Double quantum 1H MAS NMR studies of hydrogen-bonded protons and water dynamics in materials.
Two-dimensional double quantum (DQ) 1H MAS NMR was used to investigate different proton environments in a series of alkali (Na, K, Rb, Cs) [Nb6O19]8- Lindqvist salts, with the water and hydrogen-bound intercluster protons being clearly resolved. Through the analysis of the DQ 1H NMR spinning sideband pattern, it is possible to extract both the mean and distribution of the motionally averaged intramolecular homonuclear 1H-1H dipolar coupling for the different water environments and the intercluster protons. Motional order parameters for the water environments were then calculated from the averaged dipolar couplings. The influence of additional intermolecular dipolar couplings due to multispin interactions were simulated and discussed.
Alam
Todd M
TM
Department of Nanostructured and Electronic Materials, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA. tmalam@sandia.gov
Nyman
May
M
McIntyre
Sarah K
SK