JEOL Resources

The magnetic field dependence of the one-dimensional spectrum and MQMAS spectrum of half-integer quadrupolar nuclei

Tue, 15 Apr 2025 09:29:54 GMT

NM250001E

1 D spectrum

For a spin with spin quantum number I, there are 2I+1 energy levels and 2I possible single-quantum transitions. In most cases, these single-quantum transitions are observed in NMR. The transitions between the ±1/2 levels of half-integer spins (I = 3/2, 5/2, 7/2, 9/2) are called central transitions (CT), while other transitions are called satellite transitions (ST). ST undergoes first-order quadrupolar perturbation, causing the signal to broaden in the MHz range. In contrast, CT only undergoes second-order quadrupolar perturbation and the signal is distributed over a narrower range than ST. ST signals are broad, have lower sensitivity, and often exhibit more complex patterns. Therefore, in the case of half-integer quadrupolar nuclei, CT signals are mostly observed and analyzed.

Figure 1. The ²³Na one-dimensional spectrum of Na₄P₂O₇ shows that the ST signals are distributed over a very wide range (left), with low sensitivity and complex signal patterns. In contrast, the CT signals are distributed over a narrower range and have higher sensitivity (right).

* denotes the background signal of ⁶³Cu from the coil.

The linewidth of the CT signals (in Hz) is proportional to the inverse of the resonance frequency, and therefore, the resolution (in ppm) is proportional to the square of the inverse of the resonance frequency. Since the resonance frequency is proportional to the strength of the magnetic field, using a stronger magnetic field results in sharper and higher-resolution spectra. However, in many cases, it is difficult to completely separate the signals even with a high magnetic field.

Figure 2. Na₄P₂O₇ ²³Na spectra, Magnetic field dependence of CT signals: By using a high-field instrument, the signals become relatively sharper. and the resolution is improved.

MQMAS spectrum

The technique of MQMAS (Multiple Quantum Magic Angle Spinning) provides a high-resolution spectrum with the Isotropic shift on the vertical axis. The Isotropic shift axis combines two pieces of information: chemical shift and the magnitude of the quadrupolar interaction. Therefore, unlike typical NMR two-dimensional measurements (such as COSY, HMQC, etc.), the position of the signal along the vertical axis (in ppm) changes with the magnetic field. Fig. 3 shows the ²³Na MQMAS spectra of Na₄P₂O₇ obtained at multiple magnetic fields. It can be seen that the signal position along the vertical axis changes, and this change is nonlinear.

Figure 3. The ²³Na MQMAS spectra of Na₄P₂O₇, obtained under magnetic field strengths of 400, 500, 600, 700, and 800 MHz, from left to right.

In the Isotropic axis of MQMAS, a larger magnetic field does not necessarily result in better signal separation. Note that multiple signals may overlap on the Isotropic axis, or the signal positions may be swapped when different magnetic fields are used. For a rigorous analysis, it is advisable to acquire and compare MQMAS spectra of the same sample at multiple magnetic fields. Fig. 4 shows the ⁸⁷Rb MQMAS spectra of RbNO₃ obtained at several magnetic fields. This sample contains three different chemical species of ⁸⁷Rb, but at 500 MHz, two of the signals overlap. Additionally, at 400 MHz and 600, 700 MHz, the signal positions are swapped.

Figure 4. The ⁸⁷Rb MQMAS spectra of RbNO₃, obtained under magnetic field strengths of 400, 500, 600, 700, and 800 MHz, from left to right.

