Co-reporter:Hiromu Kubo, Takashi Hirose, and Kenji Matsuda
Organic Letters April 7, 2017 Volume 19(Issue 7) pp:
Publication Date(Web):March 30, 2017
DOI:10.1021/acs.orglett.7b00548
The effect of different substituents on the fluorescence properties of [5]helicene derivatives was investigated in terms of molecular orbital symmetry. Unsubstituted [5]helicene is nonemissive due to the symmetry-forbidden S1 → S0 transition. However, the fluorescence emission rate constant (kf) of [5]helicenes is efficiently increased by removing the orbital degeneracy involved in the S1 → S0 transition. As a result, we achieved a [5]helicene derivative exhibiting a high fluorescence quantum yield (Φf = 0.23) and short emission lifetime (⟨τf⟩ = 1.5 ns), which is in marked contrast to unsubstituted [5]helicene (Φf = 0.04 and ⟨τf⟩ = 26 ns).
Co-reporter:Akira Sakaguchi, Kenji Higashiguchi, Hajime Yotsuji, and Kenji Matsuda
The Journal of Physical Chemistry B April 27, 2017 Volume 121(Issue 16) pp:4265-4265
Publication Date(Web):March 27, 2017
DOI:10.1021/acs.jpcb.7b00901
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.
Co-reporter:Tohru Tsuruoka, Ryoma Hayakawa, Kazuyoshi Kobashi, Kenji Higashiguchi, Kenji Matsuda, and Yutaka Wakayama
Nano Letters 2016 Volume 16(Issue 12) pp:7474-7480
Publication Date(Web):November 15, 2016
DOI:10.1021/acs.nanolett.6b03162
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.Keywords: analogue adder circuit; diarylethene; laser patterning; one-dimensional channel; Organic field-effect transistor; photochromism;
Co-reporter:Takashi Hirose, Natsuki Ito, Hiromu Kubo, Tohru Sato and Kenji Matsuda
Journal of Materials Chemistry A 2016 vol. 4(Issue 14) pp:2811-2819
Publication Date(Web):26 Jan 2016
DOI:10.1039/C5TC03675E
The surrounding environment of a molecular fluorophore is one of the most important determining factors in luminescence properties, such as the emission quantum yield, the lifetime of the excited state, and the color of luminescence. In this work, we investigate the relationship between the self-assembled structure and the fluorescence properties of [5]helicene derivatives in the solution phase. A [5]Helicene derivative bearing the tri(ethylene glycol) group formed spherical aggregates in aqueous media and that bearing the (3,4,5-trioctyloxyphenyl)carbamoyl group formed fibrous aggregates in apolar solvent. Analysis based on the radiative (kf) and non-radiative (knr) rate constants suggests that (1) an aggregation-induced suppression of fluorescence observed in aqueous media is attributed to the decrease of kf, (2) an aggregation-induced enhancement of fluorescence observed for fibrous aggregates formed in an apolar solvent is associated with the suppression of knr, (3) [5]helicenes become almost non-fluorescent especially in a polar solvent by introducing an appropriate donor substituent due to a charge-transfer (CT) type property in the lowest energy excited state, and (4) the strong quenching effect due to the CT-type excitation can be efficiently alleviated by several approaches, such as by forming aggregates with an appropriate self-assembly motif or by controlling the energy level of molecular orbitals.
Co-reporter:Yosuke Uchida, Takashi Hirose, Takuya Nakashima, Tsuyoshi Kawai, and Kenji Matsuda
Organic Letters 2016 Volume 18(Issue 9) pp:2118-2121
Publication Date(Web):April 27, 2016
DOI:10.1021/acs.orglett.6b00747
A 13,13′-bibenzo[b]perylenyl derivative—an axially chiral π-extended compound in which two perylene subunits fused to 1,1′-binaphthyl scaffold—has been synthesized from 1,8-dibromophenanthrene using an anionic cyclodehydrogenation reaction in the presence of potassium metal as the key step. The pair of enantiomers can be separated by chiral high-performance liquid chromatography (HPLC), which showed a strong circular dichroism (CD) (Δε = 330 M–1 cm–1 at 449 nm, |gCD| = 5.8 × 10–3 at 453 nm), high fluorescence quantum yield (Φf = 64%), and strong circular polarized luminescence (CPL) (|gCPL| = 5 × 10–3 at 454 nm) in solution phase.
