Analytical Instrument Documents

The ROSY (Relaxation Ordered SpectroscopY) is a method in which the 13C CPMAS spectrum of a mixture is classified by a longitudinal relaxation time of 1H, and the 13C CPMAS spectrum is displayed separately for each substance. In solution NMR, each peak in the 1H spectrum has its own longitudinal relaxation time. In solid-state NMR, however, spin diffusion occurs due to the dipolor interaction between 1H, and all 1H have the same longitudinal relaxation in the domain within a certain distance. The 13C spectrum can be separated for each domain by using this difference in relaxation time of 1H. The longitudinal relaxation time (T1H) obtained by the saturation recovery method as shown in Fig.1a is usually used to separate the 13C spectrum of the mixture. The size of the domain that can be separated by this method is about 100 nm. To separate domains smaller than this, a measurement using the relaxation time at rotational flame (T1ρH) obtained by the spinlock method as shown in Fig.1b is effective. The domain size that can be separated by T1ρH is about several nm, and it is possible to determine the phase separation structure of block copolymers and the molecular compatibility.

Diffusion-ordered spectroscopy (DOSY) is a powerful NMR method for the analysis of mixtures. In DOSY, signals in the NMR spectrum are resolved according to the measured diffusion coefficient for each signal, yielding a 2D spectrum which has chemical shift along the x-axis and diffusion coefficient along the y-axis.

NOE (Nuclear Overhauser Effect) correlations  comprise important information to estimate internuclear distance and determine structure. However, NOE correlation peaks are very weak compared with diagonal peaks in 2D NOESY. For this reason, it is difficult to observe NOE correlation peaks in the vicinity of much larger diagonal peaks.

The ROYALPROBE™ HFX can simultaneously irradiate 1H, 19F, and 13C (or other X-nuclei) even in a basic console with basic two-channel console, and is a versatile probe that can measure a wide-variety of nuclei at high sensitivity. Here we introduce some useful experiments for fluorine-containing compounds that can be run on conjunction with JNM-ECZ400S equipped with ROYALPROBE™ HFX.

1H, in principle, is very useful nucleus to investigate atomic-resolution structures and dynamics due to its high abundance (>99%) and gyromagnetic ratio (600 MHz at 14.1T). In fact 1H is the first choice of nucleus in solution NMR. On the other hand, 1H NMR of rigid solids is much less common. This is because 1H solid-state NMR gives very broad (~50 kHz) and featureless spectra (Fig 1a) due to strong 1H-1H dipolar coupling, which is dynamically averaged out in solution. Magic angle spinning (MAS) removes the broadening to the first order, but is not enough to achieve high resolution 1H NMR at moderate MAS rate (Fig 1b). Tremendous efforts were made to overcome this issue from the early dates of solid-state NMR towards high-resolution 1H NMR [1]. Most of them combine MAS with sophisticated 1H pulses which is dubbed CRAMPS (combined rotation and multiple pulse spectroscopy). Nowadays very fast MAS > 60 kHz can be used to achieve high-resolution 1H solid-state NMR (Fig 1c) [2]. However, the traditional CRAMPS is still useful as that can be performed with very conventional solid-state NMR equipment, for example 4 mm MAS probe with a 400 MHz spectrometer. Moreover, wPMLG at moderate MAS rate often overwhelms fast MAS in terms of resolution. In this note, we will describe tutorial guidance to optimize experimental parameters for CRAMPS.

Multidimensional correlation NMR spectroscopies, which provides inter-nuclear proximity/connectivity, play a crucial role to probe the atomic resolution structures. Especially, 1H-1H homonuclear correlation spectroscopy is quite useful source of information because of high abundance (>99%) and gyromagnetic ratio, thus resulting in strong inter nuclear interactions. Thanks to the development of high resolution 1H solid-state NMR, now it is feasible to observe 1H-1H correlation high resolution solid-state NMR [1]. There are two distinctive categories; 1) single quantum (SQ)/SQ correlation and 2) double quantum (DQ)/SQ correlations. In this note we introduce 2D 1H SQ/ 1H SQ and 1H DQ/ 1H SQ correlation spectroscopy to probe the internuclear proximity using high-resolution 1H solid-state NMR techniques.

Lithium ion secondary batteries using spinel-type lithium titanium oxide (LTO) as the negative electrode material are excellent in safety and cycle characteristics due to their chemical stability, and have already been put into practical use.

In comparison with the UltraCOOL probe, SuperCOOL probe represents a cryogenic probe with high sensitivity at lower cost and power consumption. Thermal noise reduction due to new designed cooling system greatly enhances the sensitivity of NMR measurement.

It is often difficult to unambiguously determine structures of molecules, which have many non-protonated carbon atoms. Because such compounds contain quaternary carbons, lack protons and bonding to quaternary carbons each other, HMBC (Heteronuclear Multiple Bond Correlation) experiment cannot provide long-range 1H-13C connectivity. Therefore, INADEQUATE (Incredible Natural Abundance DoublE QUAntum Transfer Experiment), which is 13C-13C correlation experiment at natural 13C abundance, represents a powerful tool for proton-diluted compounds.

Here, we combine ED and solid-state NMR through the first principle quantum computation with the NMR crystallography approach for crystalline structure solution. The method, electron and NMR nano-crystallography, can be applied to nano- to micro-crystals even for mixture samples.