Solid triphenylmethanol: A molecular material that undergoes multiple internal reorientational processes on different timescales

Kitchin, Simon J.; Xu, Ming; Serrano-González, Heliodoro; Coates, Laura J.; Ahmed, Sajjad; Glidewell, Christopher; Harris, Kenneth David Maclean

doi:10.1016/j.jssc.2006.01.047

Cited by 9 publications

(5 citation statements)

References 20 publications

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“…To estimate the exchange rate as a function of temperature, the spectra were simulated 15 with a two-fold flipping model (180°rotation) and an adjustable frequency. A reduction of the quadrupolar coupling constant from 180 to 160 kHz from the static spectra to the intermediate exchange is consistent with fast libration along the 1,4-axis, 16 indicating population of higher quantum states of torsional modes previously calculated at 43 and 87 cm -1 . 11 Arrhenius analysis of the exchange rate data resulted in E a ) 11.3 ( 2.0 kcal/mol and a pre-exponential factor A ) 1.6 × 10 12 s -1 (Figure 3).…”

supporting

confidence: 86%

Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment

et al. 2008

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Metal−organic frameworks (MOFs) have been the focus of much interest within the context of hydrogen storage and other materials applications. With static metal clusters linked by axially substituted organic spacers capable of experiencing internal rotations, MOFs are one of the most promising amphidynamic materials to investigate and exploit the dynamics of crystalline solids. In this communication we report an experimental study of the rotational dynamics of the 1,4-phenylenedicarboxylate bridge of MOF-5, which has no steric contacts that might contribute to the rotational barrier. Highly reproducible 1H T1 relaxation, high-resolution 13C CPMAS, and variable temperature quadrupolar echo 2H NMR data were obtained from high quality samples that were sealed at reduced pressure (ca. 3 mTorr). 2H NMR line shape simulation revealed an activation barrier for rotation of 11.3 ± 2.0 kcal/mol, which is lower than the 14−16 kcal/mol values reported in theoretical studies of truncated models. While our results suggest that the models used for MOF-5 are insufficient to account for the properties of the extended crystal lattice, they also suggest that the amphidynamic materials with static and dynamic components may reach the friction-free rotational motion characteristic of gas dynamics.

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confidence: 86%

Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment

et al. 2008

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“…In addition to −N + H 3 and −CH 3 groups, aryl rings can also undergo large amplitude motions in the solid state (particularly phenyl groups and p , p ′-disubstituted derivatives of benzene), as demonstrated from previous studies. − In most cases, aryl rings undergo a two-site 180° flip motion about an axis passing through two carbon atoms in para positions with respect to each other, although continuous rotation of aryl rings has also been observed, leading to considerable averaging of 2 H NMR spectra. , Interestingly, Frey et al reported that the dynamic properties of the phenyl ring in phenylalanine differ significantly for samples crystallized from water and from water/ethanol (presumably because different polymorphic forms are produced in each case). In the present work, the natural-abundance 2 H MAS NMR spectrum of benzyl triethylchloride (Figure S7, Supporting Information) contains signals assigned to deuterons in the methyl groups (0.9–1.5 ppm) and phenyl group (8.3 ppm).…”

Section: Resultsmentioning

confidence: 83%

Natural-Abundance Solid-State ²H NMR Spectroscopy at High Magnetic Field

et al. 2011

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High-resolution solid-state (2)H NMR spectroscopy provides a method for measuring (1)H NMR chemical shifts in solids and is advantageous over the direct measurement of high-resolution solid-state (1)H NMR spectra, as it requires only the application of routine magic angle sample spinning (MAS) and routine (1)H decoupling methods, in contrast to the requirement for complex pulse sequences for homonuclear (1)H decoupling and ultrafast MAS in the case of high-resolution solid-state (1)H NMR. However, a significant obstacle to the routine application of high-resolution solid-state (2)H NMR is the very low natural abundance of (2)H, with the consequent problem of inherently low sensitivity. Here, we explore the feasibility of measuring (2)H MAS NMR spectra of various solids with natural isotopic abundances at high magnetic field (850 MHz), focusing on samples of amino acids, peptides, collagen, and various organic solids. The results show that high-resolution solid-state (2)H NMR can be used successfully to measure isotropic (1)H chemical shifts in favorable cases, particularly for mobile functional groups, such as methyl and -N(+)H(3) groups, and in some cases phenyl groups. Furthermore, we demonstrate that routine (2)H MAS NMR measurements can be exploited for assessing the relative dynamics of different functional groups in a molecule and for assessing whole-molecule motions in the solid state. The magnitude and field-dependence of second-order shifts due to the (2)H quadrupole interaction are also investigated, on the basis of analysis of simulated and experimental (1)H and (2)H MAS NMR spectra of fully deuterated and selectively deuterated samples of the α polymorph of glycine at two different magnetic field strengths.

