The mechanism of bending in a plastically flexible crystal

Abstract

The mechanism of plastic deformation in crystals of a trifluoromethylated benzamide derivative has been determined with micro-focused X-ray diffraction. Fuorine–fluorine interactions are propose to mediated the observed mechanical behaviour.

Bending for Better: Flexible Organic Single Crystals with Controllable Curvature and Curvature‐Related Conductivity for Customized Electronic Devices

“…So far, for the bending crystal systems without mechanically interlocked architectures, as the coronene crystals in this work, [5d, 9b] structural changes of the bending region have been considered as both the lattice stretching in the outer arcs and the lattice compression in the inner arcs, accompanied by the consistent rotation of the molecules at the same arcs, which has been rationalized both theoretically and experimentally based on the crystallographic data in different arcs (Figure S22) [1f, 8j, 9c, 14, 31] . However, with a perspective from crystallography, the position of atoms in crystal obtained by the diffraction method is actually a cumulative value of the three‐dimensional linear periodic translational symmetric lattices, thus the subtle orientation difference between the adjacent two molecules in one single crystal is undetectable using existing technologies (even the synchrotron radiation technique) [37] .…”

“…Coronene is a rigid molecule and able to form one‐dimensional crystals with mechanical flexibility and controllable size by solution self‐assembly, which is reliable and easy‐to‐implement (Figure 1 a–g) [13b] . Structurally, strong face‐to‐face cofacial parallel stacked π–π interactions along the growth direction [010] (Figure 1 d,e,k), and weak edge‐to‐face T‐shape π‐π interactions along the [001] direction coexist, bringing only very weak dispersive interactions along the [10 ] direction (Figure 1 d,e,l, Figure S20,S21 and Table S3 for energy frameworks analysis), [6b, 14] which represents a remarkably bendable nature of the (10 ) plane, [1f, 8j, 9c, 15] consistent with the experimental facts that the crystals show elasticity when applying force at (10 ) plane and show brittleness when applying force at (001) plane (Figure 1 b,c,f,g, Movie S3, Figure S3,S17). However, the inherent herringbone packing motif without effective two‐dimensional π‐π overlap determines limited charge transport, [13a, 16] resulting in a conductivity less than 10 −12 S cm −1 [17] .…”

Mechanically compliant single crystals of a stable organic radical

“…This mechanism is consistent with those established for other plastically bendable crystals. 7,46,47 The crystals of 1b were found to be notably so when touched with a hard object, and this soness may play a role in the observed plasticity. The mechanical properties of a freshly sublimed crystal on its (101)/( 101) faces were quantied using a tensile tester equipped with a three-point bending apparatus (Fig.…”

“…It has been observed previously with halogen bonds or interactions in hexachlorobenzene, 30 hexabromobenzene, 5 and N -(4-ethynylphenyl)-3-fluoro-4-(trifluoromethyl)benzamide. 46 To our knowledge, 1 is the first example of a bendable crystal whose molecules interact via F–π or S–N interactions. These results indicate that even though similar motifs such as slip planes are commonly utilized to generate dislocations during bending, the interactions that define those slip planes can be varied.…”

A 47-year-old misunderstanding: Indomethacin Polymorph δ revealed to be two plastically bendable crystal forms by 3D electron diffraction

“…This slippage mechanism is the most common mechanism of plastic bending for molecular crystals. [49][50][51][52][53][54] No slip planes can be observed along the b-axis for melt δ-IDM nor parallel to the (100) plane for solution δ-IDM. This explains the one-dimensional plastic flexibility of the two polymorphs well.…”