Excitation-Dependent Triplet-Singlet Intensity from Organic Host-Guest Materials: Tunable Color, White-Light Emission, and Room-Temperature Phosphorescence.

A series of organic host-guest materials with multifunctional luminescence were constructed. Four isoquinoline derivatives were used as the guests, and benzophenone was used as the host. The doped system exhibited excellent dual emission with cyan fluorescence and orange-yellow room-temperature phosphorescence, and the dual emission could be combined into almost pure white-light emission. Importantly, the relative intensity of the fluorescence-phosphorescence could be adjusted by changing the excitation wavelength, with the phosphorescence intensity being significantly higher than the fluorescence intensity under shorter excitation wavelengths and vice versa under longer excitation wavelengths. Therefore, three-color emission switching among cyan, white, and orange could be achieved by simply adjusting the excitation wavelength. The results of experimental and theoretical calculations indicated that the excitation-dependent emission colors were caused by different transfer paths for excitons under different excitation wavelengths. These materials with multifunctional luminescence could be used as writable inks for advanced anticounterfeiting.