SIMPSON: a general simulation program for solid-state NMR spectroscopy.

The reaction of triphenylphosphine or N-butylimidazole with cyclic sultones gives zwitterions that are subsequently converted into ionic liquids by reaction with trifluoromethane sulfonic acid or p-toluenesulfonic acid. The resulting ionic liquids have cations to which are tethered alkane sulfonic acid groups. These Bronsted acidic ionic liquids are useful solvent/catalysts for several organic reactions, including Fischer esterification, alcohol dehydrodimerization and the pinacol rearrangement. The new ionic liquids combine the low volatility and ease of separation from product normally associated with solid acid catalysts, with the higher activity and yields normally found using conventional liquid acids.

Novel Brønsted Acidic Ionic Liquids and Their Use as Dual Solvent−Catalysts

Advanced solid-state NMR methods for the elucidation of structure and dynamics of molecular, macromolecular, and supramolecular systems.

We describe an efficient method for the recovery of homonuclear dipole–dipole interactions in magic‐angle spinning NMR. Double‐quantum homonuclear rotary resonance (2Q‐HORROR) is established by fulfilling the condition ωr=2ω1, where ωr is the sample rotation frequency and ω1 is the nutation frequency around an applied resonant radio frequency (rf) field. This resonance can be used for double‐quantum filtering and measurement of homonuclear dipolar interactions in the presence of magic‐angle spinning. The spin dynamics depend only weakly on crystallite orientation allowing good performance for powder samples. Chemical shift effects are suppressed to zeroth order. The method is demonstrated for singly and doubly 13C labeled L‐alanine.

Double‐quantum homonuclear rotary resonance: Efficient dipolar recovery in magic‐angle spinning nuclear magnetic resonance

High-Field and High-Speed CP-MAS13C NMR Heteronuclear Dipolar-Correlation Spectroscopy of Solids with Frequency-Switched Lee–Goldburg Homonuclear Decoupling

Frequency-switched pulse sequences: Homonuclear decoupling and dilute spin NMR in solids

Frequency-Switched Lee—Goldburg Sequences in Solids

High-resolution 1H NMR in solids with frequency-switched multiple-pulse sequences

The development of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy for intact tissue analysis and the correlations between the measured tissue metabolites and disease pathologies have inspired investigations of slow-spinning methodologies to maximize the protection of tissue pathology structures from HR-MAS centrifuging damage. Spinning sidebands produced by slow-rate spinning must be suppressed to prevent their complicating the spectral region of metabolites. Twenty-two human prostatectomy samples were analyzed on a 14.1T spectrometer, with HR-MAS spinning rates of 600 Hz, 700 Hz, and 3.0 kHz, a repetition time of 5 sec, and employing various rotor-synchronized suppression methods, including DANTE, WATERGATE, TOSS, and PASS pulse sequences. Among them, DANTE, as the simplest scheme, has shown the most potential in suppression of tissue water signals and spinning sidebands, as well as in quantifying metabolic concentrations.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/mrm.10562

Anthony Bielecki

Papers

Frequency-switched pulse sequences: Homonuclear decoupling and dilute spin NMR in solids

Frequency-Switched Lee—Goldburg Sequences in Solids

High-resolution 1H NMR in solids with frequency-switched multiple-pulse sequences

High-resolution magic angle spinning proton NMR analysis of human prostate tissue with slow spinning rates.

Using a cross-coil to reduce RF heating by an order of magnitude in triple-resonance multinuclear MAS at high fields.