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

The monosubstituted derivative 4- ethynyl[ 2.2] paracyclophane, C18H16, ( I), and the four disubstituted isomers, 4,12-, ( II), 4,13-, ( III), 4,15-, ( IV), and 4,16- diethynyl[ 2.2] paracyclophane, ( V), all C20H16, show the usual distortions of the [ 2.2] paracyclophane framework. The crystal packing is analyzed in terms of C - H center dot center dot center dot pi interactions, some with H center dot center dot center dot pi as short as 2.47 ,angstrom 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.