Toshikazu Ono

Graduate School of Engineering, Kyushu University
Associate professor

Participating Group (2020-2021)

Planned creation and development of organic metastable crystals using salt-cocrystal continuum phase

Salt–cocrystal Continuum, Multicomponent Crystal, Phase Transition, Soft Crystal

Research Outline

The regulation of proton transfer dynamics between acid–base complexes is of significant interest in the pharmaceutical industry and materials chemistry. It is generally accepted that ⊿pKa values (pKa (protonated base) – pKa (acid)) and the crystalline environment determine the extent of proton transfer, which is recognized as a ⊿pKa rule. When the pKa value is greater than 4, a salt is expected to form (all components are charged), and a pKa value below -1 leads toward cocrystals forming (all components in their neutral states). However, when ⊿pKa is in the range of -1 < ⊿pKa < 4, the crystals exist as a molecular salt, a cocrystal, or a disordered solid with partial proton transfer forms, and the location of the acidic proton is dependent on the specific crystal packing environment. In this study, we focus on the fact that the salt-cocrystal continuum is a metastable crystals, and realize the systematic creation of “multi-component soft crystals” that show changes in optical properties in response to various external stimuli.

Planned Creation and Development of Organic Metastable Crystals
Emission Color Changes of Salt–Cocrystal Continuum depends of Degree of Protonation


Academic papers/reviewed


  1. " Hydrogen Bond Engineering Visualized by Picometer-Level Distortion of Planar Porphyrin Isomers " D. Koga, *T. Ono, H. Shinjo, *Y. Hisaeda, J. Phys. Chem. Lett., 12, 10429-10436 (2021).
  2. " Insights into Proton Dynamics in Photofunctional Salt–cocrystal Continuum: Single-crystal X-ray, Neutron Diffraction, and Hirshfeld Atom Refinement " Y. Yano, *T. Ono, T. Ohhara, *Y. Hisaeda, Chem. Eur. J., 27, 17802-17807 (2021).
  3. "Room-temperature phosphorescence emitters exhibiting red to near-infrared emission derived from intermolecular charge-transfer triplet states of naphthalenediimide-halobenzoate triad molecules " T. Ono, K. Kimura, M. Ihara, Y. Yamanaka, M. Sasaki, H. Mori, *Y. Hisaeda, Chem. Eur. J., 27, 9535-9541 (2021).
  4. Highly Fluorescent Bipyrrole-Based Tetra-BF2 Flag-Hinge Chromophores: Achieving Multicolor and Circularly Polarized Luminescence, Luxia Cui, Hyuga Shinjo, Takafumi Ichiki, Koichi Deyama, Takunori Harada, Kohei Ishibashi, Takumi Ehara, Kiyoshi Miyata, Ken Onda, Yoshio Hisaeda, Toshikazu Ono,Angew. Chem. Int. Ed. 2022, e202204358(領域内共同研究A03恩田)リョウイキナイ
  5. "Vapochromism of Organic Crystals based on Macrocyclic Compounds and Inclusion Complexes" *T. Ono, *Y. Hisaeda, Symmetry, 12, 1903 (2020).
  6. "Dinuclear Triple-Stranded Helicates Composed of Tetradentate Ligands with Al(III) Chromophores: Optical Resolution and Multi-Color Circularly Polarized Luminescence Properties" *T. Ono, K. Ishihama, A. Taema, T. Harada, K. Furusho, Y. Nojima, M. Hasegawa, M. Abe, *Y. Hisaeda, Angew. Chem. Int. Ed., 60, 2614-2618 (2021).
  7. "Dinuclear Triple-stranded Helicates Comprising Al(III), Ga(III), or In(III) and a Hydrazine-linked Bisiminopyrrolyl Ligand: Synthesis, Structure, Optical Resolution, and Chiroptical Properties" K. Ishihama, *T. Ono, T. Okawara, T. Harada, K. Furusho, Y. Nojima, M. Hasegawa, M. Abe, *Y. Hisaeda, Bull. Chem. Soc. Jpn., 94, 573-578 (2021).

Media, Outreach activity, Patent, others


  • Multicomponent Crystals with Competing Intermolecular Interactions: In Situ X-ray Diffraction and Luminescent Features Reveal Multimolecular Assembly of Mechanochemical Conditions
    Yoshio Yano,Hidetaka Kasai,Yanyan Zheng,Eiji Nishibori,Yoshio Hisaeda,Toshikazu Ono
    Angew. Chem. Int. Ed. 2022, e202203853. (領域内共同研究A02公募西堀)キョウドウケンkニュウ