, 3): Density Functional Theory Studies

2017 ◽  
Vol 73 (1) ◽  
pp. 51-56
Author(s):  
Kun Harismah ◽  
Mahmoud Mirzaei ◽  
Nahid Ghasemi ◽  
Mohammad Nejati
Keyword(s):  
Density Functional Theory ◽  
Carboxylic Acid ◽  
Density Functional ◽  
Spherical Shape ◽  
Density Functional Theory Calculations ◽  
Coupling Constants ◽  
Atomic Scale ◽  
Functional Theory ◽  
Quadrupole Coupling ◽  
Non Covalent Interactions

AbstractFor functionalisation of a representative C30 fullerene nanostructure by pyrrole-n-carboxylic acid (PnCA; n=2, 3) their stabilities and properties were investigated based on density functional theory calculations. Parallel calculations were also done for C60 fullerene as evidence for comparing the results. Non-covalent interactions are considered to make the functionalised structures. In contrast with the spherical shape of C60, the shape of C30 fullerene is elliptical; therefore, the functionalisation processes were done for both axial and equatorial elliptical positions (AC30 and EC30). The results indicated that both the positions of C30 have almost equivalent chances to be functionalised by PnCA; but functionalisation by P2CA is slightly more favourable than P3CA, either for C60. The illustrated molecular orbitals’ distributions indicated that the direction of charge transfer could be considered from PnCA counterparts to fullerene counterparts. The molecular properties indicated more reactivity for C30 than for C60 fullerene. Finally, the atomic scale quadrupole coupling constants indicated different roles for N and O atoms of PnCA in the functionalised models.

scholarly journals Structural Analyses of Vanillin Derivative Compounds and their Molecular Docking with MPro and RdRp Enzymes of COVID-19

2021 ◽  
Vol 12 (2) ◽  
pp. 1660-1669
Keyword(s):  
Molecular Docking ◽  
Density Functional ◽  
Md Simulations ◽  
Aldehyde Group ◽  
Coupling Constants ◽  
Atomic Scale ◽  
Main Protease ◽  
Quadrupole Coupling ◽  
New Compounds ◽  
The Impact

In this work, structural analyses of vanillin (Vanl) and eleven of its derivatives based on the modification of the aldehyde group were investigated using density functional theory (DFT) calculations. In this regard, molecular orbital features and atomic-scale quadrupole coupling constants were evaluated for geometrically optimized structures to see the impact of structural modification on the whole structure. The results indicated that the main impact of such modification was significant only for the modification region, whereas the impact on the rest of the structure was almost negligible. However, electronic features indicated a different tendency for Vanl derivatives for involving in interaction with enzymatic targets. Because of the importance of innovating medication for COVID-19, main protease (MPro) and RNA-dependent RNA polymerase (RdRp) were chosen for the enzymatic target of Vanl ligands for the formation of ligand-target complexes through performing molecular docking (MD) simulations. The results indicated that among the complexes, Vanl 9 (–NHNH2) and 11 (–CH2Cl) could work as the best ligands for interacting with each of RdRp and MPro, respectively. Consequently, optimization of Vanl derivatives could help innovate new compounds for the possible medication of the COVID-19 pandemic.

Density Functional Theory Studies of Bonding in Complexes H3N···XY of Ammonia and Dihalogen Molecules: A Comparison with Experimental Results from Rotational Spectroscopy

2002 ◽  
Vol 57 (6-7) ◽  
pp. 537-543 ◽  
Author(s):  
O. Kh. Poleshchuk ◽  
A. C. Legona
Keyword(s):  
Density Functional ◽  
Natural Bond Orbital ◽  
Coupling Constants ◽  
Rotational Spectroscopy ◽  
Charge Redistribution ◽  
Functional Theory ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Experimental Values

The electron density and nuclear quadrupole coupling constants (NQCC) of the H3N...XY (n a type in Mulliken notation) complexes, (X, Y = F, Cl, Br and I), are analyzed with the aid of density functional calculations. To demonstrate the quality of the calculations, various bond lengths and NQCCs obtained by using the hybrid Becke-Lee-Perdew-Yang functional are compared with the corresponding experimental values determined from rotational spectroscopy. An analysis of the NQCC values and various quantities derived fromthe natural bond orbital approach reveals that the molecular interaction is mainly electrostatic, with probably only a small extent of intermolecular electric charge redistribution on complex formation

Sign in / Sign up

Export Citation Format

Share Document