Shift Referencing

TiCU hquid or soHd SrTiOa as a CS reference. For the purposes of this review and the parameters aggregated in Table 1, the Ti 

AU chemical shifts and Knight shifts are referenced to the Ti resonance in neat TiCLj liquid at 0 ppm. The Euler angles are listed according to the Rose convention [98]. 

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Here, ak is the isotropic chemical shift referenced in ppm from the carrier frequency co0, SkSA is the anisotropy and tfk SA the asymmetry of the chemical-shielding tensor, here also expressed in ppm. Note that for heteronuclear cases different reference frequencies co0 are chosen for different nuclei (doubly rotating frame of reference). The two Euler angles ak and pk describe the orientation of the chemical-shielding tensor with respect to the laboratory-fixed frame of reference. The anisotropy dkSA defines the width and the asymmetry t]kSA the shape of the powder line shape (see Fig. 11.1a). 

Chemical shifts referenced to aqueous MgS04, t are peak positions J is an estimate N.D., not determined or not given. 

TMS cannot be used in aqueous solution because it is not water soluble. For a chemical-shift reference, a water-soluble equivalent (such as sodium d4-3-trimethylsilylpropanoate ((CH3)3SiCD2CD2C02-Na l, TSP )) can be added the single H peak is defined as zero ppm in water. The water peak itself can also be used as a chemical-shift reference, but care must be taken to correct for the temperature dependence of its chemical shift. Referencing of 13C and 15N chemical shifts can be done by using an accurate H reference. If the exact chemical shift is known at the center of the H spectral window (usually the water resonance), the precise radio frequency can be calculated for the zero point of the XH chemical-shift (ppm) scale. For example, on a 600 MHz spectrometer with a reference frequency of 600.13231564 MHz and a water chemical shift of 4.755 ppm ... 

The frequency contribution from a CS tensor also depends on the molecular orientation with respect to the external magnetic field. As illustrated in Figure 3(A), the principal axis system for a CS tensor is defined with the direction of the magnetic field in this text. A liquid sample of H20 is generally used for chemical shift referencing (set to be 0 ppm). Similar to the case of an 170 EFG tensor, a quantum chemical approach is useful for the spectral analysis. Since quantum chemical calculations yield the CS, o, the following conversion is required for making a direct comparison between theoretical and experimental values ... 

The chemical shifts of many nuclides of interest to the inorganic chemist, for example, P, ° Rh, and Pt, show large temperature, concentration and/or solvent shifts referencing to an absolute frequency, rather than a compound makes good sense. 

While pulsed experiments have failed to detect any signals in other systems, dispersion-mode spectra have been obtained on a number of simple organic compounds. (174) chemical shifts referenced to CS2 along with line-widths are in Table XIV. (174-176)... 

Key s, singlet l, triplet m, multiplet mainly a,-acid glycoprotein chemical shifts referenced to HI and Cl of a-glucose at S5.233 for H and at 892.9 for C. The bold font denotes the proton assignment. 

Chemical shifts referenced to Me4Si CFC13 Me4Si Me.N02 ... 

Tables. Structural data [62], molar ratios of T-atoms [221], mean Sanderson electronegativities Sm [222] of aluminosilicate frameworks, chemical shifts (referenced to TMS) [221], 8n, of bridging OH groups and H-Al distances [221 ], Thai, in the local structure of bridging OH groups derived by analysis of the H MAS NMR sideband patterns ...

Table 6. H MAS NMR shifts (referenced to TMS) and assignments of hydroxyl groups in...

The observed shift, referenced to 2,2-dimethyl-2-silapentane 5-sulfonate (DSS), boss for nucleus i is given by ... 

Saturated solution of PH3 in CDCI3. Standards are internal Si(CH3)4 and external PO(CH3)3. Infinitely diluted solutions of PH3 at 294 K. Shifts referenced to Si(CH3)4. Variations of 5( H) and J(P-H) with temperature (294 to 249 K) were given. Additional coupling constants J(P-H) ranging from 182 to 189 Hz were measured for PH3 in various isotropic and liquid-crystal solvents [13]. 

Table 1 summarizes the 5( Si) chemical shifts referenced against tetramethylsilane as well as important coupling constants for all compounds. 

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