摘要
由于碳笼的保护,从外部操控内嵌富勒烯笼内分子的特性一直是一个挑战.通过在顺磁性金属富勒烯Sc_(3)C_(2)@C_(80)碳笼外修饰具有光活性的偶氮苯-氮氧自由基,成功设计出基于金属富勒烯-氮氧自由基的分子开关,实现了原位可逆地光驱动远程控制金属富勒烯的顺磁特性.在不同光照条件下,利用偶氮苯的光异构化特性改变双自旋中心的相对位置,调整自旋-自旋、自旋-晶格相互作用,进而影响金属富勒烯的电子顺磁特性.研究发现,紫外光照下,氮氧自由基使金属富勒烯Sc_(3)C_(2)@C_(80)的顺磁信号逐渐减弱,可见光照下Sc_(3)C_(2)@C_(80)的顺磁信号又增强,由此实现了氮氧自由基作为顺磁开关的功能.
Metallofullerene Sc_(3)C_(2)@C_(80)was synthesized by the arc-discharging method and isolated by multi-stage high performance liquid chromatography.Two Sc_(3)C_(2)@C_(80)azobenzene nitroxide radical derivatives,compound I and II were syn-thesized 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 theπ→π^(*)and n→π^(*)transition respectively.Similar to the azo-benzene 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 obviousπ→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 Sc_(3)C_(2)@C_(80)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 Sc_(3)C_(2)@C_(80).However,the decreased chain length between Sc_(3)C_(2)@C_(80)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 Sc_(3)C_(2)@C_(80)has a certain degree of recovery
作者
吴波
王冲
李宝林
王春儒
Wu Bo;Wang Chong;Li Baolin;Wang Chunru(Beijing National Laboratory for Molecular Sciences,CAS Key Laboratory of Molecular Nanostructure and Nanotechnology,Institute of Chemistry,Chinese Academy of Sciences,Beijing 100190,China;School of Chemical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;School of Chemistry&Chemical Engineering,Inner Mongolia University,Huhhot 010030,China)
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2022年第2期101-104,共4页
Acta Chimica Sinica
基金
国家自然科学基金(Nos.52072374,51772300,51832008)
中国科学院青年创新促进会(No.2018039)资助.
关键词
金属富勒烯
偶氮苯
氮氧自由基
光致异构
分子开关
metallofullerene
azobenzene
nitroxide radical
photoisomerization
molecular switch
