Revealing the mechanism of the water autoprotolysis on the basis of Marcus theory and TD-DFT methodology

2021 ◽  
Vol 324 ◽  
pp. 115092
Author(s):  
Antonio García Martínez ◽  
Pedro C. Gómez ◽  
Santiago de la Moya ◽  
Hans-Ullrich Siehl
Keyword(s):  
Marcus Theory ◽  
Td Dft

The Nature of S-N Bonding in Sulfonamides and Related Compounds: Insights into π-Bonding Contributions from Sulfur K-Edge XAS

2020 ◽  
Author(s):  
Tulin Okbinoglu ◽  
Pierre Kennepohl
Keyword(s):  
Density Functional ◽  
Chemical Properties ◽  
Functional Theory ◽  
Rotational Barriers ◽  
Td Dft ◽  
Nitrogen Bonds ◽  
X Ray Absorption ◽  
Related Compounds ◽  
And Chemical Properties

Molecules containing sulfur-nitrogen bonds, like sulfonamides, have long been of interest due to their many uses and chemical properties. Understanding the factors that cause sulfonamide reactivity is important, yet their continues to be controversy regarding the relevance of S-N π bonding in describing these species. In this paper, we use sulfur K-edge x-ray absorption spectroscopy (XAS) in conjunction with density functional theory (DFT) to explore the role of S<sub>3p</sub> contributions to π-bonding in sulfonamides, sulfinamides and sulfenamides. We explore the nature of electron distribution of the sulfur atom and its nearest neighbors and extend the scope to explore the effects on rotational barriers along the sulfur-nitrogen axis. The experimental XAS data together with TD-DFT calculations confirm that sulfonamides, and the other sulfinated amides in this series, have essentially no S-N π bonding involving S<sub>3p</sub> contributions and that electron repulsion and is the dominant force that affect rotational barriers.

The Character of Low-Lying Excited States of Mixed-Ligand Metal Carbonyls. TD-DFT and CASSCF/CASPT2 Study of [W(CO)4L] (L = ethylenediamine, N,N'-dialkyl-1,4-diazabutadiene) and [W(CO)5L] (L = pyridine, 4-cyanopyridine)

2003 ◽  
Vol 68 (1) ◽  
pp. 89-104 ◽  
Author(s):  
Stanislav Záliš ◽  
Antonín Vlček ◽  
Chantal Daniel
Keyword(s):  
Excited States ◽  
Substitution Effect ◽  
Electronic Transitions ◽  
Ligand Field ◽  
Metal Carbonyls ◽  
Electron Density Redistribution ◽  
Time Resolved ◽  
Model Complex ◽  
Td Dft ◽  
Time Resolved Infrared Spectroscopy

This contribution presents the results of the TD-DFT and CASSCF/CASPT2 calculations on [W(CO)4(MeDAB)] (MeDAB = N,N'-dimethyl-1,4-diazabutadiene), [W(CO)4(en)] (en = ethylenediamine), [W(CO)5(py)] (py = pyridine) and [W(CO)5(CNpy)] (CNpy = 4-cyanopyridine) complexes. Contrary to the textbook interpretation, calculations on the model complex [W(CO)4(MeDAB)] and [W(CO)5(CNpy)] show that the lowest W→MeDAB and W→CNpy MLCT excited states are immediately followed in energy by several W→CO MLCT states, instead of ligand-field (LF) states. The lowest-lying excited states of [W(CO)4(en)] system were characterized as W(COeq)2→COax CT excitations, which involve a remarkable electron density redistribution between axial and equatorial CO ligands. [W(CO)5(py)] possesses closely-lying W→CO and W→py MLCT excited states. The calculated energies of these states are sensitive to the computational methodology used and can be easily influenced by a substitution effect. The calculated shifts of [W(CO)4(en)] stretching CO frequencies due to excitation are in agreement with picosecond time-resolved infrared spectroscopy experiments and confirm the occurrence of low-lying M→CO MLCT transitions. No LF electronic transitions were found for either of the complexes studied in the region up to 4 eV.

scholarly journals Exo⇔Endo Isomerism, MEP/DFT, XRD/HSA-Interactions of 2,5-Dimethoxybenzaldehyde: Thermal, 1BNA-Docking, Optical, and TD-DFT Studies

