Thiadiazole-2-Thiol-5-Thione and 2,5-Dimercapto-1,3,4-Thiadiazol Tautomerism, Conformational Stability, Vibrational Assignments, Inhibitor Efficiency and Quantum Chemical Calculations

AbstractRaman (3700–100 cm−1) and infrared (4000–400 cm−1) spectra of 2,5-Dimercapto-1,3,4-thiadiazol (DMTD) were recorded in the solid phase. Six structures (1–6) were initially proposed for DMTD as a result of thiol-thione tautomerism and internal rotation(s) of thiol group(s) around the C–S bond. Quantum chemical calculations were carried out for an isolated molecule (1–6) using density functional theory (B3LYP) and ab initio MP2(full) methods utilizing 6-31G(d) and 6-311++G(d,p) basis sets which favor thiol-thione tautomerism (structure 4). Relaxed potential energy surface scans of structure 4 revealed an additional conformer (the thiol group is out-of-plane, structure 7) using the aforementioned methods at 6-311++G(d,p) basis set. For additional verification, plane-wave solid state calculations were carried out at PW91 and PBEsol came out in favor of conformer 7. This is in agreement with the computed/observed SH in-plane bending of S-7 (959/941 cm−1) rather than the one estimated at (880 cm−1) for S-4. Moreover, the observed split IR/Raman bands were found consistent with solid state calculated frequencies of S-7 assuming two molecules per unit cell bonded via H-bonding intermolecular interactions. Aided by vibrational frequency calculations, normal coordinate analysis, force constants and potential energy distributions (PEDs), a complete vibrational assignment for the observed IR and Raman bands is proposed herein. Furthermore, we have estimated the frontier molecular orbitals and atomic charges to account for the corrosion inhibition efficiency of DMTD along with its binding sites to the metal surface. Our results are discussed herein and compared to similar molecules whenever appropriate.

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Solid-state linear polarized IR-spectroscopy of croconic and rhodizonic acids

Open Chemistry ◽

10.2478/s11532-008-0028-1 ◽

2008 ◽

Vol 6 (3) ◽

pp. 393-399 ◽

Cited By ~ 5

Author(s):

Tsonko Kolev ◽

Bojidarka Koleva ◽

Michael Spiteller

Keyword(s):

Solid State ◽

Ir Spectroscopy ◽

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Vibrational Analysis ◽

Basis Set ◽

Experimental Ir ◽

Vibrational Assignments ◽

Neutral Compounds ◽

Polarized Ir Spectroscopy

AbstractThe applications of linear-polarized IR-spectroscopy to oriented colloid suspensions in a nematic host are demonstrated with croconic and rhodizonic acids. The experimental IR vibrational assignments of the solid-state of both neutral compounds are presented. Assignments are supported by theoretical quantum chemical calculations and vibrational analysis at the DFT level of theoretical approximation with the 6-311++G** basis set.

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DFT Studies and Quantum Chemical Calculations of Benzoyl Thiourea Derivatives Linked with Morpholine and Piperidine for the Evaluation of Antifungal Activity

Current Physical Chemistry ◽

10.2174/1877946812666220111141742 ◽

2022 ◽

Vol 12 ◽

Author(s):

Rameshwar K. Dongare ◽

Shaukatali N. Inamdar ◽

Radhakrishnan M. Tigote

Keyword(s):

Antifungal Activity ◽

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Density Functional ◽

Basis Set ◽

Functional Study ◽

Chemical Parameters ◽

Thiourea Derivatives ◽

Quantum Chemical Parameters ◽

B3lyp Method

Herein, we report the density functional study of benzoyl thiourea derivatives linked to morpholine and piperidine to evaluate their antifungal activity. Overall six compounds BTP 1-3 and BTM 4-6 were optimized with DFT using the B3LYP method with 6-31G(d,p) basis set. The molecular geometry, bond lengths, bond angles, atomic charges and HOMO-LUMO energy gap have been investigated. The structural parameters have been compared with the reported experimental results and structure- antifungal activity relationship is explored in details. The calculated results from DFT were discussed using all Quantum chemical parameters of the compounds. Introduction: Benzoyl thiourea derivatives linked with morpholine and piperidine were reported to have good antifungal activity. Objective: To find the correlations between the quantum chemical calculations and the antifungal activity for the benzoyl thiourea derivatives linked with morpholine and piperidine. Method: Optimization was carried out with DFT using B3LYP method utilizing 6-31G(d,p) basis set. Results: A good correlation between the quantum chemical calculations and the antifungal activity for the benzoyl thiourea derivatives linked with morpholine and piperidine was found. Conclusion: The DFT study of benzoyl thiourea derivatives linked to morpholine and piperidine was evaluated for their antifungal activity and it showed good correlations of activity with the quantum chemical parameters.

