Sum‐over‐states density functional perturbation theory: Prediction of reliable 13C, 15N, and 17O nuclear magnetic resonance chemical shifts

1996 ◽  
Vol 105 (20) ◽  
pp. 8995-9006 ◽  
Author(s):  
Lars Olsson ◽  
Dieter Cremer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Perturbation Theory ◽  
Magnetic Resonance ◽  
Density Functional ◽  
Chemical Shifts ◽  
Density Functional Perturbation Theory ◽  
Nuclear Magnetic

Use of Replaced Chalcones to Generate a 13C Chemical Shift Staging Factor for Chalcone and Its Derivate

2020 ◽  
Vol 12 (4) ◽  
pp. 464-472
Author(s):  
Thaís F. Giacomello ◽  
Gunar V. da S. Mota ◽  
Antônio M. de J. C. Neto ◽  
Fabio L. P. Costa
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Density Functional ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Scaling Factor ◽  
Orbital Method ◽  
Beneficial Effects ◽  
Nuclear Magnetic

Chalcones have attracted the attention of researchers for decades, they are biologically classified as secondary metabolites of low molecular weight. These are considered as the precursors of flavonoids and they are widely distributed in plants such as vegetables, fruits, teas and spices. It has been demonstrating that chalcones possess many important bioactivities including properties of antioxidants and other evidence of its potential beneficial effects on health. Chalcone compounds and its derivatives have been showing a growing interest in the therapeutic properties. Nuclear magnetic resonance (NMR) spectroscopy is one of the most important tools for determining the structures of organic molecules. In the work present a 13C Nuclear magnetic resonance chemical shift protocol of chalcones and derivative based on the application of scaling factor with chalcone molecules. This protocol consists of using density functional theory with gauge-including atomic orbital method to calculating 13C chemical shifts and the application of a parameterized scaling factor in order to ensure accurate structural determination of chalcones and derivative.

Systematic Gauge-Including Atomic Orbital-Hybrid Density Functional Theory Linear Regressions for 13C NMR Chemical Shifts Calculation

2020 ◽  
Vol 12 (3) ◽  
pp. 364-370
Author(s):  
Sara Sâmitha Souza ◽  
Mariana Aparecida de Souza Martins ◽  
Antonio Maia de Jesus Chaves Neto ◽  
Gunar Vingre Da Silva Mota ◽  
Fabio Luiz Paranhos Costa
Keyword(s):  
Density Functional Theory ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Density Functional ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Basis Set ◽  
Functional Theory ◽  
Linear Regressions ◽  
Nuclear Magnetic

Density-functional theory calculations of the magnetic shielding for nuclear magnetic resonance provide an important contribution to understand the experimental values obtained in laboratory for chemical shifts present in the samples. From of a comparative of the performance of ten hybrid functional within of the framework of the density-functional theory using 10 different hybrid functionals with 3-21G (B1), 6-31G(d) (B2) and 6-31+ G(d, p) (B3) basis set, with intuit of evaluating of performance of the 13 C nuclear magnetic resonance from a representative of the terpene class and a heterocyclic compound, (–)-loliolide ((7aR)-6-hydroxy-4,4,7a-trimethyl-6,7-dihydro-5H1-benzofuran-2-one). This molecule, satisfactorily, represents the main structure of this class, with conformational freedom, optical activity and a benzofuran nucleus. The ωB97X-D, MPW1K and HSEH1PBE functionals presented the best calculation performance. It is interesting to note that after the use of linear regressions all root mean square error values for ωB97X-D were lower than 3 ppm. These are 2.91 ppm (B1), 2.46 (B2) ppm and 2.62 ppm (B3). The information contained in this work can be used for the assignment of experimental nuclear magnetic resonance spectra and will motivate further studies involving the theoretical calculation of the chemical shift of 13C.

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