Two-Dimensional NMR Spectroscopy

Abstract

Spectroscopy usually employs one frequency axis along which the signal intensity is plotted. In high resolution NMR spectroscopy in liquids a wealth of overlapping lines of different nuclear species is commonly observed. The same statement applies to solid state NMR especially if high resolution techniques are applied as described in this monograph. The reader should be aware, that so far only simple highly resolved solid state spectra have been discussed in order to present simple examples. In practice, however, lines of different nuclear species with possibly different near neighbour couplings do often overlap especially in powder samples. A technique is therefore desirable, which employs a second frequency axis representing a different interaction of the spins than the first one. The spectra would be disentangled and correlations could be visualized. Such a technique was proposed for liquids by Jeener [1] at a summer school in Jugoslavia and has been further developed by Ernst and coworkers [2–4] and by Freeman and co-workers [5, 6]. Waugh and co-workers [7–10], Stoll, Vega and Vaughan [11] and Alia and Lippmaa [12] designed 2D-experiments specifically tailored for solid state applications. Since then numerous variations of these basic experiments have been proposed. Some of these we will deal with in Sect. 5.4. Space does not permit a complete review of 2D-spectroscopy. We therefore restrict ourselves to the basic principles (Sect. 5.1) and some applications in solid state NMR.