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The physico-chemical processes supporting life’s purposeful movement remain essentially unknown. Self-propelling chiral droplets offer a minimalistic model of swimming cells and, in surfactant-rich water, droplets of chiral nematic liquid crystals follow the threads of a screw. We demonstrate that the geometry of their trajectory is determined by both the number of turns in, and the handedness of, their spiral organization. Using molecular motors as photo-invertible chiral dopants allows converting between right-handed and left-handed trajectories dynamically, and droplets subjected to such an inversion reorient in a direction that is also encoded by the number of spiral turns. This motile behavior stems from dynamic transmission of chirality, from the artificial molecular motors to the liquid crystal in confinement and eventually to the helical trajectory, in analogy with the chirality-operated motion and reorientation of swimming cells and unicellular organisms., Converting chemical energy into movement is essential to all forms of life, but the molecular processes are yet to be uncovered. Here the authors show a light-responsive reorientation behavior in liquid crystal droplets which stems from dynamic inversion of chirality from molecules to liquid crystals in confinement.

1,2-Bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene shows photochromism in n -hexane at room temperature. We have identified a new compound produced by the thermal decomposition in a mixture of cis - and trans -decahydronaphthalene above 100 °C in the absence of light.

Turn-on mode fluorescent diarylethenes such as 1,2-bis(2-alkyl-6-phenyl-1-benzothiophene-1,1-dioxide-3-yl)perfluorocyclopentene were applied to ultrahigh-sensitive fluorescence dosimeters. The dosimeters can detect absorbed dose as low as 50 mGy. The sensitivity is 102–103 times higher than that of conventional colour dosimeters.

Three 1,2-bis(2-alkyl-1-benzothiophene-3-yl)perhydrocyclopentenes with different alkyl chain lengths (methyl, ethyl, and propyl) at the reactive carbons were synthesized, and their photophysical properties were compared with those of 1,2-bis(2-alkyl-1-benzothiophene-3-yl)perfluorocyclopentenes. The structures of the perhydrocyclopentenes were analyzed by X-ray crystallography, and their cyclization/cycloreversion reaction and fluorescence quantum yields, and fluorescence lifetimes were measured by steady-state spectroscopy and the time-correlated single photon counting method, respectively. From these results, we found the following three differences between perhydrocyclopentenes and perfluorocyclopentenes. (1) For the closed-ring isomers, the absorption bands of the perhydrocyclopentenes (around 450 nm) shifted to a shorter wavelength than those of the perfluorocyclopentenes (around 530 nm) because of the acceptor nature of the perfluorocyclopentene moiety. (2) The cyclization/cycloreversion quantum yields of the perhydrocyclopentenes were slightly larger than those of the perfluorocyclopentenes in hexane. (3) Interestingly, the fluorescence of both the open- and closed-ring isomers was observed only for the perhydrocyclopentenes, and the lifetimes of the closed-ring isomers were estimated to be

Three types of diarylethenes having one phenol moiety as an aromatic unit were synthesized in order to control pH change upon irradiation with UV and visible light. Upon irradiation with 313 nm lig...

Photochromic benzo[b]silole derivatives, 1-(1,1-dimethyl-2-phenylbenzo[b]silol-3-yl)-2-(2-phenylbenzo[b]thien-3-yl)perfluorocyclopentene and 1-(1,1-dimethyl-2-phenylbenzo[b]silol-3-yl)-2-(2-phenyl-1-benzofuran-3-yl)perfluorocyclopentene, were synthesized and their photochromic performance was examined in solution.

We have synthesized three diarylethene derivatives — 1,2-bis(2-(4-n-alkylphenyl)benzofuran-3-yl)ethenes (1a–3a). We have observed the morphology changes of the melted diarylethenes after heating. The crystal of 2a melts at 102 °C. After heating at 130 °C, the liquid did not crystallize below 40 °C for more than 3 days because of the temperature above the eutectic point. When the liquid was irradiated with 365 nm light, the photoirradiated area crystallized, because of the generation of 2b. After the sample was irradiated with visible light, the crystals changed to a colorless liquid. Photoinduced crystallization was also observed for the 4-n-dodecyl derivative (3a).