Co-reporter:Shohei Nishizawa, Arnaud Fihey, Denis Jacquemin, Kenji Matsuda
Chemical Physics Letters 2016 Volume 659() pp:258-262
Publication Date(Web):16 August 2016
DOI:10.1016/j.cplett.2016.07.027
Highlights
- •
The exchange interaction J and the first hyperpolarizability β for DAEs were calculated.
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The direction of change is always logically related to the π-conjugation pathway.
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The switching directions of J and β are different for some DAEs.
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The SE values of β are smaller than the SE values of J for all molecules.
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Oxidizing the sulfur atoms of the DAEs yields small variations on SE of J and β.
Co-reporter:Naoki Maeda
The Journal of Physical Chemistry C 2016 Volume 120(Issue 17) pp:9317-9325
Publication Date(Web):April 6, 2016
DOI:10.1021/acs.jpcc.6b02115
Photoresponsive behavior of systems in equilibrium at the liquid/solid interface can be modulated through the design of photochromic core structures and the process of self-assembly. In this study, we investigated the effects of altering the substitution position of a thienyl group on two-dimensional (2-D) molecular ordering composed of photochromic diarylethenes (DAEs) at a liquid/highly oriented pyrolytic graphite (HOPG) interface using scanning tunneling microscopy (STM). We found that both the open- and the closed-ring isomers of a 3-thienyl-type DAE formed stripe-patterned orderings on a HOPG substrate at similar concentrations and that the process of self-assembly on a 2-D surface was highly cooperative for both isomers. In the case of 2-thienyl-type DAE, similar stripe-patterned ordering was observed only for the open-ring isomer, but no ordering was observed for the closed-ring isomer. Upon irradiation with UV and visible light, reversible three-state photoswitching over the formation/disappearance of 2-D ordering was observed using the 3-thienyl-type DAE. The instability of the ordering of the 2-thienyl-type closed-ring isomer was rationalized by the bend angle of the DAE core framework. Fundamental understanding of the relationship between the photoresponsive behavior of 2-D molecular ordering and molecular structures has been deepened through quantitative analyses of the concentration dependence of surface coverage and computational studies that included molecular mechanics/molecular dynamics (MM/MD) calculations.
Co-reporter:Kenji Higashiguchi, Jun Imai, and Kenji Matsuda
Langmuir 2016 Volume 32(Issue 19) pp:4945-4951
Publication Date(Web):April 25, 2016
DOI:10.1021/acs.langmuir.6b00607
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.
Co-reporter:Taichi Toyama; Kenji Higashiguchi; Tsukuru Nakamura; Hidehiro Yamaguchi; Eriko Kusaka
The Journal of Physical Chemistry Letters 2016 Volume 7(Issue 11) pp:2113-2118
Publication Date(Web):May 18, 2016
DOI:10.1021/acs.jpclett.6b00993
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.
Co-reporter:Kenji Higashiguchi; Genki Taira; Jun-ichiro Kitai; Takashi Hirose
Journal of the American Chemical Society 2015 Volume 137(Issue 7) pp:2722-2729
Publication Date(Web):February 4, 2015
DOI:10.1021/ja512924q
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.
Co-reporter:Ryoma Hayakawa, Matthieu Petit, Kenji Higashiguchi, Kenji Matsuda, Toyohiro Chikyow, Yutaka Wakayama
Organic Electronics 2015 Volume 21() pp:149-154
Publication Date(Web):June 2015
DOI:10.1016/j.orgel.2015.03.011
•We improved the optical switching properties in a diarylethene-channel transistor using interface engineering.•The insertion of 6T thin film was effective for reducing the threshold voltage.•The surface modification of a gate insulator with a PMMA layer suppressed degradation in photoswitching.•We eventually achieved an on/off ratio realized by light irradiation of 103 (105%).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 α-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 SiO2 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 103. 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.
Co-reporter:Soichi Yokoyama;Dr. Takashi Hirose ; Kenji Matsuda
Chemistry - A European Journal 2015 Volume 21( Issue 39) pp:
Publication Date(Web):
DOI:10.1002/chem.201583901
Co-reporter:Soichi Yokoyama;Dr. Takashi Hirose ; Kenji Matsuda
Chemistry - A European Journal 2015 Volume 21( Issue 39) pp:
Publication Date(Web):
DOI:10.1002/chem.201503114
Abstract
Invited for the cover of this issue are Soichi Yokoyama, Takashi Hirose, and Kenji Matsuda at Kyoto University. The image depicts cooperative self-assembly of diarylethene molecules at solid/liquid interface and its phototriggered transformation. Read the full text of the article at 10.1002/chem.201500707.
