Reversibly photoswitchable dual-color (blue ⇆ green) phosphorescence from β-cyclodextrin inclusion complex materials

We report herein two new supramolecular materials based on beta-cyclodextrin inclusion complex samples with partially included organic radicals, which emit blue phosphorescence (excitation at 365 nm), and exhibit higher phosphorescent quantum yields (9.5 and 20.3%). However, purely organic radicals emit green phosphorescence, and possess low quantum yields (1.8 and 3.3%). One inclusion complex material exhibits the reversible dual-color (blue <-> green) switching behavior in the response to ultraviolet and visible light stimuli, respectively: upon excitation with ultraviolet light (365 nm), it emits blue phosphorescence with quantum yield of 9.5%; however, it emits green phosphorescence and possesses higher quantum yield of 29.0%, upon irradiation by visible light (425 nm). The reversibly photoswitchable behavior is probably ascribed to the light-driven guest molecular conformation conversions in the beta-cyclodextrin cavities. This light-responsive dual-color phosphorescent supramolecule is unique in terms of molecular conformation conversions. (C) 2013 Elsevier Ltd. All rights reserved.