Acta Cryst. (2001). B57, 680-691 [doi:10.1107/S0108768101011193]
Abstract: The odd-alternant perchlorophenalenyl radical, C13Cl9, forms molecular stacks centered on crystallographic threefold rotation axes, but the spacing within the stacks (3.78 Å) is too large to allow good overlap of the orbitals in which the spin density is localized. The radical is ruffled because of the intramolecular repulsions between ![[alpha]](/logos/entities/alpha_rmgif.gif)
Cl atoms (the Cl
Cl peri interactions); the average displacement of an Cl atom from the molecular plane is 
0.7 Å. The deviations from molecular planarity do not, however, determine the spacing within the stacks, which is determined instead by interactions between stacks. The modulations found in the P3c1 superstructure are a response to the short interstack contacts that would occur in the average pseudocell structure (R
m, c' = c/6). The primary modulation is a pattern of enantiomeric alternation; a secondary modulation involves small rotations of the molecules around their threefold axes. The number (9) of independent molecules in the true cell is exceptionally large because of the conflict between the preference within the molecular stacks for threefold rotational symmetry and the preference in directions perpendicular to the stack axes for twofold alternation of enantiomers. The structural complexity reduces the precision of the distances and angles determined, but the average values found are in excellent agreement with those calculated by density functional theory.
Online 29 September 2001
 |   Structure factor file (CIF format) (514.6 kbytes) |
| Structure factor file (CIF format) (16.4 kbytes) |
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