Figure 7
Top-down (upper row) and side-view of a pair of contiguous rings in a stack: (a) hydrogen chloranilate anions in potassium hydrogen chloranilate dihydrate (Molcanov et al., 2009aBB20) stack in a nearly eclipsed fashion; (b) hydrogen bromanilate anions in RbHBA·3H2O form a staggered arrangement; (c) bromanilate dianions in K2BA·2H2O form offset stacks with a geometry similar to aromatic [pi]-interactions. The hydrogen bromanilate rings are not offset at all, whereas a very small offset (~ 0.2 Å) occurred in hydrogen chloranilate stacks. Offset of bromanilate dianions is necessary to prevent [pi]...[pi] repulsions between [pi] bonds from contiguous rings (e.g. C-O). H atoms of OH groups are not shown due to a disorder.  [article HTML]

© International Union of Crystallography 2012