C-60 CARBYNE KNOTS (FROM 0(1), TO 6(3)) - THEORETICAL NMR-SPECTRA

The structure, stability, and theoretical C-13- NMR spectra of nonline ar C-60 carbon clusters of the carbyne type have been estimated by ab initio calculations. Semiempirical AM1 calculations have shown the kno t-cycle energy difference to increase with the number of knot crossing s and to decrease with the number of atoms constituting the molecule. Some C-60 carbyne prime knots belong to the following symmetry point g roups: D-30h for cycle, D-3 for trefoil, C-1 for figure eight (but S-4 for the C-64 figure eight), C-2 for cinquefoil and the other five-cro ssing knot, and C-1 for six crossing knots. Knot symmetry and the calc ulated C-13-NMR qualitative spectra provide the basis for experimental identification of the knotted carbyne structures. (C) 1998 John Wiley & Sons.