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• Chemistry of curved aromatic compounds

  Chemistry of curved aromatic compounds

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  Aromatic compounds, such as benzene, exhibit their unique reactivity and physical properties by "aromaticity", in which pi-electrons are widely distributed in the planar molecular skeleton. Therefore, the planarity of the molecule is one of the important aspects to deliver the property of these aromatic molecules. What would happen if the aromatic molecules possess curved, bent, or any non-planer structures in their reactivity as well as the physical properties? From such a simple curiosity, we investigate the chemistry of spherical aromatic compounds "fullerenes" and bowl-shaped compounds "buckybowls". In particular, the buckybowl not only exhibits various unique behaviors due to its unique bowl structure, but also are expected to be unique materials having new functions, which cannot be realized with planar aromatic compounds.
  We succeeded in the first synthesis of "sumanene", one of the pristine structures of buckybowls. Currently we study on new synthetic methods and properties of various buckybowls, and the development of functional materials using buckybowls. Here listed the examples of recent research.

  • ・Construction of novel structures and supramolecular structures having sumanene as a motif and their physical properties
  • · New synthetic methods to construct buckybowl frameworks, particularly heterobuckybowls
  • · Novel materials utilizing the intrinsic two-sidedness (Janus nature) caused by concave surface and convex surface of buckybowl
  • · Preparation of metal colloids protected by water-soluble fullerene derivatives and their application to catalysts and materials

  

  

• Chemistry of metal nanoclusters

  Chemistry of metal nanoclusters

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  The character of metals is totally different when the size of the metal decreases from the bulk state to the nanometer size (clusters). For example, "gold" is one of the most corrosive (air oxidation) resistant metals that eternally shine in bulk, but nanometer size gold shows extremely high catalytic activity toward aerobic oxidation. In this way, various unknown catalytic activities and physical properties, hidden in bulk state, will exist in metal nanoclusters.
  Furthermore, in the nanocluster state, it is possible to make alloy cluster state by mixing multiple metals in various combinations and ratios. Such alloy clusters may exhibit totally different activity from the original single metal. We can say that we do something like modern "alchemy".
  Since these metal nanoclusters tend to agglomerate to be buck to bulk, it is necessary to stabilize them with a protective agent. We found that even the type of protective matrix can greatly change the nature of the cluster. We now study the development of novel metal nanocluster catalysts contributable to green chemistry, using various synthetic and natural polymers as protective agents. Here listed the examples of recent research.

  • · Development of novel catalytic reaction using alloy nanocluster catalyst, in particular to pursue challenging reactions such as carbon-fluorine bond activation
  • · Development of a practical green nanocatalyst using various synthetic and/or natural polymers such as chitosan and cellulose as a protective matrix.
  • · Elucidation of phenomena and interaction at the interface between metal nanocluster surface and protective matrix in catalytic reaction

  

  

• Dynamics of organic crystals

  Dynamics of organic crystals

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  Crystal is a substance in which atoms, molecules and ions are regularly arranged spatially, and rock salt, quartz, jewels such as ruby and sapphire are also types of crystals. Even in the case of larger organic compounds as constituents, in the crystalline state they are arrayed with spatially repeated patterns. Because these organic crystals are very rigid, they are advantageous for manifesting physical properties, but on the contrary they are fragile because of lack of flexibility, and most of them will collapse as soon as pressure is applied. However, recently, "dynamic" organic crystals that can flexibly change the structure against external stimulus are attracting attention. For example, a system that responds to pressure and changes the color of emitted light has also been reported.
  Recently, we have found a series of dynamic organic crystals that reversibly shows dynamic structural change while maintaining crystalline state as guest molecules like solvents ingest / release. Also, some of these crystals were reversibly changed color and structure by heating or light irradiation. These organic crystals are composed only of very simple organic compounds and furthermore it is expected that further modifications can be added without changing the basic dynamic properties by subjecting these compounds to chemical modification It has been. A concrete example of recent research is as follows.

  • ・Elucidation of porosity / non-porous structural change in dynamic organic crystals accompanying uptake / release of solvent
  • · Elucidation of structure transition phenomenon by heating and light irradiation indicated by dynamic organic crystal, material development utilizing it
  • · Control of molecular uptake characteristics by chemical modification of constituent molecules

  

  

• Chemistry of laser ablation

  Chemistry of laser ablation

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  By irradiating laser light to the interface between solid and liquid, constituent substances on the solid surface are explosively released as plasma is generated (ablation). This allows extremely active chemical species to be generated in the liquid. We are trying to apply this method to various research based on organic chemistry and complex chemistry.
  For example, in the global environment of 4.3 billion years ago, we use it to elucidate the mechanism by which the first primitive enzyme-like substance that holds the key to life evolution is formed. That is, laser ablation was regarded as a part of the ionizing radiation effect by the natural nuclear reactor that existed at the time, ablation in pure pyrite (FeS₂) which existed at the time of the surface at the time in the presence of simple organic compound By doing so, we generate primitive enzyme model complexes and evaluate these reactivities.
  Besides that, active nano particles are generated by laser ablation of metals and solid compounds, and we are studying catalytic reaction etc. using it. A concrete example of recent research is as follows.

  • · Study on elucidation of primitive enzyme-like substance generation mechanism in the Hidari dynasty
  • · Development of size / morphology selective nanoparticle formation method by liquid phase laser ablation on metal and solid compound surface
  • · Generation of new alloys using laser bonding technology and its reactivity evaluation