Fullerenols Revisited as Stable Radical Anions
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- 作者：Lars O. Husebo ; Balaji Sitharaman ; Ko Furukawa ; Tatsuhisa Kato ; and Lon J. Wilson
- 刊名：Journal of the American Chemical Society
- 出版年：2004
- 出版时间：September 29, 2004
- 年：2004
- 卷：126
- 期：38
- 页码：12055 - 12064
- 全文大小：446K
- 年卷期：v.126,no.38(September 29, 2004)
- ISSN：1520-5126
文摘
The first exhaustive purification and characterization of the much-studied "fullerenols", preparedby reaction of C60 in toluene with an oxygenated, aqueous NaOH solution using tetrabutylammoniumhydroxide as a phase transfer catalyst, has been performed. The resulting fullerenol is not simplypolyhydroxylated C60 but rather is a structurally and electronically complex C60 radical anion with a molecularformula of Na+n[C60Ox(OH)y]n- (where n = 2-3, x = 7-9, and y = 12-15) for three different, but identical,preparations. Surprisingly, Na+-fullerenol is paramagnetic, exhibiting 
B values in aqueous solution of 1.9-2.1 B.M. at 0.5 T and 300 K and R1 proton relaxivities of 0.55-0.77 mM-1s-1 at 20 MHz and 40 
C, valuesboth slightly higher than those expected for a pure S = 1/2 spin system. ESR studies (ESE-FS and 2Dnutation) of frozen aqueous solutions at 1.5 and 5.0 K establish that Na+-fullerenol is mainly S = 1/2 witha minor, but significant, component of S = 1. Thus, this is the first report to characterize these widelystudied, water-soluble fullerenols as stable radical anions. The stability of the S = 1/2 Na+-fullerenol radicalis likely due to a highly derivatized C60 surface that protects a cyclopentadienyl radical center on the fullerene.
B values in aqueous solution of 1.9-2.1 B.M. at 0.5 T and 300 K and R1 proton relaxivities of 0.55-0.77 mM-1s-1 at 20 MHz and 40 C, valuesboth slightly higher than those expected for a pure S = 1/2 spin system. ESR studies (ESE-FS and 2Dnutation) of frozen aqueous solutions at 1.5 and 5.0 K establish that Na+-fullerenol is mainly S = 1/2 witha minor, but significant, component of S = 1. Thus, this is the first report to characterize these widelystudied, water-soluble fullerenols as stable radical anions. The stability of the S = 1/2 Na+-fullerenol radicalis likely due to a highly derivatized C60 surface that protects a cyclopentadienyl radical center on the fullerene.