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Photoswitching molecules that reversibly switch upon visible-light irradiation are some of the most attractive targets for biological and imaging applications. In this study, we found a diarylethene (DAE) derivative having a covalently attached perylenebisimide (PBI) unit (DAE-PBI dyad) underwent an unexpected cyclization reaction upon irradiation with green (500-550 nm) light, where the DAE unit has no absorbance. The photoreactivity was enhanced in solvents containing heavy atoms and in the presence of oxygen. As inferred from the solvent dependence and the calculated excited-state energies of DAE and PBI units, it was suggested that the probable mechanism for this unique visible-light-induced cyclization reaction is multiplicity conversion based on intramolecular energy transfer from the excited singlet state of the PBI unit to the triplet state of DAE units (i.e., DAE

Amphiphilic diarylethene with tri(ethylene glycol) chains as a hydrophilic moiety and octylcarbamoyl chain as a hydrophobic moiety formed a supramolecular assembly by hydrophobic interactions in wa...

The origin of aggregation-induced enhanced emission (AIEE) is investigated considering cyano-substituted 1,2-bis(pyridylphenyl)ethene (CNPPE) as an example. On the basis of ONIOM calculations using time-dependent density functional theory (TD-DFT), we found that pseudo-degeneracy of excimers formed in solid phase plays an important role in the appearance of AIEE. The electron density difference delocalized over molecules gives rise to small diagonal vibronic coupling constants (VCCs), which suggests that the internal conversion is more suppressed in the solid phase than in the solution phase. The reduction of the off-diagonal VCCs owing to the packing effect is elucidated by vibronic coupling density (VCD) analysis. Pseudo-degeneracy enables fluorescence from the high singlet excited states against Kasha's rule because the electron density difference and the overlap density between the excited states vanish. A Hubbard model of a pseudo-degenerate electronic system is constructed to explain the vanishing mechanism. We propose the following design principle for AIEE: a candidate molecule for AIEE should have pseudo-degenerate adiabatic electronic states in the aggregation phases originating from excimer formation.

Photochromic molecules exhibit photoresponsive variations in their physical properties. For example, energy level, π-conjugation, dipole moment, ionic state and steric conformation can be changed reversibly with alternate UV-visible light illumination. Photochromism has already been proposed for application to various optoelectronic devices. However, practical progress on such applications only became evident after the recent noteworthy developments on organic field-effect transistors (OFETs). This article reviews various applications of such photochromism in organic electronics. First, the photoswitching properties of electrical currents passing through single photochromic molecules are briefly overviewed. Second, effective applications of photochromic reactions in two-dimensional thin film-based diodes are introduced. These studies provided the basis for subsequent developments in OFETs. Finally, recent advances regarding photochromism in OFETs are emphasized as realistic optoelectronic applications.

Photomechanical materials have received increasing attention because of their wide range of potential applications. This paper reports the design of photoresponsive inorganic–organic hybrid molecul...

Ambipolar carrier transport is demonstrated in an optically controllable organic field-effect transistor, where a benzothienothiophene-substituted diarylethene (BTT-DAE) thin film is employed directly as the transistor channel. A closed-ring isomer, which is produced by ultraviolet (UV) light irradiation, allows the carrier injection of both holes and electrons from source-drain electrodes into the BTT-DAE layer. Moreover, alternate UV or visible (VIS) light irradiation induces marked switching in the drain currents caused by reversible photoisomerization between closed-ring (semiconductor) and open-ring (insulator) isomers. The light-driven on/off ratio, which is defined by the ratio of the drain currents in the sample after UV or VIS light irradiation, reaches 240 for hole transport. The value is comparable to the gate-voltage-induced on/off ratio of 160. Our findings, therefore, have a potential to lead to the construction of new optoelectronic devices such as photoreconfigurable logic circuits and light emitting transistors.

