1D and 2D Solid State NMR of Homonuclear Systems using Magic Angle Spinning
Homonuclear two dimensional NMR techniques for liquids are one of the most important developments of the last two decades. However, many of these useful techniques have not been routinely applied to solids. The majority of homonuclear two dimensional NMR experiments depend on the presence of resolvable scalar couplings. In solids the non-commutativity of the dipolar coupling with the chemical shift for pairs of homonuclear spins has been shown to lead to severe broadening of the NMR lineshape even under MAS. In spite of these problems it can be shown that MAS spectra with resolved J couplings can be observed even when the differences in the anisotropic chemical shifts of coupled pairs of spins are the same order of magnitude as their dipolar coupling. To demonstrate that in many cases it is possible to perform two dimensional NMR experiments in the solid state on strongly coupled homonuclear spin systems, several compounds containing coupled pairs of 31P nuclei have been investigated.