DEUTERIUM 2-DIMENSIONAL EXCHANGE NUCLEAR-MAGNETIC-RESONANCE BY ROTOR-SYNCHRONIZED MAGIC-ANGLE-SPINNING

The method of two-dimensional exchange spectroscopy under condition of magic angle sample spinning (MAS) and synchronization of the mixing time with the rotor period is extended to spin I = 1 nuclei. Theoretical equations are derived for the cross peak intensities as a function of the magnetic and kinetic parameters of the system and the method is demonstrated on a number of deuterated compounds. Dimethylmalonic acid-d6 is first used to illustrate the effect of rotor synchronization by the complete absence of cross peaks when no exchange takes place. The method is then applied to two dynamic systems, viz. dimethylsulfone-d6 and thiourea-C6D12 inclusion compound. The experimental results are compared with simulations as well as with analogous experiments on nonspinning samples. Since chemical shift effects are often negligible in deuterium NMR the time domain sampling can in principle be reduced to the number of the desired spinning sidebands, resulting in considerable time savings. The main advantage of the method is the gain in sensitivity at the expense of the characteristic ridge pattern of static two-dimensional exchange experiments. The gain in sensitivity may be sufficient for performing such experiments on deuterium in isotopically normal compounds. The feasibility of such experiments is demonstrated by the recording of a one-dimensional deuterium MAS spectrum of a nonenriched sample.