Masanori Shigeno

Tohoku University, Miyagi, Japan

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Publications (16)89.89 Total impact

  • Masanori Shigeno · Tsukasa Sawato · Masahiko Yamaguchi ·
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    ABSTRACT: Oxymethylenehelicene (P)- and (M)-oligomers up to a nonamer were synthesized by a building block method. The oligomers formed dimeric homoaggregates in trifluoromethylbenzene. A mixture of the pseudoenantiomeric (P)-pentamer and (M)-hexamer formed a heteroaggregate, which self-assembled into one-dimensional fibril films at the liquid-solid interface. Discontinuous heterogeneous nucleation occurred, which involved the formation of particles that were 50 nm in diameter and subsequent fibril growth from these particles. The fibril film was formed on the solid surface and the molecules remained dissociated in solution. The fibril film formation was affected by seeding and the solid surface materials.
    Chemistry - A European Journal 10/2015; DOI:10.1002/chem.201503224 · 5.73 Impact Factor
  • Yo Kushida · Masanori Shigeno · Masahiko Yamaguchi ·
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    ABSTRACT: Sulfonamidohelicene tetramer (M)-1 exhibits a concentration threshold and amplification phenomena in solution during helix-dimer formation from a random-coil. The (M)-tetramer is a random-coil below a threshold concentration, and the concentration of the helix-dimer is irreversibly amplified once the threshold concentration is exceeded. For example, a 15 % increase in (M)-tetramer total concentration from 0.6 to 0.7 mM induces an 8-fold increase in the concentration of the helix-dimer, being 8:0.15=53-fold amplification, under temperature oscillation conditions between 47 and 49 °C. Experiments without oscillation also exhibit concentration amplification. The threshold and amplification phenomenon involves concentration hysteresis, being away from equilibrium, and self-catalysis. On the basis of this study, a proposal on how a biological cell senses concentration changes of a chemical substance is provided. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - A European Journal 08/2015; 21(39). DOI:10.1002/chem.201501474 · 5.73 Impact Factor
  • Masanori Shigeno · Yo Kushida · Masahiko Yamaguchi ·
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    ABSTRACT: Molecular switching is a phenomenon by which a molecule reversibly changes its structure and state in response to external stimuli or energy. Herein, molecular switching is discussed from thermodynamic and kinetic aspects in terms of energy supply with an emphasis on the thermal switching exhibited by helicene oligomers. It includes the inversion of relative thermodynamic stability induced by temperature changes and molecular thermal hysteresis in a closed system. The thermal phenomenon associated with the oligomers involves population/concentration changes between metastable states under nonequilibrium thermodynamic control. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    ChemPhysChem 05/2015; 16(10). DOI:10.1002/cphc.201500210 · 3.42 Impact Factor
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    Masanori Shigeno · Yo Kushida · Masahiko Yamaguchi ·
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    ABSTRACT: The sulfonamidohelicene tetramer changes its structure between a random-coil and a helix-dimer, by which molecular thermal hysteresis appears. Mixing experiments on helix-dimer and random-coil solutions and kinetic analysis show that the transition from the random-coil to the helix-dimer involves self-catalysis by the helix-dimer.
    Chemical Communications 02/2015; 51(19). DOI:10.1039/c4cc10418h · 6.83 Impact Factor
  • Masamichi Miyagawa · Atsushi Yagi · Masanori Shigeno · Masahiko Yamaguchi ·
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    ABSTRACT: When a toluene solution of ethynylhelicene (M)-nonamer is cooled and heated between 95 and 5 °C at a constant rate, molecular thermal hysteresis. i.e., different courses of the structure change between a double-helix and a random-coil, occurs. Note that the structure change from the random-coil to the double-helix during heating crosses equilibrium and results in excessive concentrations of the double-helix. This phenomenon is named equilibrium crossing. Our experiment revealed an accelerated rate of formation of the double-helix from the random-coil while moving away from equilibrium. The acceleration of the reaction was also observed in constant-temperature experiments at 20 and 25 °C, where the reactions are faster at the intermediate states than at the initial states. A mechanistic model is provided, which involves self-catalysis and a temperature-dependent shift of equilibrium.
