C-H...pi interactions in five ethynyl-substituted [2.2]paracyclophanes: further examples of the '7,11' packing pattern.

The monosubstituted derivative 4-ethynyl[2.2]paracyclophane, C(18)H(16), (I), and the four disubstituted isomers, 4,12-, (II), 4,13-, (III), 4,15-, (IV), and 4,16-diethynyl[2.2]paracyclophane, (V), all C(20)H(16), show the usual distortions of the [2.2]paracyclophane framework. The crystal packing is analyzed in terms of C-H...pi interactions, some with H...pi as short as 2.47 A, in which the cyclophane rings and/or the triple-bond systems may act as acceptors. For compounds (I) and (IV), the known '7,11'-type cyclophane packing is observed, with a herring-bone pattern of molecules in a layer structure.