J-upscaling in two-dimensional solid-state NMR spectroscopy

Abstract

The direct measurement of homonuclear scalar couplings (J) in solids, which serve as important parameters for the elucidation of molecular structure/ characterization of materials, is difficult due to the inherent broadening of spectral lines in the solid-state NMR. The earlier reported J-measurements in solid-state NMR are based on 1D/ pseudo 2D spin echo modulation techniques, which rely on computing the J-values by fitting the spin-echo modulations to appropriate mathematical functions, and may involve expertise in the area. On the other hand, the present study demonstrates two simple 2D-NMR methods: J-upscaled mechanism uniform cross-peak double quantum filtered COSY (JS-UC2QFCOSY) and its selective refocusing variant JS2-UC2QFCOSY that allow an easy quantification of scalar couplings, which have been exemplified for unambiguous measurement of JCC values in 13C3-alanine and 13C6-histidine.2HCl samples. These versatile experimental approaches are expected to be highly useful in structural characterizations of organic solids and other materials.