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Molecular and Electronic Structure of 1-Naphtol : Ab Initio Molecular Orbital and Density Functional Study

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.110-116.1862 ◽

2011 ◽

Vol 110-116 ◽

pp. 1862-1869

Author(s):

G. Raja ◽

K. Saravanan ◽

S. Sivakumar

Keyword(s):

Ab Initio ◽

Quantum Chemical Calculations ◽

Raman Spectra ◽

Quantum Chemical ◽

Density Functional ◽

Computational Method ◽

Basis Set ◽

Mode Analysis ◽

Functional Study ◽

Infrared And Raman Spectra

The molecular vibrations of 1-Naphtol were investigated in polycrystalline sample, at room temperature, by FT- IR and FT-Raman spectroscopy. In parallel, ab initio and various density functional (DFT) methods were used to determine the geometrical, energetic and vibrational characteristics of 1-Naphtol . On the basis of B3LYP/6-31G* and B3LYP/6-311+G** methods and basis set combinations, a xnormal mode analysis was performed to assign the various fundamental frequencies according to the total energy distribution (TED). The vibrational spectra were interpreted, with the aid of normal coordinate analysis based on a scaled quantum mechanical force field. The Infrared and Raman spectra were also predicted from the calculated intensities. Comparison of simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. Simulation of Infrared and Raman spectra, utilizing the results of these calculations led to excellent overall agreement with observed spectral patterns. The investigation is performed using quantum chemical calculations conducted by means of the Gaussian 98W and Guassview set of programs. Further, density functional theory (DFT) combined with quantum chemical calculations to determine the first-order hyperpolarizability.

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An experimental and theoretical study on siderol isolated from Sideritis species

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc2010119 ◽

2011 ◽

Vol 76 (2) ◽

pp. 95-114 ◽

Cited By ~ 8

Author(s):

Akin Azizoglu ◽

Zuleyha Özer ◽

Turgut Kiliç

Keyword(s):

Density Functional ◽

Solid Phase ◽

Basis Set ◽

Geometrical Parameters ◽

Functional Theory ◽

Vibrational Assignments ◽

Aerial Parts ◽

Functional Methods ◽

The Fourier Transform ◽

Nmr Properties

The Fourier transform infrared (FTIR) spectrum of siderol, extracted from the aerial parts of Sideritis Gülendamii, has been measured in the range 4000–400 cm–1. Vibrational assignments and analyses of the fundamental modes of siderol were performed using the observed FTIR data recorded in the solid phase. The vibrational frequencies determined experimentally are compared with those obtained theoretically from density functional theory (DFT) and Hartee–Fock (HF) calculations. Optimized geometrical parameters of the title compound are in agreement with similar reported structures. The 1H and 13C NMR spectra of siderol have also been calculated by means of DFT and HF methods. The comparison between the experimental and the theoretical results indicates that density functional methods, B3LYP and MPW1PW91 with 6-31G(d) basis set, are able to provide satisfactory results for predicting NMR properties. On the basis of vibrational analyses, the thermodynamic properties of the title molecule have also been computed.

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Synthesis, Characterization and TheoreticalStudies of Nand#39;-(4-methoxybenzylidene)benzenesulfonohydrazide

Journal of the chemical society of pakistan ◽

10.52568/000568 ◽

2021 ◽

Vol 43 (2) ◽

pp. 212-212

Author(s):

H G zin Aslan and L tfiye Aydin H G zin Aslan and L tfiye Aydin

Keyword(s):

Potential Energy ◽

Gas Phase ◽

Vibrational Spectra ◽

Potential Energy Surfaces ◽

Solid Phase ◽

Nbo Analysis ◽

Basis Set ◽

Basis Sets ◽

Stable Conformer ◽

Energy Surfaces

Nand#39;-(4-methoxybenzylidene)benzenesulfonohydrazide was synthesized and elemental analysis was conducted; IR, Raman, 1H, and 13C NMR spectral data were recorded. The potential energy surfaces (PES) of the Nand#39;-(4-methoxybenzylidene)benzenesulfonohydrazide molecule were obtained by selected degree of torsional freedom, which varied from 0o to 360and#186; in 4and#186; increments. The conformers were optimized by using a (DFT/B3LYP/6-31G(d,p)) basis set in the gas phase. The eleven conformers in the gas phase of the obtained molecule were determined and the most stable conformer (conformer 1) was re-optimized by three different basis sets of 6-31G(d,p), 6-311G(d,p), and LanL2Dz. HOMO-LUMO analyses were performed. NBO analysis was performed to describe the around of intramolecular charge transfer. The vibrational spectra were measured in solid phase IR and detailed analysis of the vibrational spectra of conformer 1 was done; all the bands of the spectra were interpreted by the use of the potential energy distributions (PED) and the molecular electrostatic potential (MEP) was plotted.

