Dual Guests Synergistically Tune the Phosphorescence Properties of Doped Systems through Chemical Interactions with Bases

It is a trend to construct multicomponent room temperature phosphorescence/RTP doped materials in the future to improve phosphorescence performance by using the advantage that the host in the doped system can be used as a container containing other components. Herein, the multicomponent doped systems are constructed with two isoquinoline derivatives (OxISQ and PrISQ) as the guests, diphenyl sulfoxide/SDB as the host, and alkali (KOH) as the fourth component. Bicomponent doped material OxISQ/SDB has strong cyan RTP, whereas PrISQ/SDB has almost no RTP activity. The effect of KOH on the phosphorescence intensity of OxISQ/SDB is excitation-dependent. When λex = 365 nm, KOH turns off the phosphorescence emission, revealing the intensity of KOH-added three-component doped material OxISQ/SDB/KOH is significantly weaker than that of OxISQ/SDB, whereas KOH exhibits the turn-on property for OxISQ/SDB at λex = 385 nm. For PrISQ/SDB, KOH displays permanent turn-on ability, and PrISQ/SDB/KOH has strong yellow-orange RTP. More deeply, a two-guest four-component doped system OxISQ/PrISQ/SDB/KOH is constructed, and from OxISQ/PrISQ/SDB to OxISQ/PrISQ/SDB/KOH, with the increase of KOH, the phosphorescence colors gradually change from cyan to green to yellow to orange at λex = 365 nm, but the color only can change directly from cyan to yellow-orange at λex = 385 nm. In addition, OxISQ/PrISQ/SDB/KOH exhibited a time-dependent afterglow color from orange-yellow to cyan over 2 s due to the different phosphorescence lifetime, intensity, and wavelength of each component. The experimental results confirmed that phenylhydroxyl-containing guests react with KOH to form organic salts, thereby inducing new excitation and emission wavelengths in the doped materials. This work is the first to construct a four-component doped system with dual guests that can undergo chemical reactions. Moreover, taking advantage of the water solubility of KOH, the doped materials have achieved advanced anticounterfeiting writing and printing in the aqueous phase.