Co-reporter:Soichi Yokoyama;Dr. Takashi Hirose ; Kenji Matsuda
Chemistry - A European Journal 2015 Volume 21( Issue 39) pp:13569-13576
Publication Date(Web):
DOI:10.1002/chem.201500707
Abstract
An appropriate understanding of the process of self-assembly is of critical importance to tailor nanostructured order on 2D surfaces with functional molecules. Photochromic compounds are promising candidates for building blocks of advanced photoresponsive surfaces. To investigate the relationship between molecular structure and the mechanism of ordering formation, 2-thienyl-type diarylethenes with various lengths of alkyl side chains linked through an amide or ester group were synthesized. Their self-assemblies at a liquid/solid interface were investigated by scanning tunneling microscopy (STM). The concentration dependence of the surface coverage was analyzed by using a cooperative model for a 2D surface based on two characteristic parameters: the nucleation equilibrium constant (Kn) and the elongation equilibrium constant (Ke). The following conclusions can be drawn. 1) The concentration at which a stable 2D molecular ordering is observed by STM exponentially decreases with increasing length of the alkyl chain. 2) Compounds bearing amide groups have higher degrees of cooperativity in self-assembly on 2D surfaces (i.e., σ, which is defined as Kn/Ke) than compounds with ester groups. 3) The self-assembly process of the open-ring isomer of an ester derivative is close to isodesmic, whereas that of the closed-ring isomer is cooperative because of the difference in equilibrium constants for the nucleation step (i.e., Kn) between the two isomers.
Co-reporter:Dr. Denis Frath;Dr. Takeshi Sakano;Yohei Imaizumi;Soichi Yokoyama;Dr. Takashi Hirose ; Kenji Matsuda
Chemistry - A European Journal 2015 Volume 21( Issue 32) pp:
Publication Date(Web):
DOI:10.1002/chem.201583262
Co-reporter:Dr. Denis Frath;Dr. Takeshi Sakano;Yohei Imaizumi;Soichi Yokoyama;Dr. Takashi Hirose ; Kenji Matsuda
Chemistry - A European Journal 2015 Volume 21( Issue 32) pp:11350-11358
Publication Date(Web):
DOI:10.1002/chem.201500804
Abstract
Stimulus control over 2D multicomponent molecular ordering on surfaces is a key technique for realizing advanced materials with stimuli-responsive surface properties. The formation of 2D molecular ordering along with photoisomerization was monitored by scanning tunneling microscopy at the octanoic acid/highly oriented pyrolytic graphite interface for a synthesized amide-containing diarylethene, which underwent photoisomerization between the open- and closed-ring isomers and also a side-reaction to give the annulated isomer. The nucleation (Kn) and elongation (Ke) equilibrium constants were determined by analysis of the concentration dependence of the surface coverage by using a cooperative model at the liquid/solid interface. It was found that the annulated isomer has a very large equilibrium constant, which explains the predominantly observed ordering of the annulated isomer. It was also found that the presence of the closed-ring isomer induces cooperativity into the formation of molecular ordering composed of the open-ring isomer. A quantitative analysis of the formation of ordering by using the cooperative model has provided a new view of the formation of 2D multicomponent molecular ordering.
Co-reporter:Dr. Takashi Hirose;Yohei Tsunoi;Yuya Fujimori ; Kenji Matsuda
Chemistry - A European Journal 2015 Volume 21( Issue 4) pp:1637-1644
Publication Date(Web):
DOI:10.1002/chem.201404745
Abstract
The fluorescence enhancement effect of covalently fixed fluorescent chromophores has been investigated by means of kinetic analysis of decay rate constants and theoretical calculations. Derivatives of 1-cyano-1,2-diphenylethene dimer have a distorted cyclic structure when both ends are clipped with two naphthalene-1,8-diyl linker units. In contrast to the reference monomer derivative, which exhibits only slight fluorescence in solution (Φf<0.01, τf<0.1 ns), the dimer derivative shows high fluorescence quantum yield (Φf=0.55) and long lifetime (τf=20.6 ns) in dilute solution owing to suppression of the nonradiative decay process (knr=0.022 ns−1). A V-shaped derivative with a covalent linker on one side showed moderate quantum yield and lifetime (Φf=0.12, τf=4.9 ns). According to the wavelength shifts of the absorption/fluorescence bands and theoretical calculations by time-dependent density functional theory (TD-DFT), we propose an H-aggregate-type excimer interaction.
