Thermodynamic, Physical, and Structural Characteristics in Layered Hybrid Type (C2H5NH3)2MCl4 (M = 59Co, 63Cu, 65Zn, and 113Cd) Crystals

The thermal, physical, and molecular dynamics of layered hybrid type (C2H5NH3)2MCl4 (M = 59Co, 63Cu, 65Zn, and 113Cd) crystals were investigated by thermogravimetric analysis (TGA) and magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The temperatures of the onset of partial thermal decomposition were found to depend on the identity of M. In addition, the Bloembergen–Purcell–Pound curves for the 1H spin-lattice relaxation time T1ρ in the rotating frames of CH3CH2 and NH3, and for the 13C T1ρ of CH3 and CH2 were shown to exhibit minima as a function of the inverse temperature. These results confirmed the rotational motion of 1H and 13C in the C2H5NH3 cation. Finally, the T1ρ values and activation energies Ea obtained from the 1H measurements for the H‒Cl···M (M = Zn and Cd) bond in the absence of paramagnetic ions were larger than those obtained for the H‒Cl···M (M = Co and Cu) bond in the presence of paramagnetic ions. Moreover, the Ea value for 13C, which is distant from the M ions, was found to decrease upon increasing the mass of the M ion, unlike in the case of the Ea values for 1H.

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Chemical shift and spin–lattice relaxation time for two crystallographically inequivalent 133 Cs sites in Cs 2 B Br 4 ( B = 57 Co, 63 Cu, and 65 Zn) using magic-angle spinning nuclear magnetic resonance

Solid State Sciences ◽

10.1016/j.solidstatesciences.2017.03.013 ◽

2017 ◽

Vol 67 ◽

pp. 93-98 ◽

Cited By ~ 2

Author(s):

Ae Ran Lim ◽

Sun Ha Kim

Keyword(s):

Nuclear Magnetic Resonance ◽

Relaxation Time ◽

Chemical Shift ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Magic Angle Spinning ◽

Spin Lattice Relaxation ◽

Magic Angle ◽

Spin Lattice ◽

Angle Spinning

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The Effect of O2 Intercalation on the Rotational Dynamics and the Ordering Transition of C60

MRS Proceedings ◽

10.1557/proc-359-505 ◽

1994 ◽

Vol 359 ◽

Cited By ~ 5

Author(s):

S. A. Myers ◽

R. A. Assink ◽

J. E. Schirber ◽

D. A. Loy

Keyword(s):

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Magic Angle Spinning ◽

Rotational Dynamics ◽

Spin Lattice Relaxation ◽

Main Peak ◽

Magic Angle ◽

Spin Lattice ◽

Angle Spinning ◽

Ordering Transition

ABSTRACTWe have used 13C magic-angle spinning (MAS) nuclear magnetic resonance (NMR) to characterize the structure and rotational dynamics of C60 containing oxygen molecules located in the interstitial sites of the fcc lattice. Under normal conditions, a narrow peak at 143.7 ppm is observed for C60. When exposed to oxygen at moderate pressures, several additional resonances appear in the 13C MAS NMR spectrum. These secondary resonances are shifted downfield from the main peak at 143.7 ppm and are due to the Fermi-contact interaction of the paramagnetic oxygen molecules with the 13C nuclear spins. The presence of oxygen depresses the orientational ordering transition by ca. 20 K as observed by DSC. The spin-lattice relaxation time (T1) of each secondary peak shows a minimum near the ordering transition, indicating that this transition is not dependent on the number of oxygen molecules surrounding an individual C60 molecule. The T1 due to paramagnetic relaxation, normalized by the number of surrounding oxygen molecules, is constant. This observation demonstrates that within a given sample, the dynamics of C60 molecules are independent of the number of surrounding oxygen molecules.

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Pulse Shaped Dynamic Nuclear Polarization Under Magic Angle Spinning

10.26434/chemrxiv.9788471.v1 ◽

2019 ◽

Cited By ~ 1

Author(s):

ASIF EQUBAL ◽

Kan Tagami ◽

Songi Han

Keyword(s):

Electron Spin ◽

Lattice Relaxation ◽

Magic Angle Spinning ◽

Spin Lattice Relaxation ◽

Magic Angle ◽

Total Electron ◽

Spin Lattice ◽

Maximum Benefit ◽

Selective Saturation ◽

Angle Spinning

In this paper, we report on an entirely novel way of improving the MAS-DNP efficiency by shaped μw pulse train irradiation for fast and broad-banded (FAB) saturation of the electron spin resonance. FAB-DNP achieved with Arbitrary Wave Generated shaped μw pulse trains facilitates effective and selective saturation of a defined fraction of the total electron spins, and provides superior control over the DNP efficiency under MAS. Experimental and quantum-mechanics based numerically simulated results together demonstrate that FAB-DNP significantly outperforms CW-DNP when the EPR-line of PAs is broadened by conformational distribution and exchange coupling. We demonstrate that the maximum benefit of FAB DNP is achieved when the electron spin-lattice relaxation is fast relative to the MAS frequency, i.e. at higher temperatures and/or when employing metals as PAs. Calculations predict that under short T<sub>1e </sub>conditions AWG-DNP can achieve as much as ~4-fold greater enhancement compared to CW-DNP.

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