Multichromophoric π-Conjugation: Modular Design for Gated and Cascade Energy Transfer

Multichromophore arrays allow for cascade energy transfer. As an isoelectronic analogue of indacenyl, bis(triazolo)benzene features a fused tricyclic skeleton that rigidly places two π-extended triazoles in close proximity. Such triazole-based fluorophores behave as electronically independent modules in the ground states, but become tightly coupled upon photoexcitation for highly efficient excitation energy transfer (EET) that can be gated by external stimuli. Taking this donor-acceptor fluorophore system a step further, we have designed and implemented a cascade EET. Here, the initial excitation takes part in a circular relay to arrive at the longest-wavelength emitting site as the final destination. Modularly constructed triazoloarenes should serve as versatile platforms for chemically controlled optical signaling.