An amphiphilic rectangular-shaped photochromic diarylethene bearing two hydrophobic alkyl chains and two hydrophilic tri(ethylene glycol) chains was synthesized, and its photoinduced morphological transformation in water was investigated. Two unexpected phenomena were revealed in the course of the experiments: a re-entrant photoinduced macroscopic morphological transformation and temperature-dependent kinetic products of supramolecular assembly. When the pure closed-ring isomer was dispersed in water, a re-entrant photoinduced morphological transformation, that is, a photoinduced transition from the hydrated phase to the dehydrated phase and then back to the hydrated phase, was observed by optical microscopy upon irradiation with green light at 20 °C; this was interpreted by the V-shaped phase diagram of the LCST transition. The aqueous assembly of the pure closed-ring isomer was controlled by changing the temperature; specifically, rapid cooling to 15 and 5 °C gave J and H aggregates, respectively, as the kinetic products. The thermodynamic product at both temperatures was a mixture of mostly H aggregate with a small amount of J aggregate. This behavior was rationalized by the temperature-dependent potential energy surface of the supramolecular assembly.

Bis(imino nitroxide) bridged by a diarylethene annulated isomer was synthesized and the exchange interaction between the two radicals was determined by the simulation of the ESR spectrum. The exchange interaction was found to be as large as that of the closed-ring isomer, suggesting that the annulated isomer can be used as a highly-conductive molecular wire in molecular electronics.

Self-assembly of amphiphilic photochromic diarylethene having tri(ethylene glycol) monomethyl ether chains was examined in water from the viewpoint of photoinduced morphological transformation and photodriven movement of objects. Self-assembled supramolecular architectures of the amphiphilic diarylethenes undergo photoinduced macroscopic morphological transformation upon alternate irradiation with UV and visible light. The photoreversible morphological change can be rationalized as a photoinduced phase transition between the high- and low-temperature phases of the lower critical solution temperature (LCST) transition. By using a depletion force in a methylcellulose aqueous solution, an amphiphilic diarylethene hierarchically assembled into bundled fibers, which showed shrinking of more than 100 μm under visible light irradiation. Linearly polarized light induced anisotropic growth of the assembled architecture and the diffusive motion of added polystyrene beads was suppressed in the perpendicular direction to the polarized light. The movement of many objects tracing the movement of a UV-irradiation spot was achieved with the assistance of the photogenerated supramolecular architecture.

Structural colored balloons (SCBs) consisting of polymer thin film developed structural color by thin-layer interference on the shell. Thermoresponsive SCBs were prepared with poly(diethylene glycol monomethyl ether methacrylate)- co-poly( N-phenylacrylamide), which shows lower critical solution temperature (LCST) behavior. When cooling gelatin aqueous solution in which osmotic pressure was not operated, only hydration of the copolymer progressed due to LCST transition. The optical path length of the SCB increased due to swelling by water and subsequently decreased due to dissolution. The structural color changed according to the change in optical path length. In cold pure water, in addition to the hydration, osmotic pressure was operated to induce an influx of the outer solvent and the resulting diameter change also affected the shell thickness. The structural color change was analyzed to reveal that the dissolution of the polymer had significant effect on the developed structural color.

Amphiphilic diarylethenes bearing octyloxycarbonyl and N-octylcarbamoyl groups have been designed and synthesized. These ester- and amide-linked compounds form micrometer-sized supramolecular assemblies in water, and these assemblies exhibit photoinduced macroscopic morphological transformations upon alternate irradiation with UV and visible light. The ester-linked diarylethene showed a transformation between colorless spheres and a red-purple hazy fringe, whereas the microspheres of the amide-linked diarylethene showed changes in color, size, and shape, but the spheres did not show division. TEM images revealed that the spheres of the open-ring isomers have coacervate structures, with bicontinuous aqueous and organic phases. The closed-ring isomers of the ester- and amide-linked compounds were found to form nanofibers and thin layers, respectively. These compounds showed absorption spectral shifts at temperatures corresponding to the lower critical solution temperature (LCST) transition. This morphological transformation can be rationalized as the photoinduced phase transition between the high- and low-temperature phases of the LCST transition. These results open up a new avenue for the design of phototransformative supramolecular assemblies based on a combination of photochromism and LCST behavior.

