STRUCTURE OF 2,3-DIPHENYL-2-NORBORNENE - COMPARISON WITH DATA FOR A CIS-STILBENE

The molecule 2,3-diphenyl-2-norbornene (2,3-diphenylbicyclo[2.2.1]hept -2-ene) (1) has been prepared as a model for cis-stilbene (2) in which single-bond but not double-bond torsion (within the pi system) is ste rically possible on both the ground-state and lowest triplet-state sur faces. A comparison of the crystal structure of (1) with previously pu blished data for a derivative of (2) shows that the non-planar pi-syst em geometries of (1) and (2) are indeed similar. This has allowed defi nitive conclusions to be drawn concerning the phenomenon of 'nonvertic al' triplet-energy transfer.