New aryl edge-edge packing interactions involving the N-oxide functional group

The X-ray crystal structures of 5b,6,12b,13-tetrahydropentaleno[1,2-b:4,5-b ']diquinoline 5,12-dioxide (5) and (6 alpha,7 alpha,14 alpha,15 alpha)-7,15 -dibromo-6,7,14,15-tetrahydro-6,14-methanocycloocta[1,2-b:5,6-b']diquinolin e 5,13-dioxide (6) reveal two new packing modes of potential importance as supramolecular synthons for molecular assembly. Both involve intermolecular edge-edge association of an aryl ring and an N-oxide functionality. One is a bifurcated Ar-H ... O(N)... H-Ar interaction which on repetition gives i nfinite chains of the molecules. The second is a 10-membered centrosymmetri c dimer also involving Ar-H ... O-N interactions but which merely links two neighbouring molecules of (6). The latter arrangement is a structural anal ogue of a recently reported dimeric centrosymmetric eight-membered Ar-H ... N synthon.