Four diarylethene derivatives ( 3a – 6a ) bearing an oxazole ring have been prepared in an attempt to construct a system that shows photochromism upon UV irradiation in a crystalline phase. The crystals ( 3a , 5a , and 6a ) did not show photochromism in the crystalline phase. A pure single crystal of 1-(2-methyl-1-benzofuran-3-yl)-2-(5-methyl-2-phenyl-4-oxazolyl)perfluorocyclopentene ( 4a ) shows photochromism only in a single-crystalline phase. X-ray analysis proved that 4a packs in an anti-parallel orientation, which demonstrates photochromism in a single-crystalline phase.

Photochromic diarylethene regioisomers having benzothiophene and benzofuran rings were synthesized and their structures were confirmed by X-ray crystallography. The photochromic properties of these...

1,2-Bis(1-benzofuran-3-yl)perfluorocyclopentene derivatives having iodo, phenyl, 2,4-diphenylphenyl, nitro, and formyl substituents at the 6 position of the benzofuran ring were synthesized. The photoreactivities of these compounds were studied in terms of the measured quantum yields and the conversions in the photostationary state. The mono- and bis-2,4-diphenylphenyl derivatives showed photochromism in an amorphous phase.

Diarylethene derivatives having 1,2-bis(3-n-alkyl-1-benzothiophen-2-yl)perfluorocyclopentene have been synthesized to examine their photochromic properties in solution. All the derivatives underwent photochromism in hexane. The introduction of long-chain substituents to the 3-positions of a 1-benzothiophene unit leads to longer wavelengths of the absorption band of the closed-ring isomer. However, the cyclization quantum yields of these compounds showed no increase with alkyl chain length.

Light technology is based on generating, detecting and controlling the wavelength, polarization and direction of light. Emerging applications range from electronics and telecommunication to health, defence and security. In particular, data transmission and communication technologies are currently asking for increasingly complex and fast devices and therefore there is a growing interest in materials that can be used to transmit light and also to control the distribution of light in space and time. Here, we design chiral nematic microspheres whose shape enables them to reflect light of different wavelengths and handedness in all directions. Assembled in organized hexagonal superstructures, these microspheres of well-defined sizes communicate optically with high selectivity for the colour and chirality of light. Importantly, when the microspheres are doped with photo-responsive molecular switches, their chiroptical communication can be tuned, both gradually in wavelength and reversibly in polarization. Since the kinetics of the “on” and “off” switching can be adjusted by molecular engineering of the dopants and because the photonic cross-communication is selective with respect to the chirality of the incoming light, these photo-responsive microspheres show potential for chiroptical all-optical distributors and switches, in which wavelength, chirality and direction of the reflected light can be controlled independently and reversibly.

Topology is a universal concept that is encountered in daily life and is known to determine many static and dynamical properties of matter. Taming and controlling the topology of materials therefore constitutes a contemporary interdisciplinary challenge. Building on the controllable spatial properties of soft matter appears as a relevant strategy to address the challenge, in particular, because it may lead to paradigmatic model systems that allow checking theories experimentally. Here we report experimentally on a wealth of complex free-standing metastable topological architectures at the micron scale, in frustrated chiral nematic droplets. These results support recent works predicting the formation of free-standing knotted and linked disclination structures in confined chiral nematic fluids. We also demonstrate that various kinds of external fields (thermal, electrical and optical) can be used to achieve topological remote control. All this may foster the development of new devices based on topologically structured soft media., Controlling the topology of matter offers an alternative way to make functional materials, among which liquid crystals hold promise due to their spontaneously occurring defects. Here Orlova et al. demonstrate the formation and remote control of topological structures in frustrated cholesteric droplets.

Photochromic diarylethene derivatives having benzofuran heteroaryl groups, bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene and bis(2-butyl-1-benzofuran-3-yl)perfluorocyclopentene, were synthesized, and their photochromic performance was examined in hexane solution as well as in the single-crystalline phase. The compounds exhibited photochromic reactivity even in the single-crystalline phase.

Photochromic diarylethenes having benzofuran and benzothiophene rings have been synthesized and their photochromic performance in a single-crystalline phase has been examined. Although l,2-bis(2-methyl-1-benzothiophen-3-yl)perfluorocyclopentene (la) is photochemically inactive in the single-crystalline phase, diarylethene derivatives having a benzofuran ring (2a and 3a) undergo photochromism in the single-crystalline phase. 1-(1-Benzofuran-3-yl)-2-(1-benzothiophen-3-yl)hexafluorocyclopentene having ethyl, propyl, and butyl chains at the 2-position (4a-6a) were also synthesized. The derivative having propyl chains (5a) underwent photochromism in a single-crystalline phase. Upon UV irradiation, the crystal showed a brilliant red color in the single-crystalline phase.

Photochromism of bis(2-n-alkyl-1-benzothiophen-3-yl)perfluorocyclopentene derivatives has been studied in solution as well as in the single crystalline phase. Introduction of the long alkyl chains at 2-positions of bis(1-benzothiophen-3-yl)perfluorocyclopentene was found to increase the cyclization quantum yield and induce bathochromic shifts of the absorption spectra of the closed-ring isomers. The derivatives with ethyl, propyl, and butyl substituents at the 2-positions exhibit photochromism even in the single crystalline phase.

Diarylmaleimide derivatives having an indole ring, N-cyanomethyl-2-[2-methoxy-l-benzothiophen-3-yl]-3-[2-methyl-1-octadecylindol-3-yl]maleimide or N-cyanomethyl-2-[2-ethoxy-1-benzothiophen-3-yl]-3-[2-methyl-1-octadecylindol-3-yl]maleimide, were synthesized in an attempt to shift the photosensitive wavelength longer such that it becomes longer than 450 nm. The derivatives underwent the photocyclization reaction upon irradiation with 450-550 nm light in hexane solution and the photogenerated closed-ring isomers returned to the initial open-ring isomers upon irradiation with light longer than 600 nm.

Diarylethene derivatives having one or two chryso[b]thiophene ring(s) have been synthesized. In solution the derivatives underwent photochromism and the derivative with one chryso[b]thiophene ring exhibited photochromism even in the single crystalline phase. The color of the UV irradiated single crystal changed from blue to green by rotation the sample under polarized light.

1,2-Bis(5-n-alkyl-2-phenyloxazol-4-yl)perfluorocyclopentenes were synthesized and their photochromic performance was examined in hexane solution as well as in single-crystalline phase.

Photochromic chiral compounds having two diarylethene units were synthesized in an attempt to use them as dopants for photoresponsive liquid crystals. Stable photoswitching of the photochromic dopants induced large pitch changes of chiral nematic liquid crystals composed of K-15 and a small amount of the chiral dopants.

Substituent effect on the photochromic reactivity of bis(2-thienyl)perfluorocyclopentenes was examined. Introduction of phenyl groups having electron-donating substituents on the para -position of the phenyl ring to the 5-position of the thiophene rings shifted the absorption bands of the open-ring isomers to longer wavelengths and reduced the quantum yield of the cyclization reactions. The substitution with p -( N , N -diethylamino)phenyl groups prohibited the cyclization reaction. The absorption spectra of the closed-ring isomers were not influenced by the substitution.

A chiral cyclohexane having two photochromic diarylethene unit was synthesized in an attempt to use it as a dopant for a photoresponsive liquid crystal. A stable photoswitching between nematic and cholesteric phases could be induced by the addition of a small amount of the chiral cyclohexane to a nematic liquid crystal 4-cyano-4′-penthylbiphenyl (K-15).

