Communication: Molecular gears

Burnell, E. Elliott; Lange, C.A. de; Meerts, W. Leo

doi:10.1063/1.4962221

Cited by 10 publications

(9 citation statements)

References 27 publications

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“…The angles α i define the methyl rotation and are shown as zero. Reproduced with permission from ref …”

Section: Resultsmentioning

confidence: 99%

“…Our experimental results therefore shed new light on an old problem. For a full account of this work we refer to the literature ref .…”

Section: Resultsmentioning

confidence: 99%

“…A demonstration of the automatic baseline removal. Experimental and fitted NMR spectra of hexamethylbenzene in 1132 at 298 K . A, Experimental spectrum (1742 scans).…”

Section: Automatic Baseline Removal In Nmr Spectramentioning

confidence: 99%

“…The HMB couplings obtained from the fit are D 1,2 = 1629.4 ± 0.4 Hz, D 1,4 = −456.6 ± 0.2 Hz, D 1,7 = −89.4 ± 0.3 Hz and D 1,10 = −57.1 ± 0.4 Hz. Modified from Figure of ref , reproduced with permission…”

Section: Automatic Baseline Removal In Nmr Spectramentioning

confidence: 99%

“…In the present paper, we shall apply EAs to the extremely complex 1 H NMR spectra of C 12 H 18 (hexamethylbenzene, HMB) and C 6 H 12 (cyclohexane). In both solutes internal motion is important.…”

Section: Introductionmentioning

confidence: 99%

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Evolutionary algorithms and nuclear magnetic resonance of oriented molecules

Burnell

Lange

Dong

et al. 2016

Concepts Magnetic Resonance

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In this article, we discuss the progress achieved with the use of evolutionary algorithms for the analysis of 1 H Nuclear Magnetic Resonance spectra of solutes in orientationally ordered liquids. With these tools the analysis of extremely complex spectra that were hitherto impossible to solve has now become eminently feasible. We discuss applications to 2 molecules of special interest: (a) hexamethylbenzene, which is a text book example of steric hindrance between adjacent rotating methyl groups; and (b) cyclohexane which is the standard example of interconversion between various molecular conformations. New interesting physics is obtained in both cases.cyclohexane, evolutionary algorithms, hexamethyl benzene, liquid crystal, orientational order

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“…The angles α i define the methyl rotation and are shown as zero. Reproduced with permission from ref …”

Section: Resultsmentioning

confidence: 99%

“…Our experimental results therefore shed new light on an old problem. For a full account of this work we refer to the literature ref .…”

Section: Resultsmentioning

confidence: 99%

“…A demonstration of the automatic baseline removal. Experimental and fitted NMR spectra of hexamethylbenzene in 1132 at 298 K . A, Experimental spectrum (1742 scans).…”

Section: Automatic Baseline Removal In Nmr Spectramentioning

confidence: 99%

Section: Automatic Baseline Removal In Nmr Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Evolutionary algorithms and nuclear magnetic resonance of oriented molecules

Burnell

Lange

Dong

et al. 2016

Concepts Magnetic Resonance

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Recent progress in NMR study of liquid-crystal assemblies

Dong

2020

Annual Reports on NMR Spectroscopy

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Magnetically Driven Structural Phase Transition in Hexamethylbenzene

Yen

2018

J. Phys. Chem. C

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The methyl groups in hexamethylbenzene C6(CH3)6 become magnetically ordered at the molecular level below 118 K. This is also near the temperature at which the system structurally transitions from triclinic to a unique near-cubic phase. High-precision measurements of the near-static dielectric constant reveal that the structural phase transition is actually comprised of four successive transformations upon cooling at T1=110.7 K, T2=109.5 K, T3=109.1 K and T4=107.8 K. In contrast to warming, only two transitions occur at T'4=119.2 K and T'1=120.9 K. The methyl groups in the near-cubic phase become slightly distorted according to existing neutron powder diffraction measurements. Analysis of the 2 6 =64 possible spin orientation configurations of the methyl groups reveal a 20-fold ground state degeneracy presiding in each molecule rendering the system to become highly unstable. From such, it is interpreted that T1 and T2 are temperatures at which the molecules successively lower their symmetry to remove the energy degeneracy which involve methyl group elongation and further out-of-plane tilting. This triggers the system to phase transition into the near-cubic phase which involves a shearing of the molecular planes and partial rotation of the methyl groups at T3 and T4. We interpret the low temperature near-cubic phase to be a manifestation of Jahn-Teller distortions based on energy degeneracies of the orbital motion of protons in each molecule and suggest that the metastable nature of the phase transition originates from the methyl groups requiring a larger amount of energy to order than to disorder. Our findings help explain why many unusual structural phase transitions occur at low temperatures in other molecular crystals possessing periodic motion of protons. {This manuscript is the unedited version of the Author's submitted work which was subsequently accepted (December 4 th , 2018) for publication in the Journal of Physical Chemistry C after peer review. To access the final edited and published version of this work, please visit [https://pubs.acs.org/doi/10.1021/acs.jpcc.8b09864]. Thank You.} 105 110 115 120 125

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Communication: Molecular gears

Cited by 10 publications

References 27 publications

Evolutionary algorithms and nuclear magnetic resonance of oriented molecules

Evolutionary algorithms and nuclear magnetic resonance of oriented molecules

Recent progress in NMR study of liquid-crystal assemblies

Magnetically Driven Structural Phase Transition in Hexamethylbenzene

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