Co-reporter:Soichi Yokoyama, Takashi Hirose, and Kenji Matsuda
Langmuir 2015 Volume 31(Issue 23) pp:6404-6414
Publication Date(Web):May 25, 2015
DOI:10.1021/acs.langmuir.5b01404
We have investigated photoinduced ordering transformation of a photochromic terthiophene derivative by scanning tunneling microscopy (STM) at the trichlorobenzene (TCB)/highly oriented pyrolytic graphite (HOPG) interface. The open-ring and annulated isomers of the terthiophene formed two-dimensional molecular orderings with different patterns while the closed-ring isomer did not form any ordering. The ordering of the open-ring isomer exhibited polymorphism depending on the concentration of supernatant solution. Upon UV light irradiation to a solution of the open-ring isomer or the closed-ring isomer, ordering composed of the annulated isomer was irreversibly formed. Upon visible light irradiation or thermal stimulus to the closed-ring isomer, the two kinds of polymorph composed of the open-ring isomer were formed due to the polymorphism. By controlling photochromism and polymorphism among four states made of three photochemical isomers, four-state three-step transformation was achieved by in situ photoirradiation from a solution of the closed-ring isomer (no ordering) into the ordering composed of the open-ring isomer (ordering α and β) followed by the orderings composed of the annulated isomer (ordering γ).
Co-reporter:Shohei Nishizawa
The Journal of Physical Chemistry C 2015 119(34) pp: 20169-20178
Publication Date(Web):August 3, 2015
DOI:10.1021/acs.jpcc.5b06738
The switching efficiency (SE) of the intramolecular exchange interaction J between the open- and the closed-ring isomers of diarylethenes (DAEs) was investigated using DFT calculations of DAE biradicals with different core structures: DAEs with 3-thienyl, thiophene-S,S-dioxide-3-yl, 2-thienyl, or thiophene-S,S-dioxide-2-yl rings. The SE of DAE with a 3-thienyl ring is calculated to be around 400-fold, which is the largest among the four calculated DAEs. The decay constant β of the exchange interaction J for the DAE molecular wires was evaluated by calculating J for biradicals with different lengths of wires. For the wires of the closed-ring isomers of DAE with 3-thienyl- and thiophene-S,S-dioxide-3-yl rings, which are supposed to take a quinoid structure, allyl nitronyl nitroxide radical was successfully employed. The calculated β values showed a significant difference between the open- and the closed-ring isomers, and this difference of β is considered to be the origin of photoswitching of J. The difference of β upon isomerization, Δβ, is in good agreement with SE, and the largest Δβ was obtained for the DAE with a 3-thienyl ring. We can understand the switching of J as the switching of electron tunneling efficiency β between the open- and the closed-ring isomers.
Co-reporter:Shohei Nishizawa
The Journal of Physical Chemistry C 2015 Volume 119(Issue 9) pp:5117-5121
Publication Date(Web):February 4, 2015
DOI:10.1021/jp511608w
The difference in the decaying behavior of the exchange interaction between quinoid and aromatic molecular wires was investigated by means of density functional theory calculations. The biradical quinoid structure was realized when the molecular wire consists of thiophene-S,S-dioxide and allyl nitronyl nitroxide radical. While the calculated decay constant (β) for oligothiophene was 0.23 Å–1, the obtained β value for the quinoid structure of oligothiophene-S,S-dioxide was 0.09 Å–1; this finding suggested that the quinoid molecular wire had a smaller β value than the aromatic wire. It was also found that β decreases upon oxidation of the sulfur atom in the oligothiophene due to an increase in its olefinic nature. The quinoid molecular wire made of thiophene-S,S-dioxide can be thus considered as a suitable system for the charge and spin transport in molecular electronics and spintronics.