    Chemical Communications 09/2014; 50(92). DOI:10.1039/C4CC06955B · 6.83 Impact Factor
  • Masanori Shigeno · Yo Kushida · Yuta Kobayashi · Masahiko Yamaguchi ·
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    ABSTRACT: The sulfoneamidohelicene tetramer in solution exhibits different molecular responses to the same cooling stimulus delivered once and twice under thermal hysteresis conditions. Its random-coil state at a high temperature was cooled and maintained at a given temperature for which its molecules remained in a random coil (first cooling); the resulting solution was heated and cooled, after which a helix dimer formed (second cooling). Such a property can be regarded as a molecular function of counting the numbers 1 and 2.
    Chemistry - A European Journal 09/2014; 20(40). DOI:10.1002/chem.201403358 · 5.73 Impact Factor
  • Masanori Shigeno · Masahiko Sato · Yo Kushida · Masahiko Yamaguchi ·
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    ABSTRACT: Aminomethylenehelicene oligomers up to the (M)-heptamer were synthesized by reductive amination from a formylhelicene building block. The oligomers containing more than three helicenes formed a double helix in 1,3-dilfuorobenzene. The (M)-tetramer and (M)-pentamer unfolded into a random coil by heating to 60 °C, whereas the (M)-hexamer only slightly unfolded at the same temperature. A two-sided thermal hysteresis was detected in the structural change of the (M)-tetramer and (M)-pentamer during cooling and heating. The (M)-pentamer and (M)-hexamer unfolded with the addition of trifluoroacetic acid and regenerated a double helix with the addition of triethylamine.
    Asian Journal of Organic Chemistry 07/2014; 3(7). DOI:10.1002/ajoc.201402065 · 3.32 Impact Factor
  • Masahiko Yamaguchi · Masanori Shigeno · Nozomi Saito · Koji Yamamoto ·
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    ABSTRACT: Polycyclic aromatic compounds are an important group of substances in chemistry, and the study of their properties is a subject of interest in the development of drugs and materials. We have been conducting studies to develop chiral polycyclic aromatic compounds, i.e., helicenes and equatorenes. These helical molecules showed notable aggregate-forming properties and the capability for chiral recognition exerted by noncovalent bond interactions, which were not observed in compounds with central chirality. Homo- and hetero-double-helix-forming helicene oligomers were developed, and the latter self-assembled to form gels and vesicles. In this article, we describe such hierarchical studies of polycyclic aromatic compounds, which were started from polyketide aldol synthesis.
    The Chemical Record 05/2014; 45(20). DOI:10.1002/tcr.201300014 · 5.49 Impact Factor
  • Masanori Shigeno · Yo Kushida · Masahiko Yamaguchi ·
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    ABSTRACT: A 1:1 mixture of pseudoenantiomeric aminomethylenehelicene (P)-tetramer and (M)-pentamer formed three states, namely, the hetero-double helices B and C and the random coil A. At high temperatures, A is the most stable. At low temperatures, C is the most stable, and the structural changes from A to the metastable state B to the product C occur, where B and C have enantiomeric helical structures. Heating then converts C to A. Essentially all the molecules change their structure in a one-direction manner from A to B to C to A. Various nonequilibrium reversible thermodynamic responses appeared depending on thermal conditions: The metastable states A and B can be interconverted with thermal hysteresis without forming C in a far-from-equilibrium manner; they can be frozen at low temperatures and defrosted by warming; three-state hysteresis occurs. An energy and population model for nonequilibrium thermodynamic phenomena is given, involving two metastable states and thermal hysteresis.