Photoinduced clustering of polystyrene microbeads and photocontrol of their diffusion was achieved in water with the assistance of photoinduced transformation of supramolecular architecture of amphiphilic diarylethene between sphere and fiber states. When a suspension of polystyrene beads containing the sphere state of diarylethene was UV-irradiated from beneath, clustering of the polystyrene beads by thermal convection was observed. The velocity of clustering was dependent on the amount of photogenerated nanofibers that determines the viscosity of the water. Diffusion of the clustered polymer beads was suppressed by the surrounding fibers, but was restored to regular Brownian motion upon irradiation with visible light. It was suggested that the diffusion of the microbeads was controlled by the transformation of aggregates between the more viscous fiber state and the less viscous sphere state. These results provide new insight into the photocontrol of particle motion in fluidic media.

A supramolecular assembly composed of a two-component mixture of amphiphilic diarylethenes, which have octyloxycarbonyl and N-octylcarbamoyl groups, showed a unique macroscopic transformation upon irradiation with UV light and subsequent standing in the dark. Unlike the pure compounds, the assembly was repetitively separated into a blue sphere and a red-purple sparse structure. Both the blue sphere and the sparse structure turned into colorless spheres upon irradiation with visible light and the divided colorless spheres showed the same response to UV and visible light. Phase diagrams based on the change in absorption spectra upon temperature change suggested that the transformation originates from a LCST transition. In the 0.5 : 0.5 mixture, in contrast to the pure compounds, the transition temperature sharply changed at around 50% of the fraction of the closed-ring isomer. TEM imaging showed that the 0.5 : 0.5 mixture with high photoisomerization yield formed a 10 nm-sized network. Judging from the phase diagram and TEM images, the separation is understood as the local phase transition of the regions with a high fraction of the closed-ring isomer.

Optical switching organic field-effect transistors (OFETs) provide a new direction for optoelectronics based on photochromic molecules. However, the patterning of OFETs is difficult because conventional fabrication processes, including lithography and ion etching, inevitably cause severe damage to organic molecules. Here, we demonstrate laser patterning of one-dimensional (1D) channels on an OFET with a photochromic diarylethene (DAE) layer. The main findings are (i) a number of 1D channels can be repeatedly written and erased in the DAE layer by scanning focused ultraviolet and visible light laser beams alternately between the source and drain electrodes, (ii) the conductivity (or resistivity) of the 1D channel can be controlled by the illumination conditions, such as the laser power density and the scan speed, and (iii) it is possible to draw an analogue adder circuit by optically writing 1D channels so that a portion of the channels overlaps and to perform optical summing operations by local laser illumination of the respective channels. These findings will open new possibilities for realizing various optically reconfigurable, low-dimensional organic transistor circuits, which are not possible with conventional thin film OFETs.

Quantum yields can be determined by global fitting of prolonged change of concentration against absorbed photon numbers. Quantum yields of synthesized amphiphilic diarylethene in solution and in suspension were analyzed by the global fitting upon irradiation with UV (365 nm) light. Quantum yields of cyclization and cycloreversion reaction in acetonitrile were obtained as 0.59 and 0.013, respectively using the absolute method. In suspension, quantum yield of cyclization was determined as 0.76 using the relative method. The result indicates that the preferred conformation of the open-ring isomer in the aggregate was antiparallel due to the hydrophilic chains and hydrogen bond.

