Pillararene-based tunable luminescent materials via supramolecular assembly-induced Förster resonance energy transfer enhancement†
Pillararene tetramers with tetraphenylethene cores and different lengths of alkyl ether chains (H1-4C4P and H2-2C4P) and a 9,10-distyrylanthrace-bridged neutral guest linker (DSA-G) are synthesized to fabricate tunable solid-state fluorescent materials through supramolecular assemblies of DSA-G⊂H1-4C4P and DSA-G⊂H2-2C4P. Their fluorescence emission is strongly enhanced and their colors are changed upon assembly, which can be ascribed to the supramolecular assembly-induced enhanced emission and Förster resonance energy transfer (FRