Limitations of lanthanide shift reagents for determination of conformation of nonrigid molecules

1976 ◽  
Vol 98 (23) ◽  
pp. 7162-7169 ◽  
Author(s):  
Glenn R. Sullivan
Keyword(s):  
Nonrigid Molecules ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents

Use of lanthanide shift reagents for the determination of the alkyl conformation in 2-alkyl-2-adamantanols

1977 ◽  
Vol 10 (1) ◽  
pp. 52-55 ◽  
Author(s):  
M. Hájek ◽  
P. Trška ◽  
L. Vodička ◽  
J. Hlavatý
Keyword(s):  
Lanthanide Shift Reagents ◽  
Shift Reagents

Halogen substituted adamantanones. Structural studies with lanthanide shift reagents

1988 ◽  
Vol 53 (1) ◽  
pp. 97-109 ◽  
Author(s):  
Milan Hájek ◽  
Alena Horská ◽  
Petr Trška ◽  
Luděk Vodička ◽  
Douglas J. Raber ◽  
...  
Keyword(s):  
Bond Length ◽  
Optimization Procedure ◽  
Step Size ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Empirical Force Field ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents ◽  
Empirical Force Field Calculations

Europium shift reagents (both FOD and DPM) have been used to study a series of halogen substituted adamantanones by 1H NMR spectroscopy. Reliable correlations of molecular structure with the lanthanide induced shifts can be obtained only if certain precautions are taken. The source of atomic coordinates used to predict induced shifts with the pseudocontact equation is critical; coordinates by X-ray crystallography can be unreliable for this purpose, while those from empirical force field calculations yield satisfactory results. Determination of the europium-oxygen bond length by optimization of the agreement factor is shown to be inadequate. Even with a restricted Eu-O bond length, calculation of the best lanthanide position is shown to be dependent on the step size by which the lanthanide is moved in the optimization procedure. All of the compounds studied were found to give complexes with approximately linear C-O-Eu arrays, and the distortions from linearity are consistent with steric effects.

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