To examine the steadiness of this characterization, we displaced the geometry at intervals along 4 degrees of freedom relative to the heterodimer planes ( Specifically, no level inversion between the dark and bright state occurs until the separation between perylene diimide and pyrene is larger than 6.5 Å (Figure ). This interaction is well known in bichromophoric molecules or co-crystals, especially in the case of pyrene coupled to perylene derivatives.