Self-assembled microstructures of an amphiphilic diarylethene featuring an alkyl chain and triethylene glycol groups showed a photoinduced reversible morphological change in water. Reversible photoisomerization of the core diarylethene gave rise to a reversible morphological transformation between colorless microspheres and colored fibers. When colorless microspheres were irradiated with UV light, colored fibers were formed, and when the colored fibers were irradiated with visible light, the spheres were restored to their original positions where the spheres originally existed. This system showed reversible morphological change through not only photoirradiation but also temperature change. These behaviors can be interpreted as a phase transition between the sphere and fiber states. The dynamic process of the phase transition was monitored by polarized optical microscopy (POM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). It was revealed that the formation of fibers upon UV irradiation occurred radially at the surface of the sphere and the formation of the spheres upon visible-light irradiation occurred at the middle of the fiber. The unique photoinduced mechanical motion provides useful information for the design of sophisticated photoactuators.

The effect of cyano substitution on the fluorescence behavior of 1,2-bis(pyridylphenyl)ethene was investigated. While nonsubstituted 1,2-bis(pyridylphenyl)ethene has fluorescence quantum yield of 97 % in CH2Cl2 solution, cyano-substituted ones fluoresces very little. In contrast, both the no-substituted and the cyano-substituted ones fluoresce moderately in the solid state. The aggregate-induced enhanced emission (AIEE) behavior for the cyano-substituted 1,2-bis(pyridylphenyl)ethene was understood as that the severe quenching of the fluorescence in solution was not operating in the solid state. The fluorescent behaviors in solution and in the solid state are discussed in terms of the emission and the nonradiative decay rate constants.

We demonstrated optical manipulation of single-electron tunneling (SET) by photoisomerization of diarylethene molecules in a metal-insulator-semiconductor (MIS) structure. Stress is placed on the fact that device operation is realized in the practical device configuration of MIS structure and that it is not achieved in structures based on nanogap electrodes and scanning probe techniques. Namely, this is a basic memory device configuration that has the potential for large-scale integration. In our device, the threshold voltage of SET was clearly modulated as a reversible change in the molecular orbital induced by photoisomerization, indicating that diarylethene molecules worked as optically controllable quantum dots. These findings will allow the integration of photonic functionality into current Si-based memory devices, which is a unique feature of organic molecules that is unobtainable with inorganic materials. Our proposed device therefore has enormous potential for providing a breakthrough in Si technology.

A series of nitronyl nitroxide radicals having different lengths of phenylene ethynylene molecular wire were synthesized to investigate the decay constant of p-phenylene ethynylene. By the measurement and simulation of the ESR spectra of the biradicals, it was found that the exchange interaction decreased with a decay constant (β) of 0.39 Å(-1) as the length of the molecule increased. This result indicates that the spin-spin exchange interaction between neutral radicals has a decay constant similar to that of the molecular conductance. This value of the decay constant indicates that a hopping mechanism does not take place in the measurement of the exchange interaction between neutral radicals even when the molecular wire has enough length to show hopping conduction of electrons.

The structural colored balloons (SCBs) composed of poly(vinyl cinnamate) (PVCi) showed solvent responsiveness of structural color by the change of shell thickness along with the size change by osmotic pressure, and the gradual color change could be stopped by UV irradiation. The rate of size change was decreased by the increase of the molecular weight upon photo-cross-linking reaction of PVCi.

Diarylethenes, which have same core structures but have different positions of thiol groups that are bound to gold nanoparticles, were prepared. In one diarylethene, which has two thiol groups at the positions equivalent to 5,5′-positions of di(3-thienyl)ethene, the π-connectivity between two thiol groups increases upon photocyclization, but in the other diarylethene, which has two thiol groups at 2- and 5-positions of one of the 3-thenyl group, the π-connectivity decreases upon photocyclization. The gold nanoparticle networks of these diarylethenes were prepared and the change in conductance was measured upon alternate irradiation with UV and visible light. For two diarylethenes, the direction of the photoswitching was opposite, reflecting the difference in the π-connectivity. The result suggests that the topology of π-conjugation between electrodes is the decisive factor in the conductance of gold nanoparticle network.