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Oxane dendrimers of tetravalent elements as models for their dioxide polymorphs

Surface ◽

10.15407/surface.2021.13.003 ◽

2021 ◽

Vol 13(28) ◽

pp. 3-14

Author(s):

A.G. Grebenyuk ◽

Keyword(s):

Quantum Chemical ◽

Density Functional ◽

Tin Dioxide ◽

Basis Set ◽

Basis Sets ◽

Hydroxyl Groups ◽

High Symmetry ◽

Molecular Models ◽

Basis Set Superposition Error ◽

Theoretical Approaches

Oxides of tetravalent elements are well known to have a lot of crystalline modifications. For example, most of silica polymorphs are characterized by tetrahedral coordination environment of silicon atoms. On the contrary, crystals of stishovite and of some silicate minerals have their silicon atoms in octahedral coordination spheres. It has been found experimentally that the phase transitions between silica polymorphs accompanied by a rearrangement of silica-oxygen tetrahedrons into octahedra require an energy income (preference energy) of 54 kJ/mol. When increasing the atomic mass of the oxide forming element, the former decreases extremely and for tin dioxide is equal to -59 kJ/mol. These values can be reproduced in a theoretical way, within the frameworks of modern quantum chemical methods and periodic models. High disperse silica nanoparticles (as well as those for other oxides) have only the nearest order of atomic stationing, so that theoretical approaches developed for crystals cannot be applied to small particles. These particles can be transformed into stishovite form under hydrothermal conditions. Such a process can be simulated within cluster approximation by use of molecular models. This work is devoted to quantum chemical simulation of formation of the fragments with hexa-coordinated atoms of silicon and of its analogs in the structure of oxane dendrimers. A row of high symmetry models was examined containing two, three, five, and seventeen atoms of silicon and of germanium, titanium and tin, terminated with hydroxyl groups. These structures can be rearranged into another ones including oxide forming atoms with elevated (equal to 5 or 6) coordination number, so mimicking the rutile-like structure. Such models let it possible to fulfill the procedure of transformation without rupturing siloxane bonds, so remaining within a deformation approach. Another advantage is the exclusion of the basis set superposition error due to use of molecular models of the same total formula for all the coordination states. All calculations were carried out by Hartree-Fock and density functional theory methods with the all-electron (3-21G*) and valent (SBKJC) basis sets by means of the GAMESS program. Models of various size have been examined, in particular, disiloxane (HO)3Si-O-Si(OH)3 witch can be transformed into a self-coordinated form where one of silicon atoms becomes a five-coordinated; trisiloxane (HO)3Si-O-Si(OH)2-O-Si(OH)3 can be rearranged into symmetric isomer with one hexa-coordinated silicon atom. Pentasiloxane with neo-structure of [(HO)3Si-O]4Si forms three coordination structures, the most stable of them mimicking the stishovite crystal; it contains one 6-coordinated and two 5-coordinated silicon atoms. Siloxane containing 17 silicon atoms has a super-neo-structure of {[(HO)3Si-O]3Si-O}4Si; it includes seven six-coordinated and four five-coordinated silicon atoms. Relative models for silicon analogs have been also examined. When analyzing a dependence of the energy differences between open and coordinated oxane structures on the number of atoms of the oxide forming element in the cluster, one can jump to the conclusion that the specific value of this characteristic monotonously decreases with the increase in the number of atoms of the molecular model, so becoming close to the experimental data.

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Dative versus electron-sharing bonding in N-oxides and phosphane oxides R3EO and relative energies of the R2EOR isomers (E = N, P; R = H, F, Cl, Me, Ph). A theoretical study

Physical Chemistry Chemical Physics ◽

10.1039/c8cp00951a ◽

2018 ◽

Vol 20 (17) ◽

pp. 11856-11866 ◽

Cited By ~ 12

Author(s):

Tao Yang ◽

Diego M. Andrada ◽

Gernot Frenking

Keyword(s):

Density Functional Theory ◽

Ab Initio ◽

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Density Functional ◽

Theoretical Study ◽

Basis Sets ◽

Functional Theory

Quantum chemical calculations using ab initio methods at the CCSD(T)/def2-TZVPP level and density functional theory using BP86 and M06-2X functionals in conjunction with def2-TZVPP basis sets have been carried out on the title molecules.

