Abstract
The development of homonuclear dipolar decoupling sequences to obtain high-resolution 1H NMR spectra from solids has recently celebrated its 50th birthday. Over the years, a series of different decoupling schemes have been developed, starting with the pioneering Lee-Goldburg and WAHUHA sequences up to the most recent generation of experimentally optimized phase-modulated schemes such as eDUMBO-122 and LG4. These schemes can all yield over an order of magnitude reduction in 1H NMR linewidths in solids. Here we provide an overview and a broad experimental comparison of the performance of the main sequences, which has so far been absent in the literature, especially between the newest and the oldest decoupling schemes. We compare experimental results obtained using eight different decoupling schemes (LG, WHH-4, MREV-8, BR-24, FSLG/PMLG, DUMBO-1, eDUMBO-122 and LG4) on three different microcrystalline powdered samples (alanine, glycine and β-AspAla) and at three different MAS rates (3.0, 12.5 and 22.0 kHz). Finally, since these sequences can be technically demanding, we describe the experimental protocol we have used to optimize these schemes with the aim to provide simple guidelines for the optimization of CRAMPS experiments for all NMR users.
Highlights
Just over 50 years ago, the pioneering works of Lee and Goldburg [1,2] and Waugh and co-workers [3] revolutionized the world of solid-state nuclear magnetic resonance (NMR) with the introduction of the Lee-Golburg (LG) and WAHUHA (WHH-4) pulse sequences respectively
We provide a comparison of CRAMPS experiments using eight homonuclear dipolar decoupling sequences: LG, WHH-4, MREV-8, BR-24, PMLG, decoupling using mind-boggling optimization (DUMBO)-1, eDUMBO-122 and LG4
When we look at the four phase-modulated schemes PMLG, DUMBO-1, eDUMBO-122, and LG4 we first see that again they all give very significantly better performance than the original LG scheme
Summary
Just over 50 years ago, the pioneering works of Lee and Goldburg [1,2] and Waugh and co-workers [3] revolutionized the world of solid-state nuclear magnetic resonance (NMR) with the introduction of the Lee-Golburg (LG) and WAHUHA (WHH-4) pulse sequences respectively. Following the principles of coherent averaging [4], these pulse sequences can remove the broadening effects of homonuclear dipolar couplings in solid samples, while leaving the chemical shift interactions (at least partially) intact. Despite their technical differences, both LG and WHH-4 work in a very similar way: they generate a rotation of the spin operators in the spin space around an effective field tilted of 54.74° with respect of the main static magnetic field. The result is that the homonuclear dipolar coupling is averaged to zero (to first order), in a manner similar to that achieved by magic angle sample spinning (MAS) [5,6], while
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
