Reversible single-molecule white light based on controllable fluorescence resonance energy transfer

Two novel Diels-Alder exo-adduct donor-acceptor dyes were synthesized with different spacer lengths. These dyes display intramolecular fluorescence resonance energy transfer (FRET) from a deep-blue-emitting naphthalimide donor to a yellow-emitting dansyl acceptor. Temperature-responsive bond cleavage and spacer length modulation achieve controllable intramolecular FRET, enabling reversible single-molecule white-light emission.