A chiral cyclohexane containing two photochromic azobenzene units, (1R,2R)-N,N′-bis[4-(phenylazo)benzylidene]-1,2-cyclohexanediamine, was synthesized in an attempt to construct a molecule which shows a large optical rotation change due to photoirradiation. The CD spectrum dramatically changed depending on the configuration of the two azobenzene units. The specific rotations of (E,E)-, (E,Z)- and (Z,Z)-isomers were −1400°, −940°, and −670°, respectivly, while that of the monosubstituted chiral cyclohexane, (1R, 2R)-N-[(4-phenylazo)benzylidene]-N′-benzylidene-1,2-cyclohexanediamine ((E)-isomer), was only −470°. There was no difference in the photoisomerization rates of the azobenzene chromophores attached to chiral and nonchiral cyclohexanes.

The radiation sensitivity of photochromic 1,2-dithienylethenes was studied with the aim to develop a new reusable color dosimeter. Upon γ-irradiation, crystalline colorless 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene turned red, and the absorption intensity increased linearly with the absorbed dose. The red color was bleached by visible-light irradiation and the crystal could be reused. On the other hand, crystalline 1,2-bis(2-methyl-1-benzothiophen-3-yl)perfluorocyclopentene did not show any radiation-induced coloration. The radiation sensitivity in solution was also examined to understand the possible applications to solution and film color dosimeters. Although radiation-induced coloration of the above two compounds was observed in benzene, no color change was detected in hexane, 2-methyltetrahydrofuran and n-butyl chloride. Excitation energy migration and transfer mechanism is considered to play a role in the coloration process in benzene.

Photochromic indene derivatives, 1-(2-methyl-1-inden-3-yl)-2-(2-methyl-1-benzothien-3-yl)perfluorocyclopentene and 1-(2-methyl-1-inden-3-yl)-2-(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene, were synthesized and their photochromic performance was examined.

Diarylethene derivatives, which have an optically active l- or d-menthyl group at the 2-position of benzo[b]thiophene ring, were synthesized. Irradiation with 450 nm light in solution led to the formation of diastereomer pairs of the closed-ring forms. The product ratio of the diastereomers was dependent on solvent polarity and temperature. In slightly polar (or polarizable) solvents, such as THF and toluene, an asymmetric photocyclization was observed. At −40 °C in toluene, a diastereomer excess as large as 86.6% was observed. The mechanism of the asymmetric photocyclization is discussed.

Non-symmetric diarylethenes that have a 1-benzothiophene ring on one end and a 2-thienyl or 3-thienyl group on the other end of the double bond of maleimide were synthesized in order to study the effects of the substitution position of the thiophene ring on the absorption bands and the reactivities. The open-and closed-ring forms of N-cyanomethyl-2-(2,4-dimethyl-5-phenyl-3-thienyl)-3-(2-methoxy-1-benzothiophen-3-yl)maleimide showed absorption bands at 420 and 563 nm in hexane, respectively. When 3-thienyl was changed to 2-thienyl, the absorption bands of N-cyanomethyl-2-(3,4-dimethyl-5-phenyl-2-thienyl)-3-(2-methoxy-1-benzothiophen-3-yl)maleimide shifted to 448 nm (the open-ring form) and 487 nm (the closed-ring form), respectively. The cyclization and ring-opening quantum yields were also dependent on the substitution position. The cyclization yield decreased from 0.30 to 0.03 by changing the position from 3- to 2-thienyl, while the ring-opening yield increased from 0.03 to 0.13. No absorption spectral c...

Substituent effect on the photochromic reactivity of bis(2-thienyl)perfluorocyclopentenes was examined. Introduction of phenyl groups having electron-donating substituents on the para -position of the phenyl ring to the 5-position of the thiophene rings shifted the absorption bands of the open-ring isomers to longer wavelengths and reduced the quantum yield of the cyclization reactions. The substitution with p -( N , N -diethylamino)phenyl groups prohibited the cyclization reaction. The absorption spectra of the closed-ring isomers were not influenced by the substitution.

A novel type diarylethene derivative having a chryso[b]thiophenes ring has been synthesized and its photochromic reaction has been studied in ethyl acetate.