Structural colored balloons (SCBs) composed of poly(4-vinylpyridine-co-styrene) (P4VP-PS) exhibited a pH-controlled structural color change in the presence and absence of p-toluenesulfonic acid. The diameter of the SCBs increased and decreased under acidic and neutral conditions, respectively. The different colors exhibited at different pH values supposedly resulted from a change in the shell thickness not only due to the change in the diameter of the SCBs but also due to the uptake of p-toluenesulfonic acid to the pyridyl side chain of P4VP-PS.

A perylene-labeled hyper-branched polymer with a mesogenic shell was observed to migrate toward a field with a large distortion of directors. This polymer was captured by disclination lines of 1/2 strength in its nematic and chiral nematic phases using a confocal fluorescence microscope. In particular, the well-aligned particle array of the hyper-branched polymers was produced by the chiral nematic phase confined in a wedge cell. The hyper-branched polymer with its mesogenic shell was completely dissolved into an isotropic phase. Immediately after a phase transition to the chiral nematic phase, numerous droplets appeared over a wide area owing to phase separation, and the free droplets moved toward the disclination lines via Brownian motion. Finally, the droplets were rapidly attracted to the disclination lines and trapped within them. A fluorescent-labeled hyper-branched polymer with mesogenic shell was captured by the disclination lines of a liquid crystal. In a Grandjean–Cano wedge cell, the particles of the hyper-branched polymer migrated toward the periodically aligned defect line and thus formed a two-dimensional lattice array.

The structural colored balloons (SCBs) consisting of polymer microcapsules showed several structural colors developed by optical thin-layer interference. The SCBs were prepared using a mixture of low- and high-molecular-weight polystyrene to give solvent responsiveness. When the surrounding solvent was transferred from water to the acetone/water mixture using a flow cell, the SCBs swelled at first and shrunk subsequently. The gradual color change of the SCBs was observed along with the size change. The color change accompanying the size change was successfully reproduced by assuming that the total amount of polymer in the thin film does not change. The swelling rate was rationalized by the diffusion of solvent through the shell polystyrene film to the inside of the balloons.

The rate of a bimolecular reaction between a fluorophore and a freely diffusing molecule in the solvent depends on the accessibility of the fluorophore for collision with the molecule. We previously reported that the observation of blinking, caused by the formation of R6G in the excited triplet state ((3) R6G*) and its quenching reaction with O2 , allowed us to monitor the DNA conformational changes between a duplex and a hairpin. However, the small molecular size of O2 hampered sensitive monitoring of the microenvironment changes around R6G. In this study, we control redox blinking by adding a reductant ascorbic acid 2-phosphate (VcP), which converts (3) R6G* into the radical anion form R6G(.-) , and by adding a bulky oxidant FeDTPA. The bimolecular electron-transfer rate between R6G(.-) and bulky FeDTPA was more strongly affected by microenvironment changes around R6G, compared with that between (3) R6G* and the smaller O2 . This allowed us to monitor subtle DNA conformational changes caused by a single different nucleotide.

Ultrasmall-angle synchrotron X-ray scattering measurements showed that a three-dimensional polymer lattice of a few 100 nm order with body-centered cubic O(8-) symmetry was formed in a polymer-stabilized blue phase liquid crystal. We obtained clear experimental evidence that the polymer chains condensed selectively in the disclinations within the blue phase during photo-polymerization of monomers in the blue phase.

International audience; Photochromic diarylethene (DAE) molecules were employed as the channel layer of a field-effect transistor, where the drain current was effectively modulated by the reversible phase transition between a semiconductor (closed-ring) and an insulator (open-ring) under ultraviolet or visible light irradiation. Our goal was the further improvement of optical switching properties by interface engineering. First, we reduced the hole injection barrier by introducing an a -sexithiophene (6T) thin film at the interface between the source–drain electrodes and the DAE channel layer. As a result, the threshold voltage of the DAE-FETs was greatly reduced from -64 to -4 V. Second, we improved the optical switching performance by the surface treatment of a SiO 2 gate insulator with poly(methyl methacrylate) (PMMA). The drain current was unchanged even after 10 cycles of optical switching in contrast to the rapid degradation found with untreated DAE transistors. The combination of these improvements and interdigitated source–drain electrodes eventually resulted in a light irradiation driven on/off ratio of over 10^3. Significantly, the light-induced on/off ratio was comparable to that driven by an electrical field, which satisfies the requirement for industrial optical applications. Our findings will provide useful ways of realizing high-performance optical switching transistors.