Co-reporter:Nobuhiko Nishitani;Dr. Takashi Hirose ; Kenji Matsuda
Chemistry – An Asian Journal 2015 Volume 10( Issue 9) pp:
Publication Date(Web):
DOI:10.1002/asia.201580901
Co-reporter:Nobuhiko Nishitani;Dr. Takashi Hirose ; Kenji Matsuda
Chemistry – An Asian Journal 2015 Volume 10( Issue 9) pp:1926-1931
Publication Date(Web):
DOI:10.1002/asia.201500453
Abstract
Formation of a hydrogen-bond network via an amide group is a key driving force for the nucleation–elongation-type self-assembly that is often seen in biomolecules and artificial supramolecular assemblies. In this work, rod-coil-like aromatic compounds bearing an amide (1 a–3 a) or urea group (1 u–3 u) were synthesized, and their self-assemblies on a 2-D surface were investigated by scanning tunneling microscopy (STM). According to the quantitative analysis of the concentration dependence of the surface coverage, it was revealed that the strength of the hydrogen bond (i.e., amide or urea) and the number of non-hydrogen atoms in a molecular component (i.e., size of core and length of alkyl side chain) play a primary role in determining the stabilization energy during nucleation and elongation processes of molecular ordering on the HOPG surface.
Co-reporter:Soichi Yokoyama, Takashi Hirose and Kenji Matsuda
Chemical Communications 2014 vol. 50(Issue 45) pp:5964-5966
Publication Date(Web):16 Jan 2014
DOI:10.1039/C3CC48895K
A photoresponsive self-assembly on a 2-D surface was investigated by scanning tunnelling microscopy (STM). The open-ring isomer of a diarylethene derivative showed an abrupt ordering formation at a critical concentration, which was successfully reproduced by a cooperative model based on Langmuir-type adsorption.
Co-reporter:Natsuki Ito, Takashi Hirose, and Kenji Matsuda
Organic Letters 2014 Volume 16(Issue 9) pp:2502-2505
Publication Date(Web):April 21, 2014
DOI:10.1021/ol5008718
Photocyclodehydrogenation is a key reaction to synthesize helicenes; however, because of overannulation, it is not applicable to the synthesis of [5]helicene. Introduction of a cyano group was found to remove the orbital degeneracy of the low-lying unoccupied MOs; consequently, the lowest excitation comprises a single transition involving the C2-antisymmetric MO. Therefore, the problematic overannulation can be effectively suppressed. Moreover, in combination with the Knoevenagel reaction, a one-pot synthesis of 5,10-dicyano[5]helicene with 67% yield was accomplished.
Co-reporter:Suguru Nishio;Dr. Kenji Higashiguchi; Kenji Matsuda
Asian Journal of Organic Chemistry 2014 Volume 3( Issue 6) pp:686-690
Publication Date(Web):
DOI:10.1002/ajoc.201402024
Abstract
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.
Co-reporter:Takashi Hirose, Yuki Inoue, Jun-ya Hasegawa, Kenji Higashiguchi, and Kenji Matsuda
The Journal of Physical Chemistry A 2014 Volume 118(Issue 6) pp:1084-1093
Publication Date(Web):January 20, 2014
DOI:10.1021/jp4122694
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.
Co-reporter:Ryoma Hayakawa, Kenji Higashiguchi, Kenji Matsuda, Toyohiro Chikyow, and Yutaka Wakayama
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 21) pp:11371
Publication Date(Web):October 7, 2013
DOI:10.1021/am403616m
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.Keywords: metal−insulator−semiconductor; optical manipulation; photochromic quantum dot; single-electron tunneling;
Co-reporter:Ryoma Hayakawa, Kenji Higashiguchi, Kenji Matsuda, Toyohiro Chikyow, and Yutaka Wakayama
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 9) pp:3625
Publication Date(Web):April 2, 2013
DOI:10.1021/am400030z
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 × 102 (1 × 104%) 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.Keywords: optical and electrical gates; photochromic channel layer; thin film transistor;
Co-reporter:Takashi Hirose and Kenji Matsuda
Organic & Biomolecular Chemistry 2013 vol. 11(Issue 6) pp:873-880
Publication Date(Web):29 Nov 2012
DOI:10.1039/C2OB27049H
Photochromic diarylethene is a promising candidate not only for optical memory and switching units in molecular devices, but also as a photoresponsive building block that can regulate supramolecular architectures because of its characteristic changes in the flexibility of the framework and delocalization of π-electrons, along with its photoisomerization ability. Amphiphilic photochromic compounds with oligo-(ethylene glycol) side chains show good solubility in water, and self-assemble into nanostructures in aqueous media. Asymmetric introduction of a methyl group can induce a helical preference in the supramolecular structure, and the photoswitching behaviour of supramolecular chirality was defined by circular dichroism (CD) spectroscopy and density functional theory (DFT) calculations. The effective position of an asymmetric group to induce supramolecular chirality is also discussed. In addition, the self-assemblies of diarylethene derivatives in water show photoresponsive lowest critical solution temperature (LCST). The open- and closed-ring isomers show LCST transitions at different temperatures. In particular, the difference in LCST becomes prominent when amide groups are introduced at the root of hydrophilic side chains. This is attributed to intermolecular hydrogen bonds formed by the amide groups in the hydrophobic region of the supramolecular structure in water.
