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Graduate University

Group Detail

Department of Functional Molecular Science

Kusamoto Group


Research Theme

Creation of novel photonic-electronic-magnetic functions based on molecules with open-shell electronic structures


Radical, Open-shell electronic states, Photonic-electronic-magnetic properties

The molecules with open-shell electronic states can exhibit unique properties, which are difficult to achieve for conventional closed-shell molecules. Our group develops new open-shell organic molecules (= radicals) and metal complexes to create novel photonic-electronic-magnetic functions.

While conventional closed-shell luminescent molecules have been extensively studied as promising components for organic light-emitting devices, the luminescent properties of radicals have been much less studied because of its rarity and low chemical (photo-)stability. We have developed a novel luminescent organic radical PyBTM, which is highly stable at ambient condition and in the photoexcited state. We have also discovered that (i) PyBTM-doped molecular crystals exhibit photoluminescence with a room-temperature emission quantum yield of 89%, which is exceptionally high in radicals, and (ii) the doped crystals show drastic changes in the emission spectra by applying a magnetic field. This is the first observation of the magnetoluminescence in organic radicals. Our studies provide novel and unique insights in molecular photonics, electronics, and spintronics, and also contribute to developing applied science for light-emitting devices.

Our group focuses on frustrated spins in molecular crystals. The anisotropic assembly of open-shell molecules in crystalline states can afford unusual electronic states attributed to the frustrated spins, providing exotic electrical and magnetic properties.


(a) Molecular structure of PyBTM and its characteristics.
(b) Schematic photoexcitation-emission processes.
(c) Emission in CH2Cl2.
(d) Emission of PyBTM-doped molecular crystals.
(e) Controlling emission by magnetic field.

Selected Publications

  1. S. Kimura, S. Kimura, K. Kato, Y. Teki, H. Nishihara, and T. Kusamoto "A ground-state-dominated magnetic field effect on the luminescence of stable organic radicals" Chem. Sci. 12, 2025-2029 (2021).
  2. S. Kimura, T. Kusamoto, S. Kimura, K. Kato, Y. Teki, and H. Nishihara ‘‘Magnetoluminescence in a Photostable, Brightly Luminescent Organic Radical in a Rigid Environment’’ Angew. Chem. Int. Ed. 57, 12711–12715 (2018).
  3. Y. Hattori, T. Kusamoto, and H. Nishihara ‘‘Luminescence, Stability, and Proton Response of an Open-Shell (3,5-Dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl Radical’’ Angew. Chem. Int. Ed53, 11845–11848 (2014).
  4. T. Kusamoto, H. M. Yamamoto, N. Tajima, Y. Oshima, S. Yamashita, and R. Kato ‘‘Bilayer Mott System with Cation···Anion Supramolecular Interactions Based on Nickel Dithiolene Anion Radical: Coexistence of Ferro- and Antiferro-magnetic Anion Layers and Large Negative Magnetoresistance’’ Inorg. Chem. 52, 4759−4761 (2013).

Lab Staff