Excitation Wavelength Dependent Fluorescence and Phosphorescence from Organic Ionic Crystalline Powder

A new type of material, organic salts in the crystal and crystalline powder state, with both excitation wavelength dependent (Ex-De) fluorescence and Ex-De phosphorescence under ambient conditions have been reported. The single component triphenylsulfonium chloride displays tunable fluorescent colors ranging from light purple to sky blue and tunable afterglow colors varying from green to yellowish green, to yellow (lifetimes: 57, 141, 66 ms, afterglow lasting for 2.1, 2.0, 2.3 s). The relationship between the structure and luminescence performance of 17 sulfonium salt derivatives confirms the pivotal roles of both the anions and the electronic and steric effect of substituent factors for luminescence. Single-crystal analysis reveals that unique ionic bonding and intermolecular interaction can promote an ordered arrangement of organic salts in a crystal state, which then can facilitate molecular aggregation for phosphorescence generation. Theoretical calculations have also confirmed this viewpoint. More importantly, these sulfonium salt derivatives can be used for advanced multimodal anti-counterfeiting and mitochondrial imaging, respectively. This study has not only expanded the scope of Ex-De materials but also extended their applications.