Related Experiment Video
Updated: Apr 17, 2026
13:56
Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations
Published on: October 12, 2019
8.5K
Solid-state dynamics in the closo-carboranes: a (11)B MAS NMR and molecular dynamics study
Hernán Ahumada1,2, Teresa Kurkiewicz1,3, Michael J Thrippleton1,4
1†School of Chemistry and WestCHEM, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
The Journal of Physical Chemistry. B
|February 25, 2015
Summary
This study reveals dynamic behaviors of closo-carborane isomers using solid-state NMR and molecular dynamics. It confirms phase transitions and anisotropic molecular reorientation at different temperatures.
Area of Science:
- Solid-state chemistry
- Materials science
- Nuclear Magnetic Resonance spectroscopy
Background:
- Closo-carboranes (C2B10H12) are a class of boron-containing compounds with unique structural and dynamic properties.
- Understanding their dynamic behavior is crucial for applications in materials science and supramolecular chemistry.
Purpose of the Study:
- To investigate the dynamic behavior of the three closo-carborane isomers (C2B10H12) across various temperatures.
- To correlate experimental solid-state NMR data with theoretical molecular dynamics simulations.
Main Methods:
- Solid-state magic angle spinning (MAS) Nuclear Magnetic Resonance (NMR) techniques, specifically (11)B MAS and (11)B MQMAS NMR.
- Molecular dynamics (MD) simulations to calculate rotational correlation times (τc) and analyze molecular reorientation.
Main Results:
- At high temperatures, narrow (11)B MAS line widths and picosecond-scale rotational correlation times indicate quasi-isotropic rotation.
- Discontinuities in (11)B spin-lattice relaxation times (T1) confirm phase changes at lower temperatures.
- Broader (11)B MAS lines at low temperatures suggest anisotropic molecular reorientation, supported by reduced quadrupolar parameter (PQ(eff)) values.
Conclusions:
- The study elucidates the temperature-dependent dynamic behavior of closo-carborane isomers.
- Experimental NMR findings are consistent with MD simulations, revealing transitions from quasi-isotropic to anisotropic molecular reorientation.
- For p-carborane, low-temperature reorientation occurs around the C5 symmetry axis, as supported by simulations.
More Related Videos
Related Concept Videos
01:08NMR Spectroscopy: Spin–Spin Coupling
3.9K
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved...
3.9K
02:54Molecular and Ionic Solids
21.1K
Crystalline solids are divided into four types: molecular, ionic, metallic, and covalent network based on the type of constituent units and their interparticle interactions.
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
21.1K
01:17Spin–Spin Coupling: One-Bond Coupling
1.6K
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
1.6K
01:08Spin–Spin Coupling Constant: Overview
1.7K
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
1.7K
02:18Network Covalent Solids
16.6K
Network covalent solids contain a three-dimensional network of covalently bonded atoms as found in the crystal structures of nonmetals like diamond, graphite, silicon, and some covalent compounds, such as silicon dioxide (sand) and silicon carbide (carborundum, the abrasive on sandpaper). Many minerals have networks of covalent bonds.
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
16.6K
01:30NMR and Mass Spectroscopy of Carboxylic Acids
5.7K
In ¹H NMR spectroscopy, acidic protons (–COOH) of carboxylic acids are highly deshielded and absorb far downfield, at around 9–12 ppm. The chemical shift value depends on the concentration and solvent used.
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the...
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the...
5.7K