NMR Properties of Polylithiated C60

✍ Scribed by M. Bühl

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: German
• Weight: 108 KB
• Volume: 626
• Category: Article
• ISSN: 0372-7874
• DOI: 10.1002/(sici)1521-3749(200002)626:2<332::aid-zaac332>3.0.co;2-q

✦ Synopsis

Endohedral, 13 C, 7 Li, and nucleus-independent (NICS) chemical shifts are reported for selected Li n C 60 isomers (n = 6, 12, 18) at the GIAO (gauge-including atomic orbitals)-SCF/DZP//BP86/3±21G level. Li 6 C 60 closely resembles C 60 6± in terms of NMR criteria for aromaticity, as evidenced by an exceptionally high endohedral shielding. In contrast, nonaromaticity is indicated for Li 12 C 60 , based on a positive endohedral chemical shift. NICS and d(endo) values very similar to those of Li 12 C 60 are obtained for Li 18 C 60 . According to population analysis, indeed the same number of electrons are transferred to the fullerene cage in both cases. Endohedral chemical shifts, accessible via 3 He NMR of the corresponding endohedral helium compounds, could thus be a valuable indicator for the extent of reduction of the C 60 molecule. Energetic estimates suggest that in the bulk, Li 12 C 60 should be unstable with respect to decomposition into Li 6 C 60 and lithium metal.