Pure shift ¹H NMR: what is next?

Abstract

Currently, pure shift nuclear magnetic resonance (NMR) is an area of high interest. The aim of this contribution is to describe briefly how this technique has evolved, where it is now and what could be the next challenges in the amazing adventure of the development and application of pure shift NMR experiments.

Insight into old and new pure shift nuclear magnetic resonance methods for enantiodiscrimination

“…In the recent years, pure shift NMR has become a very powerful tool to overcome the resolution problem in 1 H spectra . Pure shift NMR spectroscopy, also known as broadband homonuclear decoupled NMR spectroscopy, suppresses the homonuclear proton‐proton scalar couplings to produce NMR spectra that have only chemical shift, with no multiplet structures.…”

“…Data chunking approach employs a pseudo‐2D type of data acquisition—a series of free induction decays (FIDs) are recorded with carefully chosen chemical shift evolution and J ‐refocusing. The first part (at the center of which J ‐refocuses) of these recorded FIDs are cut out and concatenated to reconstruct a fully decoupled FID . In real time mode, J ‐refocusing element (say, for example, BIRD block) is applied periodically during the acquisition in a single FID .…”

“…However, it is prone to chunking artifact and leads to broader lines due to relaxation decay during the decoupling blocks. PSYCHE in 1D mode can be implemented by using only data chunking approach . Real time decoupling is not applicable to PSYCHE because it refocuses only a fraction of the total excited magnetization.…”

“…The data are collected in a conventional 2D matrix with an incremented evolution time. A homodecoupled FID is constructed by concatenating a chunk from each of the individual 2D time domain signals . The Fourier transform of the reconstructed FID ensures a pure shift 1 H spectrum.…”

“…In case chemical shift difference is in the order of 4–6 Hz, the above‐discussed RES‐TOCSY 2D experiment can be utilized . Though the experiment provides good results, it retains only approximately 1–5% of the sensitivity of a regular 1 H NMR spectrum …”