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“…The initial triple Grignard reaction from bromobenzene-d 5 (16) and diethyl carbonate offered a convenient pathway to triphenylmethanol-d 15 (17), and represented an alternative to a published method. 23 Treatment of 17 with tetrafluoroboric acid in propionic anhydride provided the carbenium ion 15 (Scheme 5). 22…”

Section: Preparation Of Substratesmentioning

confidence: 99%

“…Addition of b-ionone (8, 30.1 g, 0.156 mol) gave after work-up 33.1 g crude product, 96% yield. d H (400 MHz, CDCl 3 ) 0.99 (s, 6H), 1.43 (s, 3H), 1.45 (m, 2H), 1.61 (m, 2H), 1.67 (d, 3H, J = 0.9 Hz), 1.98 (m, 2H), 5.09 (dd, 1H, J = 1.2 Hz, J = 10.6 Hz), 5.28 (dd, 1H, J = 1.2 Hz, J = 17.3 Hz), 5.55 (d, 1H, 16.2 Hz), 6.02 (dd, 1H, J = 10.6 Hz, J = 17.3 Hz), 6.09 (m, 1H); m/z (EI) 221 (5.5%, M + 1), 220 (M + , 12.6), 205 (43), 202 (23), 193 (32), 189 (31), 187 (35), 177 (100), 175 (34), 161 (39), 159 (32), 149 (32), 147 (41), 145 (29), 137 (67), 121 (75).…”

Section: Vinyl-b-ionol (9)mentioning

confidence: 99%

Longer polyenyl cations in relation to soliton theory

2007

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The carotene-like polyenes decapreno-beta-carotene (C50), C54-beta-carotene (C54, first synthesis) and dodecapreno-beta-carotene (C60) with 15, 17 and 19 conjugated double bonds, respectively, were synthesized by double Wittig reactions. Introduction of a leaving group in allylic position failed, and cations were obtained by hydride elimination effected by i) triphenylcarbenium tetrafluoroborate-d15, prepared by a new method, or ii) treatment with trifluoroacetic acid-d. Deuterated reagents were employed for product analysis by 1H NMR. Parallel experiments were performed with beta,beta-carotene (C40). NIR spectra at room temperature and at -15 degrees C were employed for characterisation and stability studies of the cationic products. In CH2Cl2lambdamax in the 900-1350 nm region was recorded. NMR data for the cationic product of beta,beta-carotene obtained by the two new preparation methods were consistent with the two monocations previously characterised. The cationic products of the longer polyenes provided downfield-shifted, broadened signals, compatible with C50-monocation, mixed C54-mono- and dication and C60-dication. Combined NIR and NMR data suggest that the extent of charge delocalisation is limited by the maximum soliton width for cations obtained from linear polyenes with more than ca. 20 sp2-hybridized carbon atoms.

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Solid triphenylmethanol: A molecular material that undergoes multiple internal reorientational processes on different timescales

Cited by 9 publications

References 20 publications

Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment

Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment

Natural-Abundance Solid-State ²H NMR Spectroscopy at High Magnetic Field

Longer polyenyl cations in relation to soliton theory

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Solid triphenylmethanol: A molecular material that undergoes multiple internal reorientational processes on different timescales

Cited by 9 publications

References 20 publications

Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment

Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment

Natural-Abundance Solid-State 2H NMR Spectroscopy at High Magnetic Field

Longer polyenyl cations in relation to soliton theory

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Natural-Abundance Solid-State ²H NMR Spectroscopy at High Magnetic Field