Influence of highly preorganised 7,7-diphenylnorbornane in the free energy of edge-to-face aromatic interactions.

The influence of preorganised 7,7-diphenylnorbornane in the stability (Ka) of host-guest complexes as well as in the determination of the energy of edge-to-face aromatic interactions has been investigated. The guest molecules studied bind more strongly with hosts that contain the cofacial 7.7-diphenylnorbornane subunit than with similar hosts that have a 1,1-diphenylcyclohexane subunit. On the other hand, the value of the edge-to-face aromatic interactions calculated for our complexes (-0.2 +/- 0.6 kJmol(-1)) is significantly lower (by a factor of seven) than the one previously reported in the literature. This result highlights the importance of entropic factors in the determination of weak noncovalent interactions.