Coupling constants angular dependence

I. Tvaroska and F. R. Taravel, One-bond carbon-proton coupling constants Angular dependence in a-linked oligosaccharides, Carbohydr. Res., 221 (1991) 83-94. 

I. Tvaroska, F.R. Taravel, One-bond carbon-proton coupling constants—angular-dependence in beta-linked oKgosaccharides, J. Biomol. NMR 2 (1992) 421-430. 

It is now generally realized that the angular dependence of vicinal coupling constants is considerably mare complex than was at first appreciated (24, 38, 39) and that care must be exercised in utilizing... 

Contreras, R. H., Peralta, J. E. Angular dependence of spin-spin coupling constants. Prog. Nucl. Magn. Reson. Spectrosc. 2000, 37, 321-425. 

Vicinal Coupling, V ( H, F). The signs of vicinal couplings were found to be absolutely positive, and their angular dependence parallels" that of proton-proton coupling-constants, - ranging between 0 and... 

Figure 3. INDO open shell hypersurface calculations for the hydrazine radical cation (23,24) contracted to 3 angular coordinates of freedom (cf. text) (A) INDO total energies vs. the B/w coordinate pair, and hypersurface maps for the dependence of the ESR hyperfine coupling constants, ajj (B and C) and ajj (D and E) on the dihedral angle w and the HNH bond angle a (B and D) or the out-of-plane bending angle B (C and E).

Summarizing, this example provides several take-home lessons complete sets of hypersurface calculations for main-frame models of compounds can be quite helpful in close correlation to experimental data. Obviously, both the radical cation ground state structure and the angular dependence of the coupling constants are correctly predicted. In return, by introducing experimental data into the established correlations, the structure of radical cations in solution may be cautiously approximated. Altogether, this example teaches another lesson on how drastic those structural changes may be, which accompany even one-electron redox reactions. 

Three-Bond Proton-Carbon Coupling Constants. Routine applications of the three-bond C-O-C-H proton-carbon coupling constants ( Jpu) have been coiqplicated by experimental difficulties involved in tneir measurement using classical H-coupled NMR spectroscopy and a limited knowledge of the angular dependence of for the C-O-C-H... 

The so-called Karplus relationship expresses approximately, the angular dependence of the vicinal coupling constant as ... 

Kurland and McGarvey approach [43] and an angular dependence of the contact coupling constant (as provided by the following Eq. (5.2)), by taking into account the contributions of the various electronic levels [44]. 

Fig. 13. Angular dependence of the isotropic hyperfine coupling constant for the jS-protons in RCH2CR2 radicals. The individual (dashed line) and total (solid line) couplings are shown.

We report an electron spin resonance (ESR) study on a C60 anion and a metal (M) encapsulated in fullerene (C ) (a metallofullerene M C ). The anisotropy components of the g-factor of Cg0 were determined accurately from the analysis of angular-dependent ESR spectra of single crystal Cg0 salt. The evaluation of the g-factor was performed according to the classification of symmetry of the C60 geometry. It was found out from the evaluation that the molecular structure of Cg0 should he distorted to lower symmetry, C2h or C,. The variety of ESR spectra of metallofullerenes of La C s was obtained in terms of a g-factor, a hyperfine coupling constant, and a line width. In the case of the isomer I of La C80 and the isomer II of La C84, an abnormally large line width was measured. The molecular structure with high symmetry would reflect on the specific spin dynamics. 

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