Co-reporter:Shohei Nishizawa, Jun-ya Hasegawa, Kenji Matsuda
Chemical Physics Letters 2013 Volume 555() pp:187-190
Publication Date(Web):3 January 2013
DOI:10.1016/j.cplett.2012.10.092
Abstract
The nature of π-conjugated wire is characterized by the decay constant β of electron tunneling. To evaluate the decay constant, intramolecular magnetic exchange interaction was calculated by density functional theory for organic biradicals: nitronyl nitroxide and verdazyl were chosen for the radical substituent and oligophenylene and oligo(phenylene ethynylene) were chosen for the wire. For phenylene and phenylene ethynylene units, β was calculated to be 0.42 Å−1 and 0.24 Å−1, respectively, and the β value was independent of radical species. The obtained β values are in good agreement with the experimental value of the molecular tunneling conductance.
Co-reporter:Masataka Shinomiya, Kenji Higashiguchi, and Kenji Matsuda
The Journal of Organic Chemistry 2013 Volume 78(Issue 18) pp:9282-9290
Publication Date(Web):August 28, 2013
DOI:10.1021/jo4015062
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.
Co-reporter:Shohei Nishizawa ; Jun-ya Hasegawa
The Journal of Physical Chemistry C 2013 Volume 117(Issue 49) pp:26280-26286
Publication Date(Web):November 4, 2013
DOI:10.1021/jp407452p
The decay constant β of π-conjugated molecular wire corresponds to the efficiency of electron tunneling through the molecule. We have calculated β values of intramolecular magnetic exchange interactions by density functional theory for organic bis(nitronyl nitroxide)s that have several molecular wire units, namely, oligo-p-phenylene (OPP), oligophenylene ethynylene (OPE), oligophenylene vinylene (OPV), oligophenylene imine (OPI), bicyclo[1.1.1]pentane oligomer (BCP), β,meso,β-triply fused porphyrin oligomer (TFP), and meso,meso-linked porphyrin oligomer (MLP). For OPP, OPE, OPV, OPI, BCP, TFP, and MLP, β was calculated to be 0.41, 0.25, 0.22, 0.32, 0.77, 0.03, and 0.65 Å–1, respectively. The obtained β values are in good agreement with the experimental value of the molecular tunneling conductance, suggesting similarity of the mechanism between exchange interaction and molecular conductance. This method can be used to estimate the efficiency of electron tunneling through the molecular wire.
Co-reporter:Masafumi Inoue, Kenji Higashiguchi, and Kenji Matsuda
Langmuir 2013 Volume 29(Issue 23) pp:7047-7051
Publication Date(Web):May 23, 2013
DOI:10.1021/la400534s
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.
Co-reporter:Kenji Higashiguchi, Masafumi Inoue, Tomohiro Oda, and Kenji Matsuda
Langmuir 2012 Volume 28(Issue 12) pp:5432-5437
Publication Date(Web):March 1, 2012
DOI:10.1021/la3006234
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.
Co-reporter:Takeshi Sakano;Dr. Jun-ya Hasegawa;Dr. Kenji Higashiguchi ; Kenji Matsuda
Chemistry – An Asian Journal 2012 Volume 7( Issue 2) pp:394-399
Publication Date(Web):
DOI:10.1002/asia.201100587
Abstract
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 Moiré pattern. Although the edge-on ordering is observed only in the nonpolar solvent, the orderings have potential applications in the charge and energy transfer.
