Acta Chimica Sinica ›› 2022, Vol. 80 ›› Issue (2): 101-104.DOI: 10.6023/A21120564 Previous Articles     Next Articles

Special Issue: 中国科学院青年创新促进会合辑



吴波a,b,*(), 王冲a,b, 李宝林a,c, 王春儒a,b   

  1. a 中国科学院化学研究所 北京分子科学国家研究中心 分子纳米结构与纳米技术重点实验室 北京 100190
    b 中国科学院大学化学科学学院 北京 100049
    c 内蒙古大学化学化工学院 呼和浩特 010030
  • 投稿日期:2021-12-15 发布日期:2022-01-20
  • 通讯作者: 吴波
  • 作者简介:
  • 基金资助:
    国家自然科学基金(52072374); 国家自然科学基金(51772300); 国家自然科学基金(51832008); 中国科学院青年创新促进会(2018039)

Light-driven Molecular Magnetic Switch for a Metallofullerene

Bo Wua,b(), Chong Wanga,b, Baolin Lia,c, Chunru Wanga,b   

  1. a Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
    b School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
    c School of Chemistry & Chemical Engineering, Inner Mongolia University, Huhhot 010030, China
  • Received:2021-12-15 Published:2022-01-20
  • Contact: Bo Wu
  • About author:
    Dedicated to the 10th anniversary of the Youth Innovation Promotion Association, CAS.
  • Supported by:
    National Natural Science Foundation of China(52072374); National Natural Science Foundation of China(51772300); National Natural Science Foundation of China(51832008); Youth Innovation Promotion Association of CAS(2018039)

Metallofullerene Sc3C2@C80 was synthesized by the arc-discharging method and isolated by multi-stage high performance liquid chromatography. Two Sc3C2@C80 azobenzene nitroxide radical derivatives, compound I and II were synthesized through a Prato reaction, respectively. Usually, azobenzene undergoes trans-cis isomerization when irradiated with light tuned to an appropriate wavelength. The reverse cis-trans isomerization can be driven by light or occurs thermally in the dark. Thus, the compound I was excited by UV light, and it exhibited a strong absorption band decrease at around 340 nm and a slight increase at about 470 nm, which belonging to the π→π* and n→π* transition respectively. Similar to the azobenzene molecule in solution, the typical change of the absorption spectrum of compound I can be ascribed to the trans-to-cis transition with UV light irradiation. Similarly, the reverse isomerization of UV-irradiated compound I with visible light (475 nm) resulted in an obvious π→π* band increase, also indicating the reverse isomerization of compound I from cis-to-trans form. Besides, the structure and spin density distributions of compound I were calculated as well. It has two unpaired spins localizing on the Sc3C2@C80 moiety and nitroxide radical. The magnetic property of metallofullerene can be manipulated by the spin interactions of the two spin centers. The electron paramagnetic resonance (EPR) signals of the trans isomer of the compound I are almost independent of each other. After UV light irradiation, the distance of the two spin centers decreased to r=0.752 nm, and the strong spin-spin interaction weakened the EPR signals of Sc3C2@C80. However, the decreased chain length between Sc3C2@C80 and nitroxide radical would result in a weakened spin-lattice interaction, which increased the EPR signals of the nitroxide radical. Moreover, the UV-radiated compound I with visible light treated later for several minutes, and the EPR signals of Sc3C2@C80 has a certain degree of recovery with visible light irradiation. Therefore, the compound I has sensitive and reversible spin variation with different light irradiation. The remote nitroxide radical group serves as a magnetic switch for the EPR signal of Sc3C2@C80 through the photoisomerization properties of azobenzene bridge. The EPR signals of Sc3C2@C80 moiety were decreased by the strong spin-spin interaction, and the EPR signals of Sc3C2@C80 would be enhanced by larger space with visible light irradiation. Such magnetic switch for metallofullerenes has potential applications in quantum information processing and molecular devices.

Key words: metallofullerene, azobenzene, nitroxide radical, photoisomerization, molecular switch