Aromatic cation-π induced multifluorescence tunable two-dimensional co-assemblies for encoded information security.

The field of light-emitting two-dimensional co-assemblies (2DCAs) is extending rapidly. Nevertheless, multifluorescence tunable 2DCAs are relatively underdeveloped, because the exploration of novel assembly strategies and noncovalent interactions to realize desirable photophysical features is still difficult. Herein, we present the first implementation of an aromatic cation-π interaction induced emissive charge transfer strategy for multifluorescence tunable 2DCAs, which are derived from fluorophore anthracene-based monomers and planar aromatic cations (pyrylium and tropylium). Benefiting from the aromatic cation-π interactions between anthracene and cationic guests, well-regulated 2DCAs are thus successfully obtained. The resultant 2DCAs exhibit a broadened fluorescence tunable range between blue-green and red emission colors, which is simply realized by varying the solvent ratio to turn on/off the aromatic cation-π emission charge transfer in the assembly/disassembly state of 2DCAs. On this basis, the programmable numbers, letters, patterns, and 3D codes with co-assembly encoded information security functions are successfully fabricated on papers, which would have a positive impact on developing supramolecular encryption materials.