In the [2.3](2,7)phenanthrenophanes prepared by the intramolecular [2 + 2]
photocycloaddition of 1,3-bis(7-vinyl-2-phenanthryl)propane, excimer fluore
scence was observed for not only syn- but also anti-isomer, though the maxi
mal position of the latter was slightly blue-shifted relative to the former
.