Excimer Diffusivity in 9,10-Bis(phenylethynyl)anthracene Assemblies on Anodic Aluminum Oxide Membranes

Excimers usually serve as low energy trap sites in supramolecular chromophore assemblies; however, if the trap is not too deep, excimers may diffuse throughout the structure, making it possible to deliver excitation energy to distant sites. To investigate this phenomenon, a supramolecular assembly of 9,10-bis­(phenylethynyl)­anthracene (BPEA) chromophores was prepared by covalently linking a BPEA molecule to the walls of nanoporous anodic aluminum oxide (AAO) membranes. The BPEA molecules self-associate and form excimers upon photoexcitation. Excimer formation in the BPEA assemblies on the AAO membranes is a multistep process and involves intermolecular structural reorganization between the chromophores. Describing the system using exciton theory reveals that the BPEA excimer is mobile, despite its frequent role as a lower energy trap state. The excimer diffusivity in the BPEA on the AAO membranes is higher than that of other reported excimers, approaching that of singlet excitons in efficient organic photovoltaic systems.