    Journal of the American Chemical Society 05/2014; 136(22). DOI:10.1021/ja502009f · 12.11 Impact Factor
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    ABSTRACT: Metal/semiconductor interfaces govern the operation of semiconductor devices through the formation of charge injection barriers that can be controlled by tuning the metal work function. However, the controlling ability is typically limited to being static. We show that a dynamic nature can be imparted to the interfaces using electrode surface modification with a structurally disordered molecular monolayer. The barrier height at the interfaces is altered significantly in a reversible way by an external electric field. As a result, a dramatic change in the carrier transport properties through the interfaces is observed, such as a reversible polarity reversion of metal/organic-semiconductor/metal diodes.
    Applied Physics Letters 01/2014; 104(1). DOI:10.1063/1.4861164 · 3.30 Impact Factor
  • Masanori Shigeno · Yo Kushida · Masahiko Yamaguchi ·
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    ABSTRACT: Sulfonamidohelicene oligomers up to the nonamer level were synthesized by the repeated coupling reactions of a building block. A tetramer formed a helix dimer in 1,3-difluorobenzene, which unfolded to a random coil with heating. This structural change exhibited thermal hysteresis in which different thermal responses were observed in the course of temperature increase and decrease. The feature of the hysteresis was examined under different heating/cooling modes, and the mechanisms are discussed on the basis of the population change and the presence of an induction period. A proposal regarding the use of thermal hysteresis for sensing a temperature increase/decrease is also given.
    Chemistry - A European Journal 07/2013; 19(31). DOI:10.1002/chem.201204556 · 5.73 Impact Factor
  • Wataru Ichinose · Masanori Shigeno · Masahiko Yamaguchi ·
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    ABSTRACT: An (amido-ethynyl)helicene bidomain compound and an (amido-ethynyl-amido)helicene tridomain compound were synthesized. The multidomain compounds were designed on the basis of previous findings that amido and ethynyl oligomers form dimeric aggregates with properties orthogonal to each other. Four aggregate states of multidomain compounds, namely, all-dimer, amido-dimer, ethynyl-dimer, and random-coil states, were obtained in different solvents, which were analyzed by circular dichroism (CD), UV/Vis, (1) H NMR, and IR spectroscopy; vapor pressure osmometry (VPO); dynamic light scattering (DLS); and atomic force microscopy (AFM). The amido and ethynyl domains independently aggregated and disaggregated in a two-state manner. Reversible structural changes occurred for a tridomain compound between the ethynyl-dimer/random-coil state and the all-dimer/amido-dimer state with heating and cooling. Two structural change processes with different properties were obtained using a single compound.
    Chemistry - A European Journal 10/2012; 18(40):12644-54. DOI:10.1002/chem.201201929 · 5.73 Impact Factor
  • Nozomi Saito · Masanori Shigeno · Masahiko Yamaguchi ·
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    ABSTRACT: A methodology for the formation of fibers/gels and vesicles by molecular assembly and for controlling their properties is presented. Two-component systems of pentamer (P)-5 and tetramer (M)-4 pseudoenantiomeric ethynylhelicenes with decyloxycarbonyl (D) and 4-methyl-2-(2-methylpropyl)-1-pentyloxycarbonyl (bD) side-chains have been examined. Distinct aggregates were formed by changing the solvent for the three combinations of (P)-bD-5/(M)-bD-4, (P)-D-5/(M)-bD-4, and (P)-D-5/(M)-D-4. In toluene, (P)-bD-5/(M)-bD-4, (P)-D-5/(M)-bD-4, and (P)-D-5/(M)-D-4 all formed gels and fibrous assemblies were observed by AFM. The minimum gel-forming concentration (MGC) decreased in the order (P)-bD-5/(M)-bD-4>(P)-D-5/(M)-bD-4>(P)-D-5/(M)-D-4. In diethyl ether, vesicular formation was observed by dynamic light scattering (DLS), AFM, and TEM, and the size of the vesicles decreased in the order (P)-bD-5/(M)-bD-4>(P)-D-5/(M)-bD-4>(P)-D-5/(M)-D-4. Both fiber/gel and vesicle formation were accompanied by enhanced CDs and redshifted UV/Vis absorption bands with a change in color to deep yellow. These are novel two-component oligomeric systems that form assemblies of fibers/gels or vesicles depending on the solvent, and the structures and properties of the assemblies can be fine-tuned by changing the combination of oligomers. In m-difluorobenzene, a homogeneous solution was obtained with (P)-D-5/(M)-bD-4, which again exhibits enhanced CDs and redshifted UV/Vis absorptions. Vapor pressure osmometry analysis showed the formation of a bimolecular heteroaggregate. The study has indicated that pseudoenantiomeric oligomers form hetero-double-helices that hierarchically assemble to form fibers/gels and vesicles.