Co-reporter:Takeshi Sakano, Kenji Higashiguchi and Kenji Matsuda
Chemical Communications 2011 vol. 47(Issue 29) pp:8427-8429
Publication Date(Web):24 Jun 2011
DOI:10.1039/C1CC12041G
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.
Co-reporter:Dr. Takashi Hirose;Dr. Kenji Higashiguchi ; Kenji Matsuda
Chemistry – An Asian Journal 2011 Volume 6( Issue 4) pp:1057-1063
Publication Date(Web):
DOI:10.1002/asia.201000824
Abstract
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<in water<in the solid state). As determined from measurements of fluorescence spectra, fluorescence quantum yields, and fluorescence lifetimes, a key factor for the enhanced emission is suppression of the nonradiative decay process arising from restricted molecular motion. Additionally, the difference in the emission rate constant is not negligible and can be used to interpret the difference in fluorescence quantum yield in water and in the solid state.
Co-reporter:Kenji Higashiguchi, Koji Yumoto, and Kenji Matsuda
Organic Letters 2010 Volume 12(Issue 22) pp:5284-5286
Publication Date(Web):October 20, 2010
DOI:10.1021/ol102339m
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 Å−1. This result indicates that the spin−spin exchange interaction between neutral radicals has a decay constant similar to the molecular conductance.
Co-reporter:Takashi Hirose and Kenji Matsuda
Chemical Communications 2009 (Issue 39) pp:5832-5834
Publication Date(Web):08 Sep 2009
DOI:10.1039/B910531J
A 1-cyano-1,2-bis(biphenyl)ethene derivative having hexa(ethylene glycol) groups as amphiphilic side chains showed aggregate-induced enhanced emission in water; upon heating the intensity of the enhanced emission was attenuated in a lower temperature range than the temperature range where exciton interaction is still effective.
Co-reporter:Takashi Hirose, Masahiro Irie and Kenji Matsuda
New Journal of Chemistry 2009 vol. 33(Issue 6) pp:1332-1334
Publication Date(Web):24 Feb 2009
DOI:10.1039/B822880A
A photochromic diarylethene derivative having chiral polyethylene glycol side chains at the reactive carbon atoms was synthesized. The diarylethene showed a photochromic reaction upon irradiation with UV and visible light in both ethyl acetate and water. The open- and the closed-ring isomers showed a non-exciton-coupled-type of CD spectrum, and the compound underwent a diastereoselective cyclization reaction.
Co-reporter:Takashi Hirose;Masahiro Irie
Chemistry – An Asian Journal 2009 Volume 4( Issue 1) pp:58-66
Publication Date(Web):
DOI:10.1002/asia.200800340
Abstract
Photochromic diarylethene derivatives having different lengths and numbers of poly(ethylene glycol) side chains were synthesized and their photochromic property and self-assembling behavior were investigated. The self-assembling behavior of the derivatives strongly depends upon the ratio between the hydrophobic core and the amphiphilic side chain. According to UV/Vis absorption spectroscopy, CD spectroscopy, and dynamic light scattering experiments, these derivatives showed different size distribution of the assembled structures and different solubility in water. The intensity of the induced CD signal, which was observed in the closed-ring isomer, was the largest for the molecule having two hexaethylene glycol side chains. The relationship between the core-chain ratio and regularity of the self-assembled structure has been investigated.
Co-reporter:Kenji Matsuda ; Hidehiro Yamaguchi ; Takeshi Sakano ; Masumi Ikeda ; Naoki Tanifuji ;Masahiro Irie
The Journal of Physical Chemistry C 2008 Volume 112(Issue 43) pp:17005-17010
Publication Date(Web):October 7, 2008
DOI:10.1021/jp807479g
The relationship between molecular conductance and molecular structure is an important issue in molecular electronics. Photochromic molecules can interconvert their molecular structures by light, so that the molecular conductance should be photocontrolled. According to this strategy the networks composed of photochromic diarylethene dithiols and gold nanoparticles were prepared, and the photochemical reactivity and photoswitching of the conductance were studied. The networks showed a completely reversible photoswitching of the conductance according to the photochromic reactions of the diarylethene units. The switching behavior is attributed to the change of the π-conjugation length of the molecule. Because of the high switching ratio and good reversibility this switching system opens up the possibility of sophisticated molecular electric circuits.
