Tomohiro Seki

Mechanoinduced phase transitions of emissive organic crystalline materials have received much attention. Although a variety of such luminescent mechanochromic compounds have been reported, it is challenging to develop mechanochromic compounds with crystal-to-crystal phase transitions in which precise structural information about molecular arrangements can be obtained. Here, we report a screening approach to explore mechanochromic compounds exhibiting a crystal-to-crystal phase transition. We pre

Green and blue polymorphs: A single-crystal-to-single-crystal (SCSC) phase transition of phenyl(3,5-dimethylphenyl isocyanide)gold(I) was triggered by mechanical picking or solid seeding and propagated spontaneously with a domino-like mechanism. As a result, one phase with intense green emission was transformed to another phase with weaker blue emission.

Upon mechanical stimulation, 9-anthryl gold(I) isocyanide complex 3 exhibited a bathochromic shift of its emission color from the visible to the infrared (IR) region, which is unprecedented in its magnitude. Prior to exposure to the mechanical stimulus, the polymorphs 3α and 3β exhibit emission wavelength maxima (λ_em,max) at 448 and 710 nm, respectively. Upon grinding, the λ_em,max of 3α_ground and 3β_ground are bathochromically shifted to 900 nm, i.e., Δ

We report the first photoinduced single-crystal-to-single-crystal (SCSC) phase transition of a gold complex that involves the shortening of intermolecular aurophilic bonds. This is also the first solid state photochromism of a gold complex. Upon UV irradiation, the blue-emitting crystals of the gold(i) isocyanide complex <b>1</b> (<b>1B</b>) transform into the weakly yellow-emitting polymorph <b>1Y</b>. X-ray diffraction analyses reveal that this phase transition proceeds in an SCSC manner. Afte

In this study, we report the interconvertible tetracolored solid state photoluminescence of gold(i) isocyanide complex <b>2</b> upon various external stimuli through solid state structural changes. Soaking complex <b>2</b> in acetone yields blue emission as a result of the formation of <b>2B</b>. The subsequent removal of acetone yields <b>2G</b> through a crystal-to-crystal phase transition, which exhibits green emission. This green-emitting solid <b>2G</b> exhibits stepwise emission color chan

The salient effect, which refers to a jumping phenomenon of organic and organometallic molecular crystals typically triggered by phase transitions in response to external stimuli, has been investigated intensively in the last five years. A challenging topic in this research area is the question of how to characterize the release of microscopic strain accumulated during phase transitions, which generates macroscopic mechanical motion. Herein, we describe the thermosalient effect of the triphenyle

Structural changes to molecular crystals upon mechanical stimulation have attracted attention for sensing, recording, and microactuation. Comprehensive structure information is required to understand relationships between the mechanical force applied, the crystal structure, and the bulk property changes in order to develop general design concepts for mechanoresponsive compounds. Unfortunately, mechanical stimulation of organic crystals typically deteriorates their integrity, preventing detailed

Ferroelasticity has been reported for several types of molecular crystals, which show mechanical-stress-induced shape change under twinning and/or spontaneous formation of strain. Aiming to create materials that exhibit both ferroelasticity and light-emission characteristics, we discovered the first examples of ferroelastic luminescent organometallic crystals. Crystals of arylgold(I)(N-heterocyclic carbene)(NHC) complexes bend upon exposure to anisotropic mechanical stress. X-ray diffraction ana

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.

Melamine-linked perylene bisimide dyes (MPBIs) bearing an ethylene or trimethylene group as linker moieties were synthesized, and their self-aggregation and coaggregation with cyanurates through complementary triple hydrogen bonds have been investigated. UV/vis studies revealed that both the MPBIs self-assemble in nonpolar organic solvent through pi-pi stacking interaction between perylene cores, giving self-aggregates with nearly identical thermal stabilities. Upon addition of 1 equiv of cyanur

Discotic supramolecular complexes bearing six perylene bisimide (PBI) chromophores were prepared by mixing monotopically triple-hydrogen-bonding melamines equipped with two PBI chromophores and two 3,7-dimethyloctyl chiral handles with tritopically triple-hydrogen-bonding cyanuric acid (CA). UV/Vis and fluorescence titration experiments demonstrated that the discotic complexes were formed in methylcyclohexane by the 3:1 complexation between the melamines and CA. TEM and AFM studies revealed that

Abstract Perylene bisimide (PBI) dyes are among the most extensively studied functional π‐building blocks and have outstanding optical and electronic properties. Most PBI assemblies that have been reported so far are based on one‐dimensional stacks formed mainly by directional π–π interactions between quadrupolar π‐systems of PBIs. More complex and elaborate supramolecular assemblies of PBIs can be constructed by using highly directional and specific intermolecular glues, such as complementary m

Mechano-induced phase transitions in organic crystalline materials, which can alter their properties, have received much attention. However, most mechano-responsive molecular crystals exhibit crystal-to-amorphous phase transitions, and the intermolecular interaction patterns in the daughter phase are difficult to characterize. We have investigated phenyl(phenylisocyanide)gold(I) (1) and phenyl(3,5-dimethylphenylisocyanide)gold(I) (2) complexes, which exhibit a mechano-triggered single-crystal-to

Luminescent mechanochromism of a chiral gold(i) complex is investigated. The racemic and homochiral forms of the gold(i) complex possess distinct crystal packing arrangements with different emission colors. Upon mechanical stimulation, both crystals transform into amorphous powders that exhibit similar emission colors.

The mechanochromic compound 1 forms green-emitting crystals (1g) and blue-emitting crystals (1b) that exhibit two intriguing responses to mechanical stimulation. Upon mechanical stimulation, the emission color of 1g does not change but its crystalline structure does. Conversely, 1b shows a clear emission shift, but it retains its molecular arrangement upon grinding.