Chapter 22: Long-lived Spin Order in CH₂D Groups

The ubiquitous nature of methyl groups makes the potential exploitation of methyl long-lived states particularly attractive. However, access to methyl group long-lived states is only provided by inefficient cross-relaxation processes that greatly reduce the available intensity of the resulting proton signal. Monodeuterated methyl groups provide a plausible alternative to pump long-lived states with high efficiency in this common moiety. In this chapter, the proton long-lived state in the monodeuterated group of a unique piperidine complex is presented, with the ratio of the singlet lifetime to the spin–lattice decay time found to be remarkably constant over a wide range of experimental conditions. These results demonstrate the advantages of accessing methyl long-lived states coherently without exploiting weak cross-relaxation phenomena.