RESEARCH

Many of the materials that are useful in our lives are "solids." In our group, we design and synthesize functional molecules using various elements and create "crystals," which have a beautifully arranged molecules in solid. These molecular crystals can serve as a great platform to investigate the novel functions with the mechanism by taking advantage of structural information in molecular level. Normally, the atoms or molecules inside a crystal are fixed due to the densely packed environment, but we are researching the design of crystalline materials where molecules inside the crystal can move (rotating, shifting, etc) in response to external stimuli or environmental changes. The movement of a single molecule is on a microscopic scale, so the effects derived from molecular motion are small. However, when many molecules are aligned in a crystal and cause molecular movement, the effects resulting from this movement are dramatically integrated, allowing the functionality to be expressed on a scale we can physically handle. How molecules are "arranged" and "moved" within a crystal is still an unexplored area in chemistry, as it is less advanced compared to the research in molecular synthesis.

  • RESEARCH

    Design of crystalline molecular rotors via N-heterocyclic carbene (NHC) oranometallic complexes

    Organometallic complexes constructed from organic molecules and metals can create a diverse range of molecular structures and electronic environments. We have developed a new crystalline molecular rotor that allows for semi-rational control of molecular rotation within the crystal, based on metal complexes with N-heterocyclic carbene (NHC) ligands. Additionally, the luminescent properties exhibited by these crystals can be controlled by molecular rotation (as seen in the top left figure). More recently, through creating bulky structures with NHC compounds, we have succeeded in rotating the largest size of molecule within a crystal, demonstrating rotational motion in a solid state (as seen in the top right figure).

  • RESEARCH

    Crystalline molecular gears: Designing correlated (geared) molecular motions in crystalline solid.

    Gears are mechanical components essential for the transmission and regulation of power at the macroscopic scale. In the nanoscale, proteins working in concert within cells perform gear-like motions and fulfill their functions. Inspired by the bio-system, there is a robust interest in research to mimic gear movements at the nanoscale using synthetic molecules. However, most of "molecular gears" have been studied in solution, where molecules can easily move and rotate. In contrast, studies of molecular-level gear motion within solid-state are exceedingly rare. This is due to the high difficulty associated with the dense packing of molecules in crystals, which restricts their rotation compared to in solution.

    Very recently, we have succeeded to develop a molecular rotor incorporating three phenylene rotating units attached to a triazine core, with bulky stators at the side position (as seen in the top left figure). By crystallizing the molecule, we have formed an intermolecular clutch stacking structure within the solid state, allowing for the adjacent phenyl groups to engage in concerted rotational movements (gear motion) within the crystal (as depicted in the top figure). The versatility of this design concept allows for the introduction of various molecular blocks at the terminal structures and rotating units, paving the way for the creation of diverse functionalized crystalline molecular gear structures in the future.

Research papers & reviews

  1. 1.

    A Steric-Repulsion-Driven Clutch Stack of Triaryltriazines: Correlated Molecular Rotations and a Thermo-Responsive Gearshift in the Crystalline Solid

    Jin, M.*; Kitsu, R.; Hammyo, M.; Sato-Tomita, A.; Mizuno, M.; Mikherdov, A.S.; Tsitsvero, M.; Lyalin, A.; Taketsugu, T.; Ito, H.*

    J. Am. Chem. Soc. 2023, 145, 27512–27520.

    DOI: 10.1021/jacs.3c08909

  2. 2.

    Giant Crystalline Molecular Rotors that Operate in the Solid State

    Ando, R.; Sato-Tomita, A.; Ito, H.*; Jin, M.*

    Angew. Chem. Int., Ed. 2023, 62, e202309694.

    DOI: 10.1002/anie.202309694

  3. 3.

    Encapsulating N-Heterocyclic Carbene Binuclear Transition-Metal Complexes as a New Platform for Molecular Rotation in Crystalline Solid-State

    Jin, M.*; Ando, R.; Jellen, M.J.; Garcia-Garibay, M.A.; Ito, H.*

    J. Am. Chem. Soc. 2021, 143, 1144–1153.

    DOI: 10.1021/jacs.0c11981

  4. 4.

    Solid-State Luminescence of Au(I) Complexes with External Stimuli-Responsive Properties

    Jin, M.* and Ito, H.*

    J. Photochem. Photobio. C: Photochem. 2022, 51, 100478. (Review paper)

    DOI: 10.1016/j.jphotochemrev.2021.100478

Press release

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