Comparison of flexibly and rigidly bridged donor‐acceptor systems; solvent induced switching between folded and extended emissive charge‐transfer states

Aniline and naphthalene chromophores were linked by either a flexible trimethylene chain (in 1) or a semirigidly extended piperidine ring (in 2). While 1 undergoes photoinduced intramolecular electron transfer in all solvents 2 does so only in more polar solvents, indicating that solvent stabilization is required to make this process feasible at the donor‐acceptor distance imposed in 2. In both 1 and 2 charge recombination is accompanied by exciplex‐type emission which, in polar solvents, appears to stem from a conformationally extended conformation devoid of extensive direct overlap between the chromophores.