Bis(3-thienyl)perfluorocyclopentenes containing partially fluorinated thiophene rings were synthesized and their behaviors examined. Dithienylethenes containing chlorinated thiophene rings were also prepared as reference compounds. The absorption maxima of the closed-ring isomers, their thermal stabilities, and their quantum yields varied depending on the substitution position. The absorption maxima showed a red shift upon fluorine substitution at the 2- or 4-positions of the thiophene ring, whereas a blue shift was observed upon substitution at the 5-position. This shift was explained by the shape of the HOMO and LUMO and was well reproduced by theoretical calculations using time-dependent density-functional theory (TD-DFT). The cycloreversion quantum yield of the closed-ring isomer of 2-fluorine-substituted 1,2-bis(2-fluoro-3-thienyl)perfluorocyclopentene was about 130 times smaller than that of the closed-ring isomer of 5-fluorine-substituted 1,2-bis(5-fluoro-2-methyl-3-thienyl)perfluorocyclopentene. This low quantum yield was attributed to the change of the π-conjugation mode in the closed-ring isomer. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Bis(3-thienyl)- and bis(2-thienyl)ethenes having nitronyl nitroxide radicals at both ends of the molecules were synthesized. Bis(3-thienyl)ethene diradicals underwent a reversible photochromic reaction by irradiation with UV and visible light. Photoswitching of intramolecular magnetic interaction was proved by EPR spectroscopy. By choosing an appropriate spacer, the intramolecular exchange interaction in the closed-ring isomer was detected to be more than 150 times larger than that in the open-ring isomer. In the case of bis(2-thienyl)ethene diradicals, the photocyclization reaction was prohibited, and only the cycloreversion reaction took place by irradiation with visible light. The closed-ring isomers of the diradicals were synthesized from the closed-ring isomers of the precursors. From the analysis of the EPR spectra of the system with an appropriate spacer, it was found that on/off switching behavior was reversed by changing the substitution position of the thiophene rings to the ethene moiety from t...

Photochromic reactivity of a dithienylethene dimer, 5-(2-(3,4-dimethyl-2-thienyl))-3,3,4,4,5,5-hexafluorocyclopent-1-enyl-2-(2-(2,4-dimethyl-3-thienyl))-3,3,4,4,5,5-hexafluorocyclopent-1-enyl-3,4-dimethylthiophene, was studied in solution as well as in the crystalline phase. In solution two kinds of closed-ring form isomers were reversibly produced upon irradiation with ultraviolet light, while in the crystalline phase only one kind of closed-ring form isomer was produced. The different reactivity was attributed to the difference in the distance between two reactive centers in the crystal.

A substituent effect of asymmetric diarylethene annulated isomer on their chiroptical properties was investigated by means of theoretical and experimental approaches. The absolute configuration of the annulated isomer was determined by X-ray structural analysis and DFT calculation. The TD–DFT calculation successfully reproduced not only the sign but also the shape and magnitude of experimental CD spectrum by considering the Boltzmann-weighted average of four atrop-isomers. A fragment decomposition (FD) analysis of rotatory strength clearly revealed a noteworthy effect; the tilting motion concomitant with the rotating motion of the substituent affects the sign and magnitude of CD signals. It was found that even when the absolute structure of the chiral core moiety does not change, the slight motion of the substituent can trigger the inversion of the CD signal.

