Coupling Constants | ScienceGate

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of J-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Project model provides an affordable and practical approach for effectively correcting spin-contamination errors in molecular exchange coupling constant and spin crossover gap calculations.

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The Electron Effect of Aromatic Group: Control Conformation of 2-Aromatic Cyclododecanone Derivatives

Current Organic Chemistry ◽

10.2174/1385272824999200607175514 ◽

2020 ◽

Vol 24 (10) ◽

pp. 1139-1147

Author(s):

Yang Mingyan ◽

Wang Daoquan ◽

Wang Mingan

Keyword(s):

1H Nmr ◽

13C Nmr ◽

Nmr Spectra ◽

Coupling Constants ◽

The Other ◽

Repulsive Interaction ◽

X Ray Diffraction ◽

X Ray ◽

Electron Effect ◽

Group Control

2-Phenylcyclododecanone and 2-cyclohexylcyclododecanone derivatives were synthesized and characterized by 1H NMR, 13C NMR, HR-ESI-MS and X-ray diffraction. Their preferred conformations were analyzed by the coupling constants in the 1H NMR spectra and X-ray diffraction, which showed the skeleton ring of these derivatives containing [3333]-2-one conformation, and the phenyl groups were located at the side-exo position of [3333]-2-one conformation due to the strong π-π repulsive interaction between the π- electron of benzene ring and π-electron of carbonyl group. The cyclohexyl groups were located at the corner-syn or the side-exo position of [3333]-2-one conformation depending on the hindrance of the other substituted groups. The π-π electron effect played a crucial role in efficiently controlling the preferred conformation of 2-aromatic cyclododecanone and the other 2-aromatic macrocyclic derivatives with the similar preferred square and rectangular conformations.

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Chemical Shifts and Coupling Constants for Phosphorus-31

10.1007/978-3-642-41599-9 ◽

2014 ◽

Keyword(s):

Chemical Shifts ◽

Coupling Constants

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Conformational structure of ethylene glycol dibenzoate. Vibrational and NMR spectra

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19811913 ◽

1981 ◽

Vol 46 (8) ◽

pp. 1913-1929 ◽

Cited By ~ 3

Author(s):

Bohdan Schneider ◽

Pavel Sedláček ◽

Jan Štokr ◽

Danica Doskočilová ◽

Jan Lövy

Keyword(s):

Ethylene Glycol ◽

Vibrational Spectra ◽

Nmr Spectra ◽

Coupling Constants ◽

Conformational Structure ◽

Infrared And Raman Spectra ◽

H Nmr ◽

Liquid States ◽

Crystalline Forms ◽

C Nmr

It was found that three crystalline forms of ethylene glycol dibenzoate can be prepared. Infrared and Raman spectra of these three forms, as well as of the glassy and liquid states, were measured. From 3JHH coupling constants obtained by analysis of the 13C satellite band of the -CH2- group in 1H NMR spectra, and from the 3JCH coupling constants of the -CO.O.CH2- fragment obtained by analysis of the carbonyl band in 13C NMR spectra it was found that in the liquid state the -CH2-CH2- group exists predominantly in the gauche conformational structure, and the bonds C-O-C-C assume predominantly a trans orientation. The results of the analysis of NMR and vibrational spectra were used for the structural interpretation of conformationally sensitive bands in vibrational spectra of ethylene glycol dibenzoate.

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13C nuclear magnetic resonance study of cyclodipeptides containing 13C enriched hydrophobic amino acids

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19800482 ◽

1980 ◽

Vol 45 (2) ◽

pp. 482-490 ◽

Cited By ~ 10

Author(s):

Jaroslav Vičar ◽

François Piriou ◽

Pierre Fromageot ◽

Karel Bláha ◽

Serge Fermandjian

Keyword(s):

Amino Acids ◽

Nuclear Magnetic Resonance ◽

Nuclear Magnetic Resonance Study ◽

Coupling Constants ◽

Side Chain ◽

Amino Acid Residues ◽

Magnetic Resonance Study ◽

Side Chain Conformation ◽

13C Nuclear Magnetic Resonance ◽

Hydrophobic Amino Acids

The diastereoisomeric pairs of cyclodipeptides cis- and trans-cyclo(Ala-Ala), cyclo(Ala-Phe), cyclo(Val-Val) and cyclo(Leu-Leu) containing 85% 13C enriched amino-acid residues were synthesized and their 13C-13C coupling constants were measured. The combination of 13C-13C and 1H-1H coupling constants enabled to estimate unequivocally the side chain conformation of the valine and leucine residues.

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Carbon-13 and nitrogen-14 NMR spectra of 1-(substituted phenyl)pyridinium salts

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19802766 ◽

1980 ◽

Vol 45 (10) ◽

pp. 2766-2771 ◽

Cited By ~ 8

Author(s):

Antonín Lyčka

Keyword(s):

Heavy Water ◽

Nmr Spectra ◽

Chemical Shifts ◽

Coupling Constants ◽

Pyridinium Salts ◽

Nmr Signals ◽

C Nmr

The 13C and 14N NMR spectra of 1M solutions of 1-(substituted phenyl)pyridinium salts (4-CH3, 4-OCH3, H, 4-Cl, 4-Br, 4-I, 3-NO2, 4-NO2, 2,4-(NO2)2 (the 13C NMR only)) have been measured in heavy water at 30 °C. The 13C and 14N chemical shifts, the 1J(CH) coupling constants, some 3J(CH) coupling constants, and values of half-widths Δ 1/2 of the 14N NMR signals are given. The 13C chemical shifts of C(4) correlate with the σ0 constants (δC(4) = (1.79 ± 0.097) σ0 + (147.67 ± 0.041)), whereas no correlation of the nitrogen chemical shifts with the σ constants has been found. The half-widths Δ 1/2 correlate with the σ0 constants (Δ 1/2 = (76.2 ± 4.9) σ0 + (106.4 ± 2.2)) except for 1-phenylpyridinium chloride.

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