Aggregated-induced emission as a photophysical mechanism of interest is also intimately connected to internal conversion; compounds which display pronounced photophysical properties when aggregated are aggregation-induced emitters. With the first models proposing control over loss mechanisms based on intramolecular rotational restriction as a method to promote the mechanism , it becomes obvious that were otherwise free normal modes, like twisting or rotational modes, to be restricted or locked in place, internal conversion could be damped with respect to the monomer phase. A good example of this process are compounds with biaryl groups ; in the monomer phase they are free to rotate and can be labelled as the promoting mode in internal conversion, while in the solid state, this rotation is forbidden. See Ref. 398 for a review on good review on aggregation-induced phenomena.