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5970
Author(s):  
Nabil Al-Zaqri ◽  
Mohammed Suleiman ◽  
Anas Al-Ali ◽  
Khaled Alkanad ◽  
Karthik Kumara ◽  
...  
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Structural Parameters ◽  
Population Analysis ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Optical Energy Gap ◽  
Functional Theory ◽  
Reactivity Descriptors ◽  
Td Dft

The exo⇔endo isomerization of 2,5-dimethoxybenzaldehyde was theoretically studied by density functional theory (DFT) to examine its favored conformers via sp2–sp2 single rotation. Both isomers were docked against 1BNA DNA to elucidate their binding ability, and the DFT-computed structural parameters results were matched with the X-ray diffraction (XRD) crystallographic parameters. XRD analysis showed that the exo-isomer was structurally favored and was also considered as the kinetically preferred isomer, while several hydrogen-bonding interactions detected in the crystal lattice by XRD were in good agreement with the Hirshfeld surface analysis calculations. The molecular electrostatic potential, Mulliken and natural population analysis charges, frontier molecular orbitals (HOMO/LUMO), and global reactivity descriptors quantum parameters were also determined at the B3LYP/6-311G(d,p) level of theory. The computed electronic calculations, i.e., TD-SCF/DFT, B3LYP-IR, NMR-DB, and GIAO-NMR, were compared to the experimental UV–Vis., optical energy gap, FTIR, and 1H-NMR, respectively. The thermal behavior of 2,5-dimethoxybenzaldehyde was also evaluated in an open atmosphere by a thermogravimetric–derivative thermogravimetric analysis, indicating its stability up to 95 °C.

scholarly journals One-Pot Microwave-Assisted Synthesis of Water-Soluble Pyran-2,4,5-triol Glucose Amine Schiff Base Derivative: XRD/HSA Interactions, Crystal Structure, Spectral, Thermal and a DFT/TD-DFT

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 117
Author(s):  
Yousef Hijji ◽  
Rajeesha Rajan ◽  
Hamdi Ben Yahia ◽  
Said Mansour ◽  
Abdelkader Zarrouk ◽  
...  
Keyword(s):  
Schiff Base ◽  
Molecular Orbital ◽  
Density Functional ◽  
Condensation Reaction ◽  
3D Structure ◽  
Water Soluble ◽  
Microwave Assisted Synthesis ◽  
One Pot ◽  
Microwave Assisted ◽  
Td Dft

The(3R,4R,6R)-3-(((E)-2-hydroxybenzylidene)amino)-6-(hydroxymethyl)tetrahydro-2H-pyran-2,4,5-triol water-soluble Glucose amine Schiff base (GASB-1) product was made available by condensation of 2-hydroxybenzaldehyde with (3R,6R)-3-amino-6-(hydroxymethyl)-tetra-hydro-2H-pyran-2,4,5-triol under mono-mode microwave heating. A one-pot 5-minute microwave-assisted reaction was required to complete the condensation reaction with 90% yield and without having byproducts. The 3D structure of GASB-1 was solved from single crystal X-ray diffraction data and computed by DFT/6-311G(d,p). The Hirshfeld surface analysis (HSA), molecular electronic potential (MEP), Mulliken atomic charge (MAC), and natural population analysis (NPA) were performed. The IR and UV-Vis spectra were matched to their density functional theory (DFT) relatives and the thermal behavior was resolved in an open-room condition via thermogravimetry/Derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). The highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO/LUMO), density of state (DOS), and time-dependence TD-DFT computations were correlated to the experimental electron transfer in water and acrylonitrile solvents.

Photophysical Properties of N-Methyl and N-Acetyl Substituted Alloxazine: A Theoretical Investigation

2021 ◽  
Author(s):  
Huimin Guo ◽  
Xiaolin Ma ◽  
Zhiwen Lei ◽  
Yang Qiu ◽  
Bernhard Dick ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Theoretical Investigation ◽  
Density Functional ◽  
Photophysical Properties ◽  
Time Dependent ◽  
Functional Theory ◽  
Td Dft ◽  
Dependent Density

The electronic structure and photophysical properties of a series of N-Methyl and N-Acetyl substituted alloxazine (AZs) were investigated with extensive density functional theory (DFT) and time-dependent density functional theory (TD-DFT)...

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