Reference

Duer, M. J. (Ed.). (2001). Solid‐State NMR Spectroscopy: Principles and Applications. Blackwell Science Ltd

Structural Analysis of histidine hydrochloride monohydrate Using Ultrafast MAS

Tue, 15 Apr 2025 09:16:19 GMT

NM240010E

Ultrafast MAS

In solid-state NMR, interactions such as dipolar couplings and chemical shift anisotropy often result in extremely broad and low-sensitivity spectra in the stationary state. To address this issue, the sample is tilted at an angle of 54.74 degrees relative to the magnetic field and spun rapidly, creating a state similar to that of a solution. This technique, called MAS (Magic Angle Spinning), improves both resolution and sensitivity. For experiments observing ¹³C, a spinning speed of a few kHz is sufficient to average out heteronuclear dipolar interactions between ¹H and ¹³C, and combined with ¹H decoupling, spectra suitable for analysis can be obtained. However, homonuclear dipolar interactions, such as those between ¹H nuclei, are stronger and require even higher spinning speeds for effective averaging. Recent advances in hardware have enabled spinning speeds exceeding 70 kHz, making ¹H spectra useful for analysis in solid-state NMR. Figure 1 illustrates one-dimensional spectra of glycine acquired at spinning speeds ranging from 20 kHz to 110 kHz, demonstrating how high-speed spinning achieves higher resolution and sensitivity. This article presents an example of detailed structural analysis of histidine hydrochloride monohydrate using ultrafast MAS.

Figure 1. Structure of Glycine in the crystalline state and spinning speed dependence of its ¹H spectrum

¹H 1 D measurement

With high-resolution ¹H spectra obtained through high-speed MAS, quantitative discussions become feasible. Fig. 2 shows the one-dimensional ¹H spectrum of histidine hydrochloride monohydrate along with the integral values for each signal. Although some overlap between signals introduces errors, it is possible to correlate the integral values with the number of hydrogen atoms for the five signals, assigning 1, 1, 5, 2, and 3 hydrogens, respectively.

Figure 2. The one-dimensional ¹H spectrum of histidine hydrochloride monohydrate, with the background reduced using DEPTH2.

¹H-¹³C 2 D measurement

By acquiring a ¹H-¹³C correlation spectrum, information about the proximity between ¹H and ¹³C nuclei can be obtained. Figure 3 shows the ¹H-¹³C HSQC spectrum. Here, the transfer of magnetization from ¹H to ¹³C was achieved using the Cross Polarization (CP) method. To detect signals corresponding to direct CH bonds, the contact time for magnetization transfer was set to 0.2 ms. The spectrum reveals signals for two imidazole CH, aliphatic CH and CH₂ groups, demonstrating that the aliphatic CH and CH₂ signals overlapped in the one-dimensional ¹H spectrum. Additionally, by increasing the contact time, it is possible to observe correlation signals over longer distances.

Figure 3. ¹H-¹³C spectrum of histidine hydrochloride monohydrate

¹H-¹⁴N 2 D measurement

By acquiring a ¹H-¹⁴N correlation spectrum, information about the proximity between hydrogen and nitrogen atoms can be obtained. Figure 4 shows the ¹H-¹⁴N T-HMQC spectrum. The interpretation of this spectrum is similar to that of the ¹H-¹³C HSQC spectrum, but here, the transfer of magnetization from ¹H to ¹⁴N was achieved using a different method called TRAPDOR. Three signals were detected: one corresponding to the NH₃⁺ group and two signals corresponding to the NH groups in the imidazole ring.

Figure 4. ¹H-¹⁴N spectrum of histidine hydrochloride monohydrate

¹H-³⁵Cl 2 D measurement

By acquiring a ¹H-³⁵Cl correlation spectrum, information about the proximity between hydrogen and chlorine atoms can be obtained. Figure 5 shows the ¹H-³⁵Cl DQ T-HMQC spectrum. The interpretation of this spectrum is similar to that of the ¹H-¹³C HSQC and ¹H-¹⁴N T-HMQC spectra, but a different measurement technique is used here. Since there is only one type of chlorine atom, only a single signal is observed along the vertical axis. However, this allows determination of which hydrogen atoms are in close proximity to the chlorine atom.

