Niklas Jens, Mardis Kristy L, Poluektov Oleg G
Chemical Sciences and Engineering Division , Argonne National Laboratory , Lemont , Illinois 60439 , United States.
Department of Chemistry, Physics, and Engineering Studies , Chicago State University , Chicago , Illinois 60628 , United States.
J Phys Chem Lett. 2018 Jul 19;9(14):3915-3921. doi: 10.1021/acs.jpclett.8b01613. Epub 2018 Jul 3.
Fullerenes attract much attention in various scientific fields, but their electronic properties are still not completely understood. Here we report on a combined EPR and DFT study of the fullerene anion C in solid glassy environment. DFT calculations were used to characterize its electronic structure through spin density distribution and magnetic resonance parameters. The electron spin density is not uniformly distributed throughout the C cage but shows a pattern similar to PCBM. EPR spectroscopy reveals a rhombic g-tensor sensitive to the environment in the frozen glassy solutions, which can be rationalized by deformation of the fullerenes along low-frequency vibrational modes upon cooling. DFT modeling confirms that these deformations lead to variation in the C g values. The decrease in g-tensor anisotropy with sample annealing is related to the lessening of g-tensor strain upon temperature relaxation of the most distorted sites in the glassy state.
富勒烯在各个科学领域都备受关注，但其电子性质仍未被完全理解。在此，我们报告了在固体玻璃态环境中对富勒烯阴离子C进行的电子顺磁共振（EPR）和密度泛函理论（DFT）联合研究。DFT计算用于通过自旋密度分布和磁共振参数来表征其电子结构。电子自旋密度并非均匀分布在整个C笼中，而是呈现出与聚碳酸亚乙烯酯（PCBM）相似的模式。EPR光谱显示，在冷冻的玻璃态溶液中，菱形g张量对环境敏感，这可以通过冷却时富勒烯沿低频振动模式的变形来解释。DFT建模证实，这些变形会导致C的g值发生变化。随着样品退火，g张量各向异性的降低与玻璃态中最扭曲位点温度弛豫时g张量应变的减小有关。