The fatigue mechanism of photochromic 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene was studied in hexane solution. Upon irradiation with ultraviolet light, two kinds of by-products were produced in addition to normal photochromic reactions. The major by-product was isolated by HPLC, and was characterized by 1H NMR and absorption spectroscopies and X-ray crystallographic analysis. A minor by-product was also isolated and analyzed with a mass spectrometer. Based on the molecular structural analysis a possible photofatigue mechanism of the dithienylethene was proposed.

We achieved drain-current switching of diarylethene-channel field-effect transistors with light- and electric-field effects. The drain current was reversibly changed by alternating ultraviolet and visible light irradiation. Stress is placed on the fact that the on/off ratio realized by light irradiation was 1 × 10(2) (1 × 10(4)%) and this value is much larger than those in other photochromism-based transistors. These results indicate that the drain current was effectively controlled by light irradiation. Furthermore, the on and off states modulated by light were maintained without light irradiation even after 1 week, exhibiting that our transistor works as an optical memory. We clarified that the light-driven modulation can be attributed to the transformation in the π-conjugation system accompanied by photoisomerization. These findings have the potential to attain high-performance optoelectrical organic devices including optical sensors, optical memory, and photoswitching transistors.

The self-assembled structure of alkoxy- and N-alkylcarbamoyl-substituted zinc-tetraphenylporphyrin at the liquid-highly oriented pyrolytic graphite (HOPG) interface was observed by using scanning tunneling microscopy. The alkoxy porphyrin showed a phase transition from face-on to edge-on ordering. The phase transition requires the close-packed structure of alkoxy porphyrin. The chronological change of the ordering was traced to show the existence of several types of Ostwald ripening including two-step phase transition from small edge-on to face-on and then further to edge-on orderings. On the other hand, the N-alkylcarbamoyl porphyrin showed persistent edge-on ordering, and the ordering was analyzed by the Moire pattern. Although the edge-on ordering is observed only in the nonpolar solvent, the orderings have potential applications in the charge and energy transfer.

Tetraphenylporphyrin (TPP) rhodium chlorides coordinated by planar and twisted 4-phenylpyridine derivatives were synthesized. An STM image was taken by a 2-D phase separation technique and the conductance was evaluated. Difference in apparent height between these phenylpyridines reflects the conductance ratio of ligands.

Unusual blue shift of the absorption maxima of two nitronyl nitroxide attached diarylethene through phenyl units (DAE-phe-NN) with increasing number of phenyl units is examined by time dependent density functional theory (TDDFT). The extended π-conjugation between nitronyl nitroxide and diarylethene is rather suppressed by the bridge phenyl units. In comparison, the red shift found in two nitronyl nitroxide attached diarylethenes through thiophene units (DAE-thio-NN) with increasing number of thiophene units is due to the longer π-conjugation induced by smaller dihedral angles between diarylethene and bridge and between bridges.

1-Cyano-1,2-bis(biphenyl)ethene (CNBE) derivatives with a hexa(ethylene glycol) group as an amphiphilic side chain were synthesized and the self-assembling character and fluorescence behavior were investigated. The amphiphilic derivatives showed aggregate-induced enhanced emission (AIEE) in water and in the solid state. The fluorescence quantum yield increased as the rigidity of the aggregates increased (i.e., in ethyl acetate

Oligophenylene molecular rods with bicyclo[2.2.2]octane having two nitronyl nitroxide radicals were synthesized to investigate the decay constant of p-phenylene. By the measurement and simulation of the ESR spectra of the biradicals with different rod length, it was found that the exchange interaction was decreased with the decay constant β of 0.51 ± 0.01 A(-1). This result indicates that the spin-spin exchange interaction between neutral radicals has a decay constant similar to the molecular conductance.

The three-dimensional structure of polymer-stabilized blue phase with the order of optical wavelength was nondestructively investigated by a confocal laser scanning microscope. The periodical patterns corresponding to the bcc lattice were observed not only on the surface but also in the internal region. The visualization mechanism was expected to be back scattering caused by liquid crystal order.