Effect of Xenon on Fullerene Reactions

摘要

Solutions containing ~3He@C_(60), ~(129)Xe@C_(60), and varying amounts of 9,10-dimethylanthracene (DMA) were allowed to reach equilibrium, and the ~3He and ~(129)Xe NMR spectra were taken at the same temperature. Each spectrum showed peaks for the unreacted X@C_(60) and for the monoadduct. The ratios of the peak heights show that the included xenon atom substantially changes the equilibrium constant. This change is temperature dependent, meaning that the xenon atom changes both AH and AS for the reaction. DMA is more reactive with He@C_(60) at low temperatures and with Xe@C_(60) at higher temperatures. The difference in chemical shift between the monoadduct and the unreacted X@C_(60) is more than twice as large for Xe than for He and in the opposite direction. Calculations show that the electron density in Xe@C_(60) is higher than that in empty C_(60) on the outside of the cage.