Elastically Flexible Crystals have Disparate Mechanisms of Molecular Movement Induced by Strain and Heat

Brock, Aidan J.; Whittaker, Jacob J.; Powell, Jami; Pfrunder, Michael C.; Grosjean, Arnaud; Parsons, Simon; McMurtrie, John C.; Clegg, Jack K.

doi:10.1002/anie.201806431

Cited by 71 publications

(56 citation statements)

References 38 publications

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“…Notably, 1 is isomorphous to [Cu(acac) 2 ], which has recently been shown to form easily deformable crystals. [44][45][46] Any similar plasticity in crystals of 1 could be coupled to dramatic changes in both the optical and magnetic properties following the {Cr II -(acac) 2 2À } % {Cr III -(acac) 2 c 3À } valence tautomerization. The valence tautomers 2-4 exhibit extremely strong Cr IIIradical exchange interactions, as demonstrated by magnetization measurements and DFT calculations.…”

Section: àmentioning

confidence: 99%

Ligand field-actuated redox-activity of acetylacetonate

et al. 2020

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Section: àmentioning

confidence: 99%

Ligand field-actuated redox-activity of acetylacetonate

et al. 2020

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“…The ease and speed by which temperature-dependent X-ray diffraction data can be measured on modern laboratory ISSN 2052-5206 instruments, combined with accessible analysis tools such as the PASCal web server (Cliffe & Goodwin, 2012), make it straightforward to measure and assess thermal expansion, and there are indications that there is growing interest in reporting such data (e.g. Turner et al, 2018;Brock et al, 2018;Juneja et al, 2019;Ding et al, 2020;Upadhyay et al, 2021). In this context, a consistent survey of thermal expansion behaviour for the large set of molecular crystals in the Cambridge Structural Database (CSD; Groom et al, 2016) seems timely.…”

Section: Introductionmentioning

confidence: 99%

A survey of thermal expansion coefficients for organic molecular crystals in the Cambridge Structural Database

Bond¹

2021

Acta Crystallogr B Struct Sci Cryst Eng Mater

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Typical ranges of thermal expansion coefficients are established for organic molecular crystals in the Cambridge Structural Database. The CSD Python API is used to extract 6201 crystal structures determined close to room temperature and at least one lower temperature down to 90 K. The data set is dominated by structure families with only two temperature points and is subject to various sources of error, including incorrect temperature reporting and missing flags for variable-pressure studies. For structure families comprising four or more temperature points in the range 90–300 K, a linear relationship between unit-cell volume and temperature is shown to be a reasonable approximation. For a selected subset of 210 structures showing an optimal linear fit, the volumetric expansion coefficient at 298 K has mean 173 p.p.m. K−1 and standard deviation 47 p.p.m. K−1. The full set of 6201 structures shows a similar distribution, which is fitted by a normal distribution with mean 161 p.p.m. K−1 and standard deviation 51 p.p.m. K−1, with excess population in the tails mainly comprising unreliable entries. The distribution of principal expansion coefficients, extracted under the assumption of a linear relationship between length and temperature, shows a positive skew and can be approximated by two half normal distributions centred on 33 p.p.m. K−1 with standard deviations 40 p.p.m. K−1 (lower side) and 56 p.p.m. K−1 (upper side). The distribution for the full structure set is comparable to that of the test subset, and the overall frequency of biaxial and uniaxial negative thermal expansion is estimated to be < 5% and ∼30%, respectively. A measure of the expansion anisotropy shows a positively skewed distribution, similar to the principal expansion coefficients themselves, and ranges based on suggested half normal distributions are shown to highlight literature cases of exceptional thermal expansion.

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“…Typical examples include metal-organic frameworks that possess wine-rack structures, wherein large uniaxial PTE could occur in one direction with concomitant NTE in the perpendicular direction as a consequence of sideways contraction of the rhombic structure 1,2,15–18 . Unusual thermal expansion can also be induced by the collective significant reorientation of non-spherical molecules 4,6,19–21 . However, the significantly large molecular reorientation is usually restricted due to intermolecular interactions and steric effects in solid-state materials.…”

Section: Introductionmentioning

confidence: 99%

Giant anisotropic thermal expansion actuated by thermodynamically assisted reorientation of imidazoliums in a single crystal

et al. 2019

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Materials demonstrating unusual large positive and negative thermal expansion are fascinating for their potential applications as high-precision microscale actuators and thermal expansion compensators for normal solids. However, manipulating molecular motion to execute huge thermal expansion of materials remains a formidable challenge. Here, we report a single-crystal Cu(II) complex exhibiting giant thermal expansion actuated by collective reorientation of imidazoliums. The circular molecular cations, which are rotationally disordered at a high temperature and statically ordered at a low temperature, demonstrate significant reorientation in the molecular planes. Such atypical molecular motion, revealed by variable-temperature single crystal X-ray diffraction and solid-state NMR analyses, drives an exceptionally large positive thermal expansion and a negative thermal expansion in a perpendicular direction of the crystal. The consequent large shape change (~10%) of bulk material, with remarkable durability, suggests that this complex is a strong candidate as a microscale thermal actuating material.

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Elastically Flexible Crystals have Disparate Mechanisms of Molecular Movement Induced by Strain and Heat

Cited by 71 publications

References 38 publications

Ligand field-actuated redox-activity of acetylacetonate

Ligand field-actuated redox-activity of acetylacetonate

A survey of thermal expansion coefficients for organic molecular crystals in the Cambridge Structural Database

Giant anisotropic thermal expansion actuated by thermodynamically assisted reorientation of imidazoliums in a single crystal

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