Variable-temperature dynamic proton NMR nitrogen-hydrogen line-shape analysis for meso-monosubstituted octaethylporphyrins: an indication of remarkably slow N-H tautomerism

1992 ◽  
Vol 57 (21) ◽  
pp. 5796-5798 ◽  
Author(s):  
Masumi Asakawa ◽  
Hiroo Toi ◽  
Yasuhiro Aoyama ◽  
Hisanobu Ogoshi
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Variable Temperature ◽  
Proton Nmr ◽  
Hydrogen Line ◽  
Line Shape Analysis ◽  
Temperature Dynamic

Lanthanide complexes of an oxazoline-phenoxide hybrid chelate

2005 ◽  
Vol 83 (5) ◽  
pp. 449-459 ◽  
Author(s):  
David J Berg ◽  
Chuanjian Zhou ◽  
Tosha Barclay ◽  
Xuening Fei ◽  
Shengyu Feng ◽  
...  
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Variable Temperature ◽  
Paramagnetic Nmr ◽  
Dynamic Features ◽  
X Ray ◽  
X Ray Crystallography ◽  
Line Shape Analysis ◽  
Mechanistic Investigation ◽  
Bailar Twist

The synthesis of 2-(2′-hydroxy-3′-allylphenyl)-4,4-dimethyl-2-oxazoline, H-Allox (3), and lanthanide tris chelate complexes, mer-Ln(Allox)3 (Ln = La (4), Ce (5), Sm (6), Er (7), and Y (8)), derived from it are reported. A six-coordinate mer geometry without alkene coordination was confirmed in the solid state by X-ray crystallography for 5 and 7. Variable-temperature NMR experiments suggested that this is the most stable isomer in solution as well, although the inequivalent ligand environments undergo rapid averaging at room temperature for all five complexes. A mechanistic investigation indicated that this fluxional process is an intramolecular six-coordinate rearrangement, but it was not possible to distinguish between a Bailar (trigonal) or Rây–Dutt (rhombic) twist. Kinetic parameters for the fluxional process were determined by line shape analysis for 8 yielding ΔH‡ = 24 ± 2 kJ mol–1 and ΔS‡ = –99 ± 10 J mol–1 K–1. The structural and dynamic features of 4–8 were compared with the related In, Ga, and Al tris(2-oxazolylphenoxides).Key words: oxazoline, phenoxide, lanthanide, Group 3, Rây–Dutt twist, Bailar twist, Eyring plot, X-ray crystallography, mer isomer, variable-temperature NMR, line shape analysis, dynamic NMR, paramagnetic NMR, bidentate ligands.

A variable-temperature cavity ring-down spectrometer with application to line shape analysis of CO2 spectra in the 1600 nm region

2017 ◽  
Vol 123 (4) ◽  
Author(s):  
Mélanie Ghysels ◽  
Qingnan Liu ◽  
Adam J. Fleisher ◽  
Joseph T. Hodges
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Variable Temperature ◽  
Line Shape Analysis ◽  
Cavity Ring Down

Assessment of the flexibilities of carbohydrate polymers by proton-NMR relaxation and line shape analysis

1982 ◽  
Vol 15 (2) ◽  
pp. 597-602 ◽  
Author(s):  
S. Ablett ◽  
A. H. Clark ◽  
D. A. Rees
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Proton Nmr ◽  
Nmr Relaxation ◽  
Carbohydrate Polymers ◽  
Line Shape Analysis

Determination of the Accurate Values of the Rate Constant and Thermodynamic Parameters for the Rotation About the C(sp2)-C(aryl) Bond; Adamantan-1-yl 3-Bromo-2,4,6-trimethylphenyl Ketone

1998 ◽  
Vol 63 (7) ◽  
pp. 955-966
Author(s):  
Eva Přibylová ◽  
Miroslav Holík
Keyword(s):  
Thermodynamic Parameters ◽  
Shape Analysis ◽  
Rate Constants ◽  
Line Shape ◽  
Microsoft Excel ◽  
Hindered Rotation ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Coalescence Temperature

Four programs for the 1H NMR line shape analysis: two commercial - Winkubo (Bruker) and DNMR5 (QCPE 165) and two written in our laboratory - Newton (in Microsoft Excel) and Simtex (in Matlab) have been tested in order to get highly accurate rate constants of the hindered rotation about a single bond. For this purpose four testing criteria were used, two of them were also developed by us. As supplementary determinations the rate constants obtained for the coalescence temperature and for the thermal racemization of chromatographically separated enantiomers were used which fitted well the temperature dependence of the rate constants determined by the line shape analysis. As a test compound adamantan-1-yl 3-bromo-2,4,6-trimethylphenyl ketone was prepared and studied. It was shown that supermodified simplex method used in our algorithm (Simtex), though time consuming, gives the most accurate values of the rate constants and consequently the calculated thermodynamic parameters Ea, ∆H≠, and ∆S≠ lay in relatively narrow confidence intervals.

Cope rearrangement of 9-methylenebarbaralane. Complete line shape analysis

1973 ◽  
Vol 38 (6) ◽  
pp. 1210-1215 ◽  
Author(s):  
Linda G. Greifenstein ◽  
Joseph B. Lambert ◽  
Michael J. Broadhurst ◽  
Leo A. Paquette
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Cope Rearrangement ◽  
Line Shape Analysis
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