THE IMPORTANCE OF INTERACTIONS BETWEEN METHYL-GROUPS AND AROMATIC RINGS IN HOMO AND HETERO-CYCLOPHANE STRUCTURES - A MOLECULAR MECHANICS AND X-RAY CRYSTALLOGRAPHIC INVESTIGATION

A series of macrocycles (L(1), L(2), L(3), L(4)) generated by the [2+3] Schiff base condensation of tris-2-aminoethylamine with a series of aromatic aldehydes have been investigated. The crystal structure of [L(3)], CHCl3, 2H(2)O is reported here to complete the set of structural data for these macrocycles. In all four structures, the three aromatic rings adopt a triangular disposition around the long ellipsoidal diameter, the N-br-N-br axis. In these structures, attractive H...pi interactions predominate and the conformations are rationalised by molecular mechanics calculations which show the importance of these interactions.