Quantum effects and 1H NMR chemical shifts of a bifurcated short hydrogen bond

2020 ◽  
Vol 153 (11) ◽  
pp. 114301
Author(s):  
Shengmin Zhou ◽  
Lu Wang
Keyword(s):  
Hydrogen Bond ◽  
1H Nmr ◽  
Chemical Shifts ◽  
Quantum Effects ◽  
Nmr Chemical Shifts ◽  
Short Hydrogen Bond

Symmetry and 1H NMR chemical shifts of short hydrogen bonds: impact of electronic and nuclear quantum effects

2020 ◽  
Vol 22 (9) ◽  
pp. 4884-4895 ◽  
Author(s):  
Shengmin Zhou ◽  
Lu Wang
Keyword(s):  
Hydrogen Bonds ◽  
1H Nmr ◽  
Chemical Shifts ◽  
Quantum Effects ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Nuclear Quantum Effects ◽  
Short Hydrogen Bonds

Electronic and nuclear quantum effects determine the symmetry and highly downfield 1H NMR chemical shifts of short hydrogen bonds.

scholarly journals Solvent-Dependent Structures of Natural Products Based on the Combined Use of DFT Calculations and 1H-NMR Chemical Shifts

Molecules ◽  
2019 ◽  
Vol 24 (12) ◽  
pp. 2290 ◽  
Author(s):  
Saima H. Mari ◽  
Panayiotis C. Varras ◽  
Atia-tul-Wahab ◽  
Iqbal M. Choudhary ◽  
Michael G. Siskos ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Natural Products ◽  
Chemical Shift ◽  
Intramolecular Hydrogen Bond ◽  
1H Nmr ◽  
Chemical Shifts ◽  
Oh Groups ◽  
X Ray ◽  
Nmr Chemical Shifts ◽  
Intramolecular Hydrogen

Detailed solvent and temperature effects on the experimental 1H-NMR chemical shifts of the natural products chrysophanol (1), emodin (2), and physcion (3) are reported for the investigation of hydrogen bonding, solvation and conformation effects in solution. Very small chemical shift of │Δδ│ < 0.3 ppm and temperature coefficients │Δδ/ΔΤ│ ≤ 2.1 ppb/K were observed in DMSO-d6, acetone-d6 and CDCl3 for the C(1)–OH and C(8)–OH groups which demonstrate that they are involved in a strong intramolecular hydrogen bond. On the contrary, large chemical shift differences of 5.23 ppm at 298 K and Δδ/ΔΤ values in the range of −5.3 to −19.1 ppb/K between DMSO-d6 and CDCl3 were observed for the C(3)–OH group which demonstrate that the solvation state of the hydroxyl proton is a key factor in determining the value of the chemical shift. DFT calculated 1H-NMR chemical shifts, using various functionals and basis sets, the conductor-like polarizable continuum model, and discrete solute-solvent hydrogen bond interactions, were found to be in very good agreement with the experimental 1H-NMR chemical shifts even with computationally less demanding level of theory. The 1H-NMR chemical shifts of the OH groups which participate in intramolecular hydrogen bond are dependent on the conformational state of substituents and, thus, can be used as molecular sensors in conformational analysis. When the X-ray structures of chrysophanol (1), emodin (2), and physcion (3) were used as input geometries, the DFT-calculated 1H-NMR chemical shifts were shown to strongly deviate from the experimental chemical shifts and no functional dependence could be obtained. Comparison of the most important intramolecular data of the DFT calculated and the X-ray structures demonstrate significant differences for distances involving hydrogen atoms, most notably the intramolecular hydrogen bond O–H and C–H bond lengths which deviate by 0.152 tο 0.132 Å and 0.133 to 0.100 Å, respectively, in the two structural methods. Further differences were observed in the conformation of –OH, –CH3, and –OCH3 substituents.

Relativistic and Dynamic effects are needed to correctly model the 1H NMR Chemical Shifts of an Iridium Polyhydride Cluster

2020 ◽  
Author(s):  
Abril C. Castro ◽  
David Balcells ◽  
Michal Repisky ◽  
Trygve Helgaker ◽  
Michele Cascella
Keyword(s):  
1H Nmr ◽  
Chemical Shifts ◽  
Dynamic Effects ◽  
Nmr Chemical Shifts

scholarly journals Temperature dependence of 1H NMR chemical shifts and diffusivity of confined ethylammonium nitrate ionic liquid

2020 ◽  
Vol 74 ◽  
pp. 84-89 ◽  
Author(s):  
Oleg I. Gnezdilov ◽  
Oleg N. Antzutkin ◽  
Rustam Gimatdinov ◽  
Andrei Filippov
Keyword(s):  
Ionic Liquid ◽  
Temperature Dependence ◽  
1H Nmr ◽  
Chemical Shifts ◽  
Nmr Chemical Shifts ◽  
Ethylammonium Nitrate
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