Spectroscopic and electrical characterization of α,γ-bisdiphenylene-β-phenylallyl radical as an organic semiconductor


The semiconductor properties of the earliest known stable radical, α,γ-bisdiphenylene-β-phenylallyl radical (Koelsch radical, 1) were assessed using spectroscopic and electrical techniques. This radical undergoes reversible redox processes, and it has low redox potentials. In addition, 1 possesses long wavelength absorption bands, owing to the existence of a singly-occupied molecular orbital whose energy level lies between those of the HOMO and LUMO. A spin-coated thin-film of 1 displays photocurrent and an electron mobility of 6.3 × 10−7 cm2 V−1 s−1 on a trially-fabricated organic field effect transistor.

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    For the details, see the Supplementary Material.

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    The BDPA radical has been commercially available from Aldrich since February 2015. See: www.sigmaaldrich.com/catalog/product/aldrich/152560.


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The authors acknowledge valuable discussions with Mr. Yu Suenaga at OPU. This study was partially supported by JSPS KAKENHI grant numbers JP24109009 (Innovative Area Stimuli-responsive Chemical Species), JP17H01265, JP23350023, JP23108718 (pi-Space), JP21108520, JP21655016, and JP19350025. YM also acknowledges the Program to Disseminate Tenure Tracking System, MEXT, Japan.

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Correspondence to Hiroshi Ikeda.

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Matsui, Y., Shigemori, M., Endo, T. et al. Spectroscopic and electrical characterization of α,γ-bisdiphenylene-β-phenylallyl radical as an organic semiconductor. Res Chem Intermed 44, 4765–4774 (2018). https://doi.org/10.1007/s11164-018-3282-7

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  • Stable radical
  • Koelsch radical
  • BDPA radical
  • Organic field effect transistor
  • Organic semiconductor