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Keywords = GIAO-SCF

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16 pages, 6084 KiB  
Article
ExoEndo Isomerism, MEP/DFT, XRD/HSA-Interactions of 2,5-Dimethoxybenzaldehyde: Thermal, 1BNA-Docking, Optical, and TD-DFT Studies
by Nabil Al-Zaqri, Mohammed Suleiman, Anas Al-Ali, Khaled Alkanad, Karthik Kumara, Neartur K. Lokanath, Abdelkader Zarrouk, Ali Alsalme, Fahad A. Alharthi, Afnan Al-Taleb, Amjad Alsyahi and Ismail Warad
Molecules 2020, 25(24), 5970; https://doi.org/10.3390/molecules25245970 - 16 Dec 2020
Cited by 7 | Viewed by 3166
Abstract
The exoendo 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 [...] Read more.
The exoendo 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. Full article
(This article belongs to the Special Issue Inorganic Materials Chemistry)
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8 pages, 238 KiB  
Article
A New Graphical Model for Proton NMR (De)shielding over a Carbon-Carbon Double Bond to Replace the Shielding Cone Model
by Ned H. Martin and Justin D. Brown
Int. J. Mol. Sci. 2000, 1(4), 84-91; https://doi.org/10.3390/ijms1040084 - 14 Nov 2000
Cited by 12 | Viewed by 10937
Abstract
The long-held “shielding cone” model of the through-space NMR shielding effect of a carbon-carbon double bond predicts only the effect of the magnetic anisotropy of the double bond; it ignores other important contributors to the overall shielding. GIAO-SCF and GIAO-MP2 calculations have been [...] Read more.
The long-held “shielding cone” model of the through-space NMR shielding effect of a carbon-carbon double bond predicts only the effect of the magnetic anisotropy of the double bond; it ignores other important contributors to the overall shielding. GIAO-SCF and GIAO-MP2 calculations have been performed on a simple model system, methane moved sequentially above ethene or 2-methylpropene. These calculations permit the net NMR shielding surface to be mapped. Based on those results, a new and very different graphical model for predicting the effect of a proton’s position relative to a carbon-carbon double bond on its chemical shift is presented. Full article
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