F-19 NMR-, ESR-, and vis-NIR-spectroelectrochemical study of the unconventional reduction behaviour of a perfluoroalkylated fullerene: dimerization of the C-70(CF3)(10)(-) radical anion

摘要

The most abundant isomer of C-70(CF3)(10) (70-10-1) is a rare example of a perfluoroalkylated fullerene exhibiting electrochemically irreversible reduction. We show that electrochemical reversibility at the first reduction step is achieved at scan rates higher than 500 V s(-1). Applying ESR-, vis-NIR-, and F-19 NMR-spectroelectrochemistry, as well as mass spectrometry and DFT calculations, we show that the (70-10-1)(-) radical monoanion is in equilibrium with a singly-bonded diamagnetic dimeric dianion. This study is the first example of F-19 NMR spectroelectrochemistry, which promises to be an important method for the elucidation of redox mechanisms of fluoroorganic compounds. Additionally, we demonstrate the importance of combining different spectroelectrochemical methods and quantitative analysis of the transferred charge and spin numbers in the determination of the redox mechanism.