THE RELATION OF 15N NMR, 1H NMR CHEMICAL SHIFTS WITH THE ATOMIC NET CHARGE AND MOLECULAR STRUCTURES

1987 ◽  
Vol 3 (06) ◽  
pp. 632-637
Author(s):  
Chen Yuehua ◽  
◽  
Guo Guolin ◽  
Shen Qifeng ◽  
Zhao Yufen ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Molecular Structures ◽  
Net Charge ◽  
Nmr Chemical Shifts ◽  
H Nmr

Effects of porphyrin deformation on the 13C and 1H NMR chemical shifts in high-spin five- and six-coordinate manganese(III) porphyrin complexes

2016 ◽  
Vol 20 (01n04) ◽  
pp. 318-330 ◽  
Author(s):  
Akira Ikezaki ◽  
Mikio Nakamura
Keyword(s):  
Spin Polarization ◽  
High Spin ◽  
Chemical Shifts ◽  
Deformation Mode ◽  
Crystallographic Analysis ◽  
Molecular Structures ◽  
Metal Porphyrin ◽  
Nmr Chemical Shifts ◽  
Orbital Interactions ◽  
H Nmr

As an extension of our study to reveal the effect of porphyrin deformation on the [Formula: see text]C and 1H NMR chemical shifts, both five- and six-coordinate high-spin (S [Formula: see text] 2) Mn(III) complexes such as Mn(Por)Cl and [Mn(Por)(CD3OD)2]Cl have been prepared, where Por is a porphyrin dianion such as TPP, OMTPP, and T[Formula: see text]PrP. Molecular structures of five-coordinate Mn(OMTPP)Cl and Mn(TiPrP)Cl have been determined by the X-ray crystallographic analysis. As expected, Mn(OMTPP)Cl and Mn(TiPrP)Cl have exhibited a highly saddled and highly ruffled porphyrin core, respectively. The [Formula: see text]C NMR spectra have revealed that these complexes generally exhibit the [Formula: see text]-pyrrole signals at the downfield positions and [Formula: see text]-pyrrole an. meso signals at the upfield positions. The results suggest that the spin polarization of Mn(III)–NP σ bonds, which occurs in all the high-spin Mn(III) complexes, is the major factor to determine the chemical shifts of the porphyrin carbon signals (Cheng, R.-J.; Chang, S.-H.; Hung, K.-C. Inorg. Chem. 2007; 46: 1948–1950). Although th. meso and [Formula: see text]-pyrrole signals are observed at the upfield and downfield positions, respectively, these signals are widely dispersed depending on the deformation mode of the porphyrin ring. The results have been explained in terms of the strong spin polarization of the Mn–NP bond together with the specific metal-porphyrin orbital interactions such as: (i) the a2u-dz2 interaction in five-coordinate complexes, (ii) the a2u-dxy interaction in ruffled complexes, and (iii) the a2u-dx2-y2 interaction in saddled complexes.

Spirocyclic tin salicyl alcoholates – a combined experimental and theoretical study on their structures, 119Sn NMR chemical shifts and reactivity in thermally induced twin polymerization

2019 ◽  
Vol 48 (1) ◽  
pp. 220-230
Author(s):  
Philipp Kitschke ◽  
Ana-Maria Preda ◽  
Alexander A. Auer ◽  
Sebastian Scholz ◽  
Tobias Rüffer ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Chemical Shifts ◽  
Molecular Structures ◽  
Thermally Induced ◽  
Nmr Chemical Shifts ◽  
119Sn Nmr

Studies on a series of spirocyclic tin salicyl alcoholates regarding their molecular structures and their reactivity in twin polymerization are presented.

scholarly journals General QSPR Protocol for Atomic/Inter-atomic Properties Predictions: Fragments based Graph Convolutional Neural Network (F-GCN)

