MACROCYCLIC (1,3)-BENZENA-(1,4)-PIPERAZINACYCLOPHANES AND (1,4)-BENZENA-(1,4)-PIPERAZINACYCLOPHANES

New large, up to 45-membered macrocycles were synthesised from piperaz ine and m- and p-2,6-bis (bromomethyl)xylene under high dilution condi tions. X-ray structures of compounds 3a, 4a, 5a, and 8b were determine d. Surprisingly, none of the macrocycles prepared showed any inclusion properties towards small guest molecules. Instead, the compounds were found to self-organize during the packing process into larger structu res due to the complementary of the molecular skeletons. In the crysta lline state 3a forms nets, where the macrocycles are bound by H-C-H .. . N interactions to each other. 4a exits in a dimeric structure, which , in turn, further extends to a sheet structure. The positively charge d phane 8b (di-dihydrochloride salt) adopts a chair-chair conformation , confirming that protonation of the N atoms does not change the confo rmation.