    Chemistry - A European Journal 07/2012; 18(29):8994-9004. DOI:10.1002/chem.201200280 · 5.73 Impact Factor
  • Masanori Shigeno · Masahiko Yamaguchi ·
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    ABSTRACT: Organic gel-liquid two-layer systems were constructed by two-liquid-ultrasonication-diffusion-controlled gelation using the chiral aminohydroxyhelicene derivative (M)-1. Gelation took place by the diffusion of (M)-1 and THF from the bottom layer to the upper hexane layer. This method provided multilayer liquid-gel systems.
    Chemical Communications 05/2012; 48(49):6139-41. DOI:10.1039/c2cc31977b · 6.83 Impact Factor
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    ABSTRACT: The reverse amidohelicene (P)-tetramer containing (P)-helicenediamine and m-phenylenedicarboxylate was synthesized. The circular dichroism (CD) and vapor pressure osmometry (VPO) analysis revealed the dimeric aggregate formation in THF. It is notable that the reverse amide tetramer formed a duplex, as well as the original amidohelicene oligomers. In various solutions, mixtures of the reverse (P)-tetramer and amidohelicene (P)/(M)-tetramer formed homoaggregates instead of heteroaggregates.
    Tetrahedron 07/2011; 67(30):5477-5486. DOI:10.1016/j.tet.2011.05.059 · 2.64 Impact Factor
  • Nozomi Saito · Ryo Terakawa · Masanori Shigeno · Ryo Amemiya · Masahiko Yamaguchi ·
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    ABSTRACT: Three series of ethynylhelicene oligomers with different side chains were synthesized: (P)-bD-n (n = 2-6) with branched alkyloxycarbonyl side chains; (P)-S-n (n = 2-7) with decylsulfanyl side chains; and (P)-DF-n (n = 4, 6, 8, 10) with alternating decyloxycarbonyl and perfluorooctyl side chains. The double helix formation of these side chain derivatives was compared to that of (P)-D-n with decyloxycarbonyl side chains. CD, UV-vis, and vapor pressure osmometry (VPO) studies showed that (P)-bD-n formed double helices as well as (P)-D-n. CD studies in trifluoromethylbenzene at different temperatures and concentrations indicated that the stability of the aggregate of (P)-bD-6 was similar to that of (P)-D-6. Bulkiness of side chains had little effect on aggregation, which indicated that π-π interactions of the aromatic moiety were essential for double helix formation. (P)-S-n were random coils in all solvents examined except in trifluoromethylbenzene. Whereas (P)-D-7 formed a double helix at 1 × 10(-3) M in toluene, (P)-S-7 was a random coil. This result indicated that the double helix forming ability of (P)-S-n was substantially lower than that of (P)-D-n. Based on the previous observation that (P)-F-n formed a more stable double helix than (P)-D-n, the order of stability may be summarized as follows: (P)-F-n > (P)-D-n and (P)-bD-n >(P)-S-n. The lower stability of (P)-S-n compared to that of (P)-F-n was ascribed to the softness and/or the electron-rich nature at the m-phenylene moiety. (P)-DF-n did not form a stable double helix. It was speculated that a regular alternating arrangement of soft/hard or electron-rich/deficient moieties is important for stable double helix formation. Side chains of ethynylhelicene oligomers can play significant roles in determining the stability of double helices.
    The Journal of Organic Chemistry 06/2011; 76(12):4841-58. DOI:10.1021/jo200658q · 4.72 Impact Factor