Product operator theory for ABX spin systems and its application to H-C-C INEPT NMR experiments

Abstract

Product operator theory was extended to be applicable to ABX three-spin systems; previously, the product operator method had not been used for exact estimation of the time evolution of such systems because of the presence of strong couplings. The theory was applied to describe two types of experiment regarding ¹³C-¹³C-¹H spin systems, namely, INEPT-INADEQUATE and C-relayed H-C INEPT experiments, where ¹H magnetizations are transferred to enhance insensitive ¹³C-¹³C signals in ¹³C natural abundance samples. The theory predicted that various kinds of coherences, unexpected for weakly coupled systems, may be generated via ¹³C-¹³C strong couplings. Experiments performed on methyl benzoate demonstrated novel effects intrinsic to strongly coupled ¹³C-¹³C-¹H (ABX) systems, verifying the theoretical treatments.