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Updated: Nov 1, 2025

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Published on: April 24, 2014
A ground-state-dominated magnetic field effect on the luminescence of stable organic radicals
Shun Kimura1,2, Shojiro Kimura3, Ken Kato4
1Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science 5-1 Higashiyama, Myodaiji Okazaki Aichi 444-8787 Japan kusamoto@ims.ac.jp.
Abstract:
Organic radicals are an emerging class of luminophores possessing multiplet spin states and potentially showing spin-luminescence correlated properties. We investigated the mechanism of recently reported magnetic field sensitivity in the emission of a photostable luminescent radical, (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM) doped into host αH-PyBTM molecular crystals. The magnetic field (0-14 T), temperature (4.2-20 K), and the doping concentration (0.1, 4, 10, and 22 wt%) dependence on the time-resolved emission were examined by measuring emission decays of the monomer and excimer. Quantum mechanical simulations on the decay curves disclosed the role of the magnetic field; it dominantly affects the spin sublevel population of radical dimers in the ground states. This situation is distinctly different from that in conventional closed-shell luminophores, where the magnetic field modulates their excited-state spin multiplicity. Namely, the spin degree of freedom of ground-state open-shell molecules is a new key for achieving magnetic-field-controlled molecular photofunctions.
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