P-31 AND C-13 CHEMICAL-SHIFT TENSORS IN ZIRCONIUM PHOSPHONATES

The orientations of the 31P phosphonate and 13C carboxyl chemical-shift tensors in the molecular frame of layered Zr(O3PCH2OOH)2 have been determined. The magnitudes of the three principal elements of these tensors were extracted from the 31P and 13C chemical-shift anisotropy (CSA) powder patterns, respectively, of Zr(O3PCH2OOH)2 The orientation of the principal axes of the 31P phosphonate chemical shielding tensor in Zr(O3PCH2OOH)2 was determined by simulating the 31P-13C dipolar perturbation of the 31p CSA powder pattern of 13C-labeled Zr(O3PCH2OOH)2. The least shielded tensor element, δ33, was found to lie in the PCC plane approximately 17° from the PC bond vector. The PCC plane also bisects the right angle formed by the remaining two tensor elements, δ11 and δ22. The orientation of the 13C carboxyl chemical shielding principal-axis system was determined by modeling the 13C13C perturbation of the 13C CSA powder pattern of Zr(O3PCH2OOH)2. This orientation was found to be typical of carboxylic acid shielding tensors previously reported in the literature. The most shielded tensor element, δ33, is nearly perpendicular to the COOH plane, while δ11 and δ22 lie in the COOH plane, with δ11 approximately 10° off the bisector of the OCO angle and δ22 approximately 20° off the C0 bond. © 1992.