13C and 31P chemical shielding tensors of a single crystal of dipotassium α- d-glucose-1-phosphate dihydrate. An application of a 13C-{ 1H, 31P} triple-resonance technique

Abstract

The 13C NMR spectra of a single crystal of dipotassium α- d-glucose-l-phosphate dehydrate for different orientations in the external magnetic field, were recorded by using 1H and 31P double nuclear decoupling. To overcome difficulties encountered because of the high 13C RF power required to achieve the Hartmann-Hahn condition, a new cross-polarization method (K. Takegoshi and C. A. McDowell, J. Magn. Reson. 67, 356 (1986)) was used. The directions of the most shielded principal value of the 13C chemical shielding tensors for the C2–C6 carbon nuclei in the glucose group were along the CO bond, and that for the CI carbon nucleus made an angle of 42† with the C1-O5 bond direction in the O1-C1-O5 plane. The 31P chemical shielding tensors are axially symmetric and the direction of the least shielded principal value is almost parallel to the P-O1(R) bond, which is the longest among the four PO bonds in the phosphate moiety.