Co-reporter:Soichi Yokoyama, Takashi Hirose and Kenji Matsuda
Chemical Communications 2014 - vol. 50(Issue 45) pp:NaN5966-5966
Publication Date(Web):2014/01/16
DOI:10.1039/C3CC48895K
A photoresponsive self-assembly on a 2-D surface was investigated by scanning tunnelling microscopy (STM). The open-ring isomer of a diarylethene derivative showed an abrupt ordering formation at a critical concentration, which was successfully reproduced by a cooperative model based on Langmuir-type adsorption.
Co-reporter:Takeshi Sakano, Kenji Higashiguchi and Kenji Matsuda
Chemical Communications 2011 - vol. 47(Issue 29) pp:NaN8429-8429
Publication Date(Web):2011/06/24
DOI:10.1039/C1CC12041G
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.
Co-reporter:Takashi Hirose and Kenji Matsuda
Chemical Communications 2009(Issue 39) pp:NaN5834-5834
Publication Date(Web):2009/09/08
DOI:10.1039/B910531J
A 1-cyano-1,2-bis(biphenyl)ethene derivative having hexa(ethylene glycol) groups as amphiphilic side chains showed aggregate-induced enhanced emission in water; upon heating the intensity of the enhanced emission was attenuated in a lower temperature range than the temperature range where exciton interaction is still effective.
Co-reporter:Takashi Hirose, Natsuki Ito, Hiromu Kubo, Tohru Sato and Kenji Matsuda
Journal of Materials Chemistry A 2016 - vol. 4(Issue 14) pp:NaN2819-2819
Publication Date(Web):2016/01/26
DOI:10.1039/C5TC03675E
The surrounding environment of a molecular fluorophore is one of the most important determining factors in luminescence properties, such as the emission quantum yield, the lifetime of the excited state, and the color of luminescence. In this work, we investigate the relationship between the self-assembled structure and the fluorescence properties of [5]helicene derivatives in the solution phase. A [5]Helicene derivative bearing the tri(ethylene glycol) group formed spherical aggregates in aqueous media and that bearing the (3,4,5-trioctyloxyphenyl)carbamoyl group formed fibrous aggregates in apolar solvent. Analysis based on the radiative (kf) and non-radiative (knr) rate constants suggests that (1) an aggregation-induced suppression of fluorescence observed in aqueous media is attributed to the decrease of kf, (2) an aggregation-induced enhancement of fluorescence observed for fibrous aggregates formed in an apolar solvent is associated with the suppression of knr, (3) [5]helicenes become almost non-fluorescent especially in a polar solvent by introducing an appropriate donor substituent due to a charge-transfer (CT) type property in the lowest energy excited state, and (4) the strong quenching effect due to the CT-type excitation can be efficiently alleviated by several approaches, such as by forming aggregates with an appropriate self-assembly motif or by controlling the energy level of molecular orbitals.
Co-reporter:Takashi Hirose and Kenji Matsuda
Organic & Biomolecular Chemistry 2013 - vol. 11(Issue 6) pp:NaN880-880
Publication Date(Web):2012/11/29
DOI:10.1039/C2OB27049H
Photochromic diarylethene is a promising candidate not only for optical memory and switching units in molecular devices, but also as a photoresponsive building block that can regulate supramolecular architectures because of its characteristic changes in the flexibility of the framework and delocalization of π-electrons, along with its photoisomerization ability. Amphiphilic photochromic compounds with oligo-(ethylene glycol) side chains show good solubility in water, and self-assemble into nanostructures in aqueous media. Asymmetric introduction of a methyl group can induce a helical preference in the supramolecular structure, and the photoswitching behaviour of supramolecular chirality was defined by circular dichroism (CD) spectroscopy and density functional theory (DFT) calculations. The effective position of an asymmetric group to induce supramolecular chirality is also discussed. In addition, the self-assemblies of diarylethene derivatives in water show photoresponsive lowest critical solution temperature (LCST). The open- and closed-ring isomers show LCST transitions at different temperatures. In particular, the difference in LCST becomes prominent when amide groups are introduced at the root of hydrophilic side chains. This is attributed to intermolecular hydrogen bonds formed by the amide groups in the hydrophobic region of the supramolecular structure in water.
