Belt-Shaped Cyclophanes via Photodimerization of Phenanthro-Condensed [18]Annulenes

A novel cyclophane type can be obtained by photocyclodimerization reactions of condensed [18]annulenes. Quantitative yields in pure columnar liquid crystalline phases and high yields in 10-6 M solution raise the inquiry about the unusual dimerization mechanism in this process. Concentration-dependent measurements of the emission and excitation spectra and the fluorescence lifetimes reveal a ground state aggregation in solution even at very low concentrations.