2021 ◽  
Author(s):  
Peng Gao ◽  
Jie Zhang ◽  
Hongbo Qiu ◽  
Shuaifei Zhao
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
Density Functional ◽  
Chemical Shifts ◽  
Computational Cost ◽  
Accurate Solution ◽  
Structure Property ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Atomic Properties

In this study, a general quantitative structure-property relationship (QSPR) protocol, fragments based graph convolutional neural network (F-GCN), was developed for atomic and inter-atomic properties predictions. We applied this novel artificial intelligence (AI) tool in NMR chemical shifts and bond dissociation energies (BDEs) predictions. The predicted results were comparable to experimental measurement, while the computational cost was substantially reduced, with respect to pure density functional theory (DFT) calculations. The two important features of F-GCN can be summarised as: first, it could utilise different levels of molecular fragments centered at the target chemical bonds for atomic and inter-atomic information extraction; second, the designed architecture is also open to include additional descriptors for more accurate solution of chemical environment, making itself more efficient for local properties descriptions. And during our test, the averaged prediction error of <sup>1</sup>H NMR chemical shifts can be as small as 0.32 ppm; and the error of C-H BDEs estimations, is 2.7 kcal/mol. Moreover, we further demonstrated the applicability of this developed F-GCN model via several challenging structural assignments. The success of the F-GCN in atomic and inter-atomic predictions also indicates an essential improvement of computational chemistry with the assistance of AI tools.

Halogenation of Tris(amido)tantalacarboranes with Dihalomethanes CH2X2 (X = Cl, Br)

2002 ◽  
Vol 67 (6) ◽  
pp. 791-807 ◽  
Author(s):  
Mark A. Fox ◽  
Andrés E. Goeta ◽  
Andrew K. Hughes ◽  
John M. Malget ◽  
Ken Wade
Keyword(s):  
Single Crystal ◽  
Prolonged Exposure ◽  
Chemical Shifts ◽  
Amide Group ◽  
The Other ◽  
X Ray ◽  
Nmr Chemical Shifts ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Hydrolysis Of

Slow reactions of isomeric metallacarboranes of general formulae [(NMe2)3TaC2B9H11] (3 isomers) and [(NMe2)3TaC2B9H10Me] (3 isomers) with CD2Cl2 afford quantitative yields of monochloro complexes [Cl(NMe2)2TaC2B9H11] and [Cl(NMe2)2TaC2B9H10Me]. Exposure to CD2Cl2 for months leads to solutions containing about 70% of the dichlorides in three cases. More prolonged exposure of these and the other monochlorides leads to a mixture of boron-substituted complexes. Hydrolysis of [3,3,3-(NMe2)3-3,1,2-TaC2B9H11] by moist toluene results in the formation of the oxo-bridged complex 3,3'-[3,3-(NMe2)2-3,1,2-TaC2B9H11]2(μ-O), characterised by single-crystal X-ray crystallography. The limited solubility of the latter complex in CD2Cl2 eliminates the presence of this compound in the reaction of [3,3,3-(NMe2)3-3,1,2-TaC2B9H11] with CD2Cl2. The reaction of [2,2,2-(NMe2)3-2,1,12-TaC2B9H11] with CH2Br2 in C6D6 quantitatively yields the monobromide [2-Br-2,2-(NMe2)2-2,1,12-TaC2B9H11]. Prolonged reaction with CH2Br2 leads directly to isomeric boron-substituted complexes with no evidence for dibromides. The influence on 11B, 13C and 1H NMR chemical shifts of replacing an amide group in [(NMe2)3TaC2B9H11] with chloride to give [Cl(NMe2)2TaC2B9H11] is also discussed.