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DFT study of low-energy electron interaction with pyridine, pyrazine and their halo derivatives

The European Physical Journal D ◽

10.1140/epjd/s10053-021-00137-0 ◽

2021 ◽

Vol 75 (4) ◽

Author(s):

Natalia Tańska

Keyword(s):

Potential Energy ◽

Density Functional ◽

Low Energy ◽

Energy Electron ◽

Potential Energy Curves ◽

Basis Set ◽

Basis Sets ◽

Electron Interaction ◽

Electron Affinities ◽

Low Energy Electron

Abstract In this work, the density functional theory with B3LYP hybrid functional was employed to calculate quantities useful for estimating the behavior of pyridine, pyrazine and their derivatives monosubstituted with Cl or Br atom, when exposed to low-energy electron impact. Vertical electron affinities obtained in several Pople basis sets and in aug-cc-pVTZ basis set are reported. Although some of the investigated molecules do not form stable anions, the results are in a satisfactory agreement with the available, albeit sparse experimental data, if the diffuse functions are included in calculations. It was found that the 6-31+G* basis is sufficient and its further enlargement does not significantly change the results. At this level of theory, potential energy curves, supported by enthalpies of dissociation to the neutral and anion fragment, were also determined for the description of the dissociative electron attachment. According to B3LYP, the potential energy curves of the halogen bond are almost repulsive in halopyridines, whereas halopyrazine anions require small activation energy for dissociation. Vertical electron affinities, enthalpies and equilibrium C-X distances (X=H, Cl, Br) were also calculated using Møller-Plesset second-order perturbation theory. Graphic Abstract

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DFT and Bader's AIM analysis of 2,5-,diphenyl-1,3,4-oxadizole molecule: A organic light emitting diode (OLED)

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633615500388 ◽

2015 ◽

Vol 14 (05) ◽

pp. 1550038 ◽

Cited By ~ 3

Author(s):

P. Srinivasan ◽

A. David Stephen

Keyword(s):

Electron Density ◽

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Density Functional ◽

Light Emitting Diode ◽

Basis Sets ◽

Bond Critical Point ◽

Light Emitting ◽

Organic Light Emitting Diode ◽

Organic Light

The electron density and conductivity studies of 2,5-diphenyl-1,3,4-oxadizole organic light emitting diode (OLED) based molecule have been calculated from the quantum chemical calculations and combined with the Bader's AIM theory. Density functional theory calculations with B3LYP/aug-cc-PVDZ basis sets was used to determine ground state gas space molecular geometries (bond lengths and bond angles), electron density and bonding features of this molecule. The electron densities at the bond critical point (BCP) of aromatic Car–Car bonds are much stronger than the other bonds in the molecule. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The HOMO–LUMO gap calculated from quantum chemical calculations has been compared with the value calculated from the density of states. The negative electrostatic potential (ESP) is concentrated solely around the N atoms, whereas in the rest of the region a positive ESP to dominate.

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The Nature of Chemisorbed CO2 in Zeolite A

10.26434/chemrxiv.7422815 ◽

2019 ◽

Author(s):

Przemyslaw Rzepka ◽

Zoltán Bacsik ◽

Andrew J. Pell ◽

Niklas Hedin ◽

Aleksander Jaworski

Keyword(s):

Solid State ◽

Ir Spectroscopy ◽

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Surface Coverage ◽

Gas Mixtures ◽

Mas Nmr ◽

Significant Fraction ◽

Zeolite A

Formation of CO32- and HCO3- species without participation of the framework oxygen atoms upon chemisorption of CO2 in zeolite |Na12|-A is revealed. The transfer of O and H atoms is very likely to have proceeded via the involvement of residual H2O or acid groups. A combined study by solid-state 13C MAS NMR, quantum chemical calculations, and in situ IR spectroscopy showed that the chemisorption mainly occurred by the formation of HCO3-. However, at a low surface coverage of physisorbed and acidic CO2, a significant fraction of the HCO3- was deprotonated and transformed into CO32-. We expect that similar chemisorption of CO2 would occur for low-silica zeolites and other basic silicates of interest for the capture of CO2 from gas mixtures.

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