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

The influence of preorganised 7,7-diphenylnorbornane in the stability (K-a) of host-guest complexes as well as in the determination of the energy of e dge-to-face aromatic interactions has been investigated. The guest molecule s studied bind more strongly with hosts that contain the cofacial 7,7-diphe nylnorbornane subunit than with similar hosts that have a 1,1-diphenylcyclo hexane subunit. On the other hand, the value of the edge-to-face aromatic i nteractions calculated for our complexes (-0.2 +/-0.6 kJ mol(-1)) is signif icantly lower (by a factor of seven) than the one previously reported in th e literature. This result highlights the importance of entropic factors in the determination of weak noncovalent interactions.