Synthesis and ring opening reaction of octaoctyl substituted [2.2.2.2](2,7)-fluorenophanetetraene by photooxidation

Abstract

Octaoctyl substituted fluorenophanetetraene has been synthesized from its corresponding octaoctyl substituted tetrathia[3.3.3.3]fluorenophane followed by benzyne Stevens rearrangement, oxidation and thermal elimination. The solid-state structure of octaoctyl substituted [2.2.2.2](2,7)-fluorenophanetetraene reveals that fluorene units are connected by cis vinylenes and alkyl chains are located inside and outside the rings. The photooxidation reaction of the fluorenophanetetraene was carried out in a dilute solution under UV light irradiation to give all trans linear fluorenevinylene with aldehyde end groups. The optical properties of the fluorenophanetetraene and its linear compound generated by photooxidation have been investigated and compared. The fluorescence quantum yield of the fluorenophanetetraene in solution is much lower than that of its linear compound generated by photooxidation due to shorter effective conjugation lengths; however, the fluorescence intensity of the fluorenophanetetraene in the solid state is much higher than that of its linear compound generated by photooxidation possibly due to weak intermolecular interaction.