Chemical shift anisotropy amplification

Columnar self-assembly of N,N′,N′′-trihexylbenzene-1,3,5-tricarboxamides investigated by means of NMR spectroscopy and computational methods in solution and the solid state

“…In order to achieve these advantages and obtain a more reliable characterization of the shielding tensors associated with these three carbon environments, a two-dimensional approach was chosen. The 13 C CP CSA Amplification [39,40] spectrum of the BTA considered in this study is shown in Figure 7 each analyzed carbon environment is given by the 95% confidence interval as extracted from the rms deviation 2D contour plots shown in (e-g). [41,42,69] The parameters extracted at the minima of these 2D surfaces are given in Table 3 for the three sites of interest.…”

“…With respect to the anisotropy of the shift interaction, methods have been introduced that are not only capable of recoupling the inhomogeneity averaged out by the fast mechanical rotation, but also amplifying it, as if the experiment was performed at a slower and fictitious spinning rate. [37][38][39][40][41][42] This allows for more precise measurements of the full shielding tensor than those that one can achieve under static conditions or by spinning the sample at lower rates. [38] With respect to the chemical shift interaction, the following convention of NMR parameters is adopted in this study: [43] …”

Recoupling of chemical shift anisotropy by R-symmetry sequences in magic angle spinning NMR spectroscopy

“…Numerous methods have been developed to reintroduce the anisotropic chemical shift interactions in the indirect dimensions under MAS conditions. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] For most of these recoupling methods, determination of the CSA parameters requires analysis of the spinning sideband patterns 16, 21, 23, 26-29, 31, 32 or powder patterns, 15, 17-20, 22, 24, 25, 30 and usually periodic radio frequency (rf) field irradiation is applied in synchrony with the MAS sample rotation during the evolution period. In these recoupling techniques, the required rf field strengths are generally so high that, in practice, these sequences are only applicable under low or moderate MAS conditions.…”

Recent Advances in Solid‐State MAS NMR Methodology for Probing Structure and Dynamics in Polymeric and Supramolecular Systems

“…The experiment employs the principle of CSA amplification, [225] whereby the standard MAS spectrum in the direct (F 2 ) dimension is correlated with a sideband pattern in the indirect (F 1 ) dimension whose intensities should equal those that would be obtained for a MAS frequency that corresponds to the actual MAS frequency divided by the amplification factor. For the CAESURA experiment, the amplification pulse sequence is that described by Crockford et al [226] and Shao et al [227] Figure 23a and b presents two-dimensional 13 C CAESURA spectra of the a form of isotactic poly(propylene), iPP, at natural abundance in 13C recorded at 340 K with a mixing time of (Figure 23a) 0 and (Figure 23b) 1 s. [228] The CAESURA experiment used two sequences of five p pulses, yielding an amplification factor of 8, i.e. an effective MAS frequency of 375 Hz in the indirect dimension.…”