High-Resolution Nuclear Magnetic Resonance Spectroscopy

Abstract

The rapid development of NMR spectroscopy has been characterized by a succession of discrete, significant advances in instrumentation, as well as by less dramatic but cumulatively important improvements in instrument performance, experimental techniques, spectral analysis, and theory. Most significant are the advances in magnet technology, which within 13 years increased the available field strengths from 7.04 to 51.7 kilogauss (with corresponding increase in the PMR frequency from 30 to 220 megahertz). Great improvements in spectrometer stability and in the coupling of spectrometers with on-line computers have so improved sensitivity that some nuclei possessing less favorable NMR characteristics can now be studied.

The reaction of an iridium PNP complex with parahydrogen facilitates polarisation transfer without chemical change

“…Reactions of [(C 5 H 3 N(CH 2 P( t Bu) 2 ) 2 )Ir(H) 2 ( py)]BF 4 (4) with parahydrogen Under these conditions, when a sample of 1 containing pyridine is placed under p-H 2 and monitored by high field 1 H NMR spectroscopy at 298 K the hydride signals of 4 show PHIP (Fig. 2a).…”

“…It actually involves the detection of these reaction products and relies on the fact that some of the newly introduced p-H 2 derived spin order is preserved in the transformation. [12][13][14] Such inorganic hydrogen addition products have yielded 1 H NMR signals that reflect a 100% polarization level and are therefore 31 000 times larger than those normally visible when observed at 9.4 Tesla. 15 In this study we utilize the reaction of 2,6-bis(di-tert-butylphosphinomethyl)-pyridine with [IrCl(COD) 2 ]BF 4 (COD = cyclooctadiene) to prepare the known PNP pincer 16,17 complex [(C 5 H 3 N(CH 2 P( t Bu) 2 ) 2 )IrH(C 8 H 11 )(NCCH 3 )]BF 4 (1) 18 (Scheme 1) and then explore its potential to act as a catalyst for signal amplification by reversible exchange (SABRE).…”

“…Nuclear magnetic resonance (NMR) spectroscopy finds widespread use in both chemistry and medicine despite the fact that it suffers from inherent low sensitivity due to the small energy differences that exist between the nuclear spin state orientations it probes. 1 The net effect of this situation is that only 1 out of every 31 000 hydrogen atoms present in the sample contribute positively to the resulting signal in a room temperature 1 H NMR spectrum that is recorded at 400 MHz (9.4 Tesla (T)). This challenge has resulted in the development of hyperpolarization methods to redistribute the nuclear spin state populations such that dramatically increased sensitivity is achieved.…”

NMR in Chemistry--An Evergreen

“…Earlier, such studies were hampered by inadequate sensitivity and overlap of the many resonances belonging to various nonequivalent but similar protons. In this connection, the introduction of high frequency, high resolution proton spectrometers using superconducting magnets was a major advance, as discussed by Ferguson & Phillips in their 1967 review (49). Moreover, Phillips and co-workers demonstrated that high field, high resolution NMR is ideally suited to investigate the structure and interaction of nucleic acids and proteins in solution and predicted that it would contribute greatly in the future to a better understanding of the highly specific biological functions of these complex molecules.…”

Emerging theories and technologies on computational imaging

“…For example, the synthetic aperture technique (Ryle, 1972) applied in radio telescopes and computed tomography (Brenner and Hall, 2007) makes full use of high computation power and reconstructs highdimensional and high-resolution information from a large amount of its low-dimensional or low-resolution sampling successfully. This computational imaging strategy is applied frequently and has contributed significantly to the imaging field; high-resolution nuclear magnetic resonance spectroscopy is a typical example (Ferguson and Phillips, 1967).…”