期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 139, 期 50, 页码 18281-18287出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.7b09776
关键词
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资金
- JSPS
- Japan Agency for Science and Technology (CREST) [JPMJCR14L4]
- Japan Agency for Science and Technology (SEN-TAN)
- MEXT (ALPS Program)
- Project for Promoting Public Utilization of Advanced Research Infrastructure of MEXT, Japan
- Grants-in-Aid for Scientific Research [15H05696] Funding Source: KAKEN
Modern transition state, theory states that the statistical behavior of a chemical reaction is the sum of individual chemical events that occur randomly. Statistical analysis of each event for individual molecules in a three-dimensional space however is practically impossible. We report here that kinetics and mechanisms of chemical reactions can be investigated by using a one-dimensional system where reaction events can be observed in situ and counted one by one using variable- temperature (VT) atomic-resolution transmission electron microscopy (TEM). We thereby provide direct proof that the ensemble behavior of random events conforms to the Rice-Ramsperger-Kassel-Marcus theory, as illustrated for [2 + 2] cycloaddition of C-60 molecules in carbon nanotubes (CNTs). This method gives kinetic and structural information for different types of reactions occurring simultaneously in the microscopic view field, suggesting that the VT-TEM opens a new dimension of chemical kinetics research on molecules and their assemblies in their excited and ionized states. The study carried out at 393-493 K showed that pristine CNT primarily acts as a singlet sensitizer of the cycloaddition reaction that takes place with an activation energy of 33.5 +/- 6.8 kJ/mol. On the other hand, CNT suffers electron damage of the conjugated system at 103-203 K and promotes a reactive radical cation path that takes place with an activation energy of only 1.9 +/- 0.7 kJ/mol. The pre-exponential factor of the Arrhenius plot gave us further mechanistic insights.
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