A conical intersection model to explain aggregation induced emission in diphenyl dibenzofulvene

A conical intersection seam is behind the restriction of intramolecular rotation mechanism for aggregation induced emission in diphenyl dibenzofulvene (DPDBF). In solution, the seam is accessed through rotation around the exocyclic fulvene bond, leading to radiationless decay to the ground state. In the solid, the seam cannot be accessed because the torsion is blocked, and DPDBF becomes emissive.