Yoshimitsu Sagara

The possibility to change the molecular assembled structures of organic and organometallic materials through mechanical stimulation is emerging as a general and powerful concept for the design of functional materials. In particular, the photophysical properties such as photoluminescence color, quantum yield, and emission lifetime of organic and organometallic fluorophores can significantly depend on the molecular packing, enabling the development of molecular materials with mechanoresponsive lum

A novel design principle for materials showing piezochromic luminescence is proposed. Amide-substituted tetraphenylpyrene C6TPPy, composed of a planar fluorescent core and multiple hydrogen-binding sites, displays a remarkable change and restoration of its luminescence color by pressing with a spatula and heating, respectively.

Shear brilliance: The photoluminescent color of a pyrene-based liquid crystal changes from yellow to blue-green upon mechanical shearing due to a phase transition from a micellar cubic to a columnar phase (see picture).

The integration of mechanophores, motifs that transduce mechanical forces into chemical reactions, allows creating materials with stress-dependent properties. Typical mechanophores are activated by cleaving weak covalent bonds, but these reactions can also be triggered by other stimuli, and this renders the behavior unspecific. Here we show that this problem can be overcome by extending the molecular-shuttle function of rotaxanes to mechanical activation. A mechanically interlocked mechanophore

A glowing image: The photoluminescent colors reddish-orange, yellow, and green, are generated from a single liquid-crystalline mixture containing one luminophore (see picture). The colors are easily distinguished by the naked eye and can be reversibly written and erased. Moreover, these luminescent colors can be switched by mechanical and thermal stimuli. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-e

Bunte Bilder: Rotorangefarbene, gelbe und grüne Photolumineszenz wird von einer einzigen flüssigkristallinen Mischung erzeugt, die einen Luminophor enthält (siehe Bild). Die mit bloßem Auge unterscheidbaren Farben können reversibel gemalt und wieder gelöscht werden. Überdies lassen sich die Lumineszenzfarben durch mechanische und thermische Reize steuern. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-e

Abstract Here, a photoluminescent liquid crystal that exhibits a change of emission color on the metastable–stable phase transition induced by external stimuli is prepared. A 2,6‐diethynylanthracene derivative with amide groups and dendritic side chains exhibits a columnar phase on slow cooling from the isotropic phase and shows blue emission in this columnar phase. In contrast, a cubic phase is obtained by rapid cooling from the isotropic phase. In the cubic phase, the 2,6‐diethynylanthracene c

Three mechanoresponsive polyurethane elastomers whose blue, green, and orange photoluminescence can be reversibly turned on by mechanical force were prepared and combined to create a blend that exhibits deformation-induced white photoluminescence. The three polyurethanes contain rotaxane-based supramolecular mechanoluminophores based on π-extended pyrene, anthracene, or 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4<i>H</i>-pyran (DCM) luminophores, respectively, and 1,4,5,8-naphthale

A new approach to cyclophane-based supramolecular mechanophores is presented. We report a mechanically responsive cyclic motif that contains two fluorescent 1,6-bis(phenylethynyl)pyrene moieties that are capable of forming intramolecular excimers. The emission spectra of dilute solutions of this cyclophane and a polyurethane elastomer into which a small amount of the mechanophore (0.08 wt %) had been covalently integrated are dominated by excimer emission. Films of the cyclophane-containing poly

Mechanochromic mechanophores permit the design of polymers that indicate mechanical events through optical signals. Here we report rotaxane-based supramolecular mechanophores that display both reversible and irreversible fluorescence changes. These responses are triggered by different forces and are achieved by exploiting the molecular shuttling function and force-induced dethreading of rotaxanes. The new rotaxane mechanophores are composed of a ring featuring a luminophore, which is threaded on

Mechanoresponsive luminescent (MRL) compounds change their emission color upon mechanical treatment. Hundreds of MRL compounds have been studied, but their mechanically triggered response at elevated temperature has remained virtually unexplored. Here, we demonstrate that the temperature can have a significant influence on the mechanically induced response of MRL compounds. The photoluminescence of a new cyano-substituted oligo(p-phenylenevinylene) derivative was shown to exhibit a significant r

Formbare Farben: Die Farbe der Photolumineszenz von Flüssigkristallen auf Pyrenbasis wechselt auf eine mechanische Scherung hin von Gelb nach Blaugrün. Die Ursache hierfür ist der Übergang von einer micellar-kubischen in eine columnare Phase (siehe Bild). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2008/z800164_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporti

Abstract Switching of the luminescence properties of molecular materials in response to mechanical stimulation is of fundamental interest and also has a range of potential applications. Herein, a water‐soluble mechanochromic luminescent pyrene derivative having two hydrophilic dendrons is reported. This pyrene derivative is the first example of a mechanochromic luminescent organic compound that responds to relative humidity. Mechanical stimulation (grinding) of this pyrene derivative in the soli

Covalent attachment of mechanoresponsive luminescent organic or organometallic compounds to other materials is a promising approach to develop a wide variety of mechanoresponsive luminescent materials. Here, we report covalently linkable mechanoresponsive micelles that change their photoluminescence from yellow to green in response to mechanical stimulation under aqueous conditions. These micelles are composed of a dumbbell-shaped amphiphilic pyrene derivative having amine groups at the peripher