Themed collection Mechanically responsive crystalline materials

Guest editors Changquan Calvin Sun and C. Malla Reddy introduce the CrystEngComm themed issue on ‘Mechanically responsive crystalline materials’.

The DFT-predicted mechanical properties of crystalline materials are crucial knowledge for their screening, design, and exploitation.

Dynamic macroscopic behaviour of single crystals of coordination polymers when subjected to light, heat, and mechanical force.

A newly developed methodology allows for the determination of the mechanisms of deformation in flexible crystals with atomic precision. With broader applications, mapping experiments have wide reaching potential within the field of materials science.

Flexible molecular crystals have attracted much attention to unique optoelectronic applications and stimuli-responsive chemistry, resulting in various functional molecular crystals for controlling photons, phonons, electrons, and magnons.

Crystal adaptronics has undergone tremendous developments that have been utilized to rationalize dynamics in crystals. This highlight discusses about the role of intermolecular interactions in rationalizing mechanical responses in crystals.

A novel crystal of PTX-2CF₃ exhibits room temperature phosphorescence and mechanical flexibility. This flexible crystal efficiently transduces optical emission both in the straight and bent geometries.

The two isomeric zeolite-like metal–organic frameworks based on tetrahedral TPO³⁻ ligands and tetrahedrally connected Cd²⁺ ions were prepared. One of the compounds shows mechanic-responsive luminescence after the crystals were ground for different time.

Thermal expansion study has been used to understand the mechanism of elastic bending in 9,10-anthraquinone. Expansion along the bending axis due to bending is expected to resemble the thermal expansion along the same direction.

Mechanical deformation-induced physical property changes of elastically flexible molecular crystals were successfully investigated by spatially resolved μ-photoluminescence (PL) spectroscopy for the PL analysis at both the outer and inner sides.

Orange (Cry-1O) and red (Cry-1R) emissive crystals were obtained based on a green emissive molecule 1. The light transducing capability of Cry-1R in both the straight and bent states can be applied as an active optical waveguiding medium.

A combined experimental/computational analysis of photomechanical anthracene derivatives reveals their kinetic behavior is not simply related to the monomer-photodimer energetics.

The ability to selectively tune the optical and the mechanical properties of organic molecular crystals offers a promising approach towards developing flexible optical devices.

Unique mechanical properties in molecular solids arise from a specific combination of structure and interaction anisotropy. Powder Brillouin light scattering offers new insight into the latter contribution to test current models for mechanical design.

A rod-shaped self-assembling diacetylene-linked bis-benzothiadiazole derivative presents a high contrast luminescence phase transformation upon shearing which is reversed upon heating.

A pseudorotaxane with different or mixed counter anions undergoes thermal phase transition, which is related to the interaction between the counter anion and macrocyclic component.

Atomic force microscopy was used to determine roughness, elastic modulus and work function after thermally-induced and solvent-induced dehydration. These properties correlated with electric charging to provide insight into behaviour of bulk powders.

Pure organic multi-color luminescent materials were finely tuned from blue through green to red using a supramolecular complex strategy, exhibiting force- and solvent-sensitive luminescence switching in the stimuli-responsive field.

The three polymorphic crystals of a donor–acceptor dye exhibited different luminescence colors, which changed in response to mechanical grinding.

A series of polyhalogenated platinum(II)–bipyridine complexes showed solvent-of-crystallisation-dependent elastic flexibility and luminescence.

Mechanofluorochromic crystals based on tetraphenylethylene and boronates reversibly change their emission upon grinding, setting the path to develop bistable switches in the future.

A diketopyrrolopyrrole dye was found to exhibit a three-step polymorphic transition by heating with thermosalient effects.

Photoinduced topographical changes, bending, and photosalient effect due to the dimerization reaction were observed on a single crystal of 7-methoxycoumarin, upon deep UV (254 nm) light irradiation.

A novel alkyltolane-terminated cyanostilbene is synthesized. The photoluminescence colour changed depending on the precipitation method, with either a red shift or blue shift in the photoluminescence spectra observed upon mechanical grinding.

We report here a new green fluorescent organic crystal of an amide functionalized acrylonitrile derivative (E-ArF₂) that displays various types of macroscopic response when illuminated with UV light (390 nm).

A unique mechanical property of superelasticity is observed not only in so-called shape-memory alloys but also in molecular crystals.

The higher the number of fluorine atoms, the higher the topological photo-induced [2 + 2] cycloaddition reactivity of chalcones.

The bending deflection and blocking force of photo-bending crystals of different sizes were experimentally measured at various light intensities, and then modeled by the machine learning-based regression.

Two epimeric series of esters exhibit distinct mechanical behaviour: brittle crystals for one series and ductile crystals for the other series.

Nanoindentation measurements in single crystals of carbamazepine form III show that the (020) face is stiffer and harder than the (002) and (101) faces. AFM imaging and molecular simulations reveal that the (020) plane is the most likely slip plane.

The unusual photomechanical behaviour of a “twin crystal” consisting of a diarylethene derivative was investigated.