Polar effects on 13C NMR chemical shifts and rotational barriers of amides. A dual substituent parameters analysis of N,N-dimethyl-3-(5-substituted-2-furyl)-acrylamides

1987 ◽  
Vol 52 (2) ◽  
pp. 409-424 ◽  
Author(s):  
Zdeněk Friedl ◽  
Stanislav Böhm ◽  
Igor Goljer ◽  
Anna Piklerová ◽  
Daniela Poórová ◽  
...  
Keyword(s):  
Substituent Effect ◽  
Chemical Shifts ◽  
Polar Effect ◽  
Dominant Factor ◽  
Side Chain ◽  
Nmr Chemical Shifts ◽  
Resonance Effects ◽  
H Nmr ◽  
Reverse Substituent Effect ◽  
C Nmr

13C NMR chemical shifts were measured for sixteen N,N-dimethyl-3-(5-substituted-2-furyl)-acrylamides in CDCl3 at 21 °C; the barriers of rotation about the C-N bond ΔGc° were determined by using the 1H NMR coalescence method, and the positions of the IR bands of the ν(C=O) stretching vibrations were measured. The dual substituent parameters (DSP) analysis of the 13C NMR chemical shifts for atoms of the vinylcarboxamide side chain -C(3)H=C(2)H-C(1)=O(-N) gives evidence that the chemical shifts for the C-1 and C-3 atoms are controlled primarily by polar effects (δ(C-3) = -3.12σI - 1.03σR0; λ = ρI/ρR = 3.0), which exert a reverse substituent effect on these atoms. Similarly, the DSP analysis of the ΔGc° and ν(C=O) data shows that the dominant factor of the total substituent effect is the polar effect (λ = 1.95 and 1.70, respectively). A confrontation of the results of the DSP analysis with the CNDO/2 calculated electron densities at the corresponding atoms demonstrates that the reactivity of the entire vinylcarboxamide side chain can be well explained in terms of a combination of the polar effect (π-electron polarization) with resonance effects.

Quantitative relations between chemical structure and hepatotoxicity of thiobenzamides

1988 ◽  
Vol 53 (11) ◽  
pp. 2957-2961 ◽  
Author(s):  
Karel Waisser ◽  
Miloš Macháček ◽  
Jean Lebvoua ◽  
Jiří Hrbata ◽  
Jaroslav Dršata
Keyword(s):  
Chemical Structure ◽  
Chemical Shifts ◽  
Phenyl Group ◽  
Total Effect ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Hammett Constants ◽  
Thioamide Group

1H NMR chemical shifts of thioamide protons have been determined for a group of thiobenzamides, and the values obtained have been correlated with the Hammett constants. From the relations found the σm and σp values of thioamide group and some other σ constants describing the total effect of two substituents in the phenyl group have been calculated. The relation between the hepatotoxicity for rats (expressed as log ALT) and the Hammett constants is described by equation of parabola.

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.

15N, 13C, and 1H NMR spectra of acylated ureas and thioureas

1987 ◽  
Vol 52 (10) ◽  
pp. 2474-2481 ◽  
Author(s):  
Josef Jirman ◽  
Antonín Lyčka
Keyword(s):  
1H Nmr ◽  
Electron Acceptor ◽  
Sulfur Atom ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
1H Nmr Spectra ◽  
Coupling Constants ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Better Than

A series of 1-acylated and 1,3-diacylated (acyl = acetyl or benzoyl) ureas and thioureas have been prepared and their proton-coupled and proton-decoupled 15N, 13C, and 1H NMR spectra have been measured. All the signals have been assigned. The 15N NMR chemical shifts in 1-acylated ureas and thioureas are shifted downfield as compared with δ(15N) of urea and thiourea, resp. This shift is greater for N-1 than for N-3 nitrogen atoms in both the series. When comparing acylureas and acylthioureas it is obvious from the Δδ(15N) differences that the CS group is better than CO group in transferring the electron-acceptor effect of acyl group. The proton-coupled 15N NMR spectra of the acylureas dissolved in hexadeuteriodimethyl sulphoxide exhibit a doublet of NH group and a triplet of NH2 group at 25 °C. At the same conditions the acylthioureas exhibit a doublet of NH group, the NH2 group signal being split into a doublet of doublets with different coupling constants 1J(15N, H). The greater one of these coupling constants is due to the s-trans proton with respect to the sulfur atom of the thiourea.

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