A chiral cyclohexane containing two photochromic diarylethene units was synthesized in an attempt to use it as a dopant for a photoresponsive liquid crystal. A stable photoswitching between nematic and cholesteric phases could be induced by the addition of a small amount of the chiral cyclohexane to a nematic liquid crystal 4-cyano-4‘-penthylbiphenyl (K-15).

[reaction: see text] Photochromic diarylethene derivatives having benzofuran heteroaryl groups, bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene and bis(2-butyl-1-benzofuran-3-yl)perfluorocyclopentene, were synthesized, and their photochromic performance was examined in hexane solution as well as in the single-crystalline phase. The compounds exhibited photochromic reactivity even in the single-crystalline phase.

Photochromic diarylethene dimer derivatives with large two-photon absorption (TPA) cross-sections have been designed and synthesized. The derivatives have a D-pi-D structure in which indole rings are used as donor units (D) and 1,4-bis(ethynyl)benzene or 1,4-bis(ethenyl)benzene as a pi-conjugated chain unit (pi). Compound 5 a, which has oxazole rings as one of the aryl groups, showed a TPA cross-section of 23 GM at 820 nm and exhibited efficient two-photon photochromic reactivity.

Photochromic 2-aryl-3-(1-propenyl)maleic anhydride derivatives were synthesized by one pot synthesis and their photochromic performance was examined in solution.

Diarylmaleimide derivatives having methoxy, phenyl, or cyano group as a nitrogen substituent were synthesized in an attempt to prepare photochromic compounds which exhibit photochromic reactivity even in polar solvents. Although the derivatives having methoxy or phenyl group did not undergo photochromism in polar solvents, the derivative having a cyano group showed photochromism even in polar solvents.

Two kinds of chiral diarylethene derivatives were synthesized and used as dopants for photoresponsive liquid crystals. Both derivatives underwent thermally irreversible and fatigue resistant photochromic reactions and exhibited reversible circular diochroism (CD) spectral changes. Large photostimulated pitch chances of chiral nematic K-15 liquid crystals were observed by the addition of the derivatives as dopants. The relation between the optical rotation and the twisting power force was discussed.

An aqueous mixture of cetyltrimethylammonium bromide (CTAB) and 2,3-dihydroxynaphthalene (2,3-DHN) gives a viscous solution of rodlike nanoaggregates as confirmed by transmission electron microscop...

Photochromic 2-aryl-3-(1-propenyl)maleic anhydride derivatives were synthesized by one pot synthesis and their photochromic performance was examined in solution.

A photochromic compound having three diarylethene units was synthesized and its photochromic performance was examined in hexane solution as well as in a bulk amorphous phase. The compound formed a ...

A novel photochromic molecule having a bis(2,3'-benzothienyl) unit has been synthesized. The derivative underwent a thermally irreversible photochromic reaction upon alternate irradiation with UV and visible light.

Dithienylethenes having a pyridinium cation at one and both thiophene rings were synthesized. The derivatives with two pyridinium cation showed the cyclization quantum yield as high as 0.71, which is much larger than the values of the monocation derivative and the neutral form. This can be explained by the conformation of the open-ring isomer of the diarylethenes.

A novel type diarylethene derivative having a chryso[b]thiophenes ring has been synthesized and its photochromic reaction has been studied in ethyl acetate.

A chiral cyclohexane having two diarylethene chromophores was synthesized in an attempt to construct a molecule which shows a large optical rotation change by photoirradiation. Circular dichroism (CD) and optical rotation were found to change dramatically upon photoirradiation.

Photochromic diarylethenes having furan units (1 and 3) were synthesized and their photochromic performances were compared with those having thiophene units. The cyclization quantum yields of both derivatives in hexane are similar. In contrast, the cycloreversion quantum yield of the derivative having furan units (1) is much larger than that having thiophene units (2) in hexane. The difference is attributed to the conformation of the closed-ring isomers. Although 2a and 4a do not show any fluorescence, 1a and 3a exhibit fluorescence. Photochromism in the single crystalline phase was also observed for 1 and 3. Upon irradiation with 313 nm light, the colorless crystals 1 and 3 changed to violet and yellow, respectively.