Figure 5. ¹H-³⁵Cl spectrum of histidine hydrochloride monohydrate

Assignment of signals

The projection spectra of the ¹H one-dimensional spectrum and three projection spectra of two-dimensional experiments shown thus far are presented in Fig. 6. From the ¹H-¹³C spectrum, the imidazole CH and CH, CH₂ signals are assigned. Then, from the ¹H-¹⁴N spectrum, the signals of two imidazole NH and NH₃⁺ are assigned. Additionally, the signal that does not show correlation with either C or N is identified as the H₂O signal. In this way, it is possible to assign signals by combining information from several two-dimensional spectra.

Figure 6. The projection spectra of the ¹H one-dimensional spectrum and three two-dimensional correlation spectra of histidine hydrochloride monohydrate.

¹H-¹H Correlation spectrum (DQMAS)

Fig. 7 shows the ¹H-¹H correlation spectrum. Correlation signals are detected between two adjacent ¹H atoms. In the DQMAS spectrum, the vertical axis represents the DQ (double quantum) shift, and correlation signals appear at positions symmetric to a line with a slope of 2. An example of the analysis is shown below. Focusing on the NH signal of the imidazole ring on the far left (red in the figure), five correlations are detected, indicated by red lines. These are correlation signals between the H atoms on the imidazole ring and water molecules. Similarly, focusing on the NH signal of the second imidazole ring from the left (yellow in the figure), correlation signals between the H atoms on the imidazole ring and water molecules are also detected. Although influenced by the molecular mobility, proximity information within approximately 2-3 Å can be obtained.

Figure 7. ¹H DQMAS spectrum of Histidine hydrochloride monohydrate. A detailed analysis was performed on the two imidazole NH groups.

Reference

Nishiyama, Y., Endo, Y., Nemoto, T., Utsumi, H., Yamauchi, K., Hioka, K., & Asakura, T. (2011). Journal of Magnetic Resonance, 208(1), 44–48.
Jarvis, J. A., Haies, I. M., Williamson, P. T. F., & Carravetta, M. (2013). Phys. Chem. Chem. Phys., 20.
Hung, I., & Gan, Z. (2020). J. Phys. Chem. Lett., 11(12).
Saalwächter, K., Lange, F., Matyjaszewski, K., Huang, C.-F., & Graf, R. (2011). Journal of Magnetic Resonance, 212(1), 204–215.

Solid State Battery Note

Tue, 05 Mar 2024 09:57:55 GMT

Battery cells are essential in modern life as they are extensively used in mobile phones, personal computers, and even in automobiles as the power source in recent years.
The shift to battery vehicles (BEV) is rapidly advancing worldwide in order to achieve carbon neutrality by 2050 which is to “reduce overall greenhouse gas emissions to zero”. The research and development on rechargeable battery cells that can be used repeatedly, are progressing for the use of power source of BEV and larger energy storage system (ESS). To improve both the performance and quality of these battery cells, analyses and evaluations by using various high-performance evaluation instruments are required.
JEOL offers a wide variety of analytical instruments available for morphological observations, surface analyses, structure analyses, and chemical analyses at micro- to nano-scales for the purpose of research, development, and quality improvement.
This Solid-state battery Note has been created with the samples provided by Prof. Atsunori Matsuda, Toyohashi University of Technology (Department of Electrical and Electronic Information Engineering), to provide solutions and reference information for research and development of solid-state batteries evolving from the lithium ion batteries (LIBs).

Chenometric Tool - Gateway to Chenometrics with NMR Data

Thu, 24 Aug 2023 07:44:26 GMT

Applications note NM220007

Chenometrics is a discipline that utilizes data mining techniques, including dimensionality reduction, discrimination, visualization, and regression, to extract information from extensive sets of experimental analytical data. NMR spectroscopy, a highly quantitative and reproducible technique, allows for non-invasive analysis of chemical species with minimal sample preparation. This is particularly advantageous for data mining, as NMR spectra, including series of ¹H NMR spectra of biological samples, are commonly employed as input for multivariate analysis by converting series of 1D NMR spectra into a matrix. The 'Chemospec' package in the R language for statistical computing serves as the engine for multivariate analysis. When the 'Chempspec' package is installed, the Delta software offers a seamless user interface for exploratory multivariate analysis.

Diffusion Analysis Multi - Multiple Exponential Function Fitting for PFG-NMR data

Thu, 24 Aug 2023 07:32:59 GMT

Applications note NM220006E

Pulsed-Field Gradient Nuclear Magnetic Resonance (PFG-NMR) is utilized to analyze the self-diffusion of molecules and ions. The self-diffusion coefficient (D) in PFG-NMR is determined by recording the decay of signal intensity through a series of experiments using either Pulsed Gradient Spin Echo (PGSE) or Pulsed Gradient Stimulated Echo (PGSTE) sequences with varying gradient strengths (G). The decay of signal intensity is subsequently analyzed using curve fitting or inverse Laplace transformation methods. The Delta NMR software provides a curve analysis tool that supports the fitting of PFG-NMR data. Versions 5.3.3 and earlier of the Delta NMR software support curve fitting using a model that assumes a single self-diffusion coefficient contributing to the decay. However, starting from the Delta NMR software version 6.0 and onwards, there is support for curve fitting using the "Diffusion Analysis Multi" feature. This feature enables the analysis to account for multiple self-diffusion coefficients during the curve fitting process.

Double Stimulated Echo (DSTE) Experiments for Thermal Convection Compensation in PFG-NMR

Thu, 24 Aug 2023 07:21:27 GMT

Applications note NM220005

Pulsed-Field Gradient NMR (PFG-NMR) is utilized for analyzing the self-diffusion of molecules and ions, which are commonly referred to as 'particles' in this context. The translation of particles by thermal convection significantly impacts the decay curve in PFG-NMR experiments, particularly when dealing with solution and liquid samples. In cases where the convection-induced translation is substantial, the decay curve exhibits a cosine-like behavior, leading to an apparent increase in the self-diffusion coefficient compared to the actual value. Additionally, the decay curves may become distorted, occasionally resulting in the appearance of signals in negative phase. To address this convection artifact in PFG-NMR, Double Stimulated Echo (DSTE) experiments are specifically designed and employed.

Multiple-Resonance Measurements on ECZ Luminous_NM220004E

Mon, 24 Oct 2022 09:53:29 GMT

Fig. 2 shows an example of ¹H, ¹³C, and ³¹P triple resonance measurement when using an HCX triple-resonance probe. As shown in Fig 2 b), the doublets collapse into singlets by the simultaneous ¹H and ³¹P decoupling. This increases sensitivity and makes the analysis of the spectrum easier. Fig. 3 shows an example of ¹H, ¹³C and ¹⁵N triple-resonance measurement performed on a labeled protein using an HCN triple-resonance probe. Both triple-resonance measurements were performed on a standard 2-channel JNM-ECZL600G instrument. It is clear that the triple-resonance measurements were properly performed.

Fig. 2: a) ¹³C{1H} and b) ¹³C{1H}{³¹P} spectra of diethylmethylphosphonate in CDCl₃ by HCX probe

Fig. 3: 3D HNCOCO spectrum of ¹³C/¹⁵N labeled Ubiquitin in 90% H₂O / 10% D₂O by HCN probe

Introduction of a method to analyze 3D structures using homonuclear couplings_NM210004E

Mon, 29 Nov 2021 10:14:39 GMT

Structural analysis by NMR can provide not only a planar molecular structure but also three-dimensional structural information. In this Note, we describe a method for obtaining information on dihedral angles by using ¹H-¹H coupling constants (J_HH values). For example, hydrogen atoms attached to a cyclohexane ring are either located in axial or equatorial positions in respect to the cyclohexane ring (Fig. 1). The dihedral angles between vicinal protons are known to be ∠H_ax-C-C-H_ax ≈ 180°, ∠H_ax-C-H_eq ≈ 60°, and ∠H_eq-C-C-H_eq ≈ 60°. If we look at the Karplus curve shown in Fig. 2, we can see that ³J_HH of around 4 Hz can be expected in the case of the dihedral angle of 60°, while ³J_HH of around 13 Hz corresponds to the dihedral angle of 180°. In reality, ³J_HH values depend on substituents attached to the cyclohexane ring in substituted cyclohexanes, so the analysis is not straightforward, but the basic trend of having a larger J-value for a 180° dihedral angle compared to a 60° dihedral angle remains unchanged. Therefore, from the value of ³J_HH of the methylene protons, it is possible to differentiate between the dihedral angle of 60° or 180°.

Please click below to download and read more.

20 T/m high field gradient strength diffusion measurement system_NM210006E

Mon, 29 Nov 2021 09:35:34 GMT

Diffusion measurement of Lithium ions in solid electrolyte

Since the ⁷Li signal of lithium ions in solid electrolyte often has a short T₂ relaxation time, the magnetic field gradient pulse (PFG) width applied to the transverse magnetization cannot be sufficiently long. Since the diffusion coefficients of solid electrolytes are also small, it is necessary to be able to apply a large amplitude of PFG in a short time in order to obtain attenuation of the echo signal due to diffusion.
Fig. 1 shows ⁷Li echo signal decay plots of solid oxide electrolyte LLTZO (D=2.1x10^-13 m²/s @30°C) using 30A (12 T/m) and 50A (20 T/m) magnetic field gradient power supplies. The use of the 50A power supply makes it possible to calculate the diffusion coefficient more accurately and to measure the diffusion of systems with smaller diffusion coefficients.

Sample：	LLTZO single crystal
Instruments：	JNM-ECZ500R, Diffusion probe
Method：	⁷Li Stimulated Echo Diffusion time = 150ms PFG width = 2.5 ms Temperature = 30 °C

Fig. 1 ⁷Li signal decay plots of a single crystal LLTZO as a function of
gradient strength by using 30A and 50A gradient power supplies.

Courtesy of Dr. Naoaki Kuwata (NIMS)
and Dr. Junji Akimoto (AIST)

Lithium Ion Battery Note

Mon, 27 Jul 2020 21:13:53 GMT

The applications for lithium ion batteries (LIB) cover a wide range, from power sources for personal computers and mobile devices to automobiles, and there is always a demand for even better performance and safety. In order to ensure the performance and quality of LIB, analysis and evaluation using high-performance assessment systems is necessary. JEOL offers a full line-up of equipment to support the development of new LIB technologies and to improve product quality, including instruments for morphology observation and surface analysis, chemical analysis systems to perform structural analysis on a molecular level, as well as fabrication systems to create high-performance coatings and powders. This LIB note offers solutions for researchers and engineers who are looking for the best equipment for their application.

JEOL Resources

The magnetic field dependence of the one-dimensional spectrum and MQMAS spectrum of half-integer quadrupolar nuclei

NM250001E

1 D spectrum

MQMAS spectrum

Reference

Structural Analysis of histidine hydrochloride monohydrate Using Ultrafast MAS

NM240010E

Ultrafast MAS

1H 1 D measurement

1H-13C 2 D measurement

1H-14N 2 D measurement

1H-35Cl 2 D measurement

Assignment of signals

1H-1H Correlation spectrum (DQMAS)

Reference

Solid State Battery Note

Chenometric Tool - Gateway to Chenometrics with NMR Data

Diffusion Analysis Multi - Multiple Exponential Function Fitting for PFG-NMR data

Double Stimulated Echo (DSTE) Experiments for Thermal Convection Compensation in PFG-NMR

Multiple-Resonance Measurements on ECZ Luminous_NM220004E

Introduction of a method to analyze 3D structures using homonuclear couplings_NM210004E

Please click below to download and read more.

20 T/m high field gradient strength diffusion measurement system_NM210006E

Diffusion measurement of Lithium ions in solid electrolyte

Lithium Ion Battery Note

¹H 1 D measurement

¹H-¹³C 2 D measurement

¹H-¹⁴N 2 D measurement

¹H-³⁵Cl 2 D measurement

¹H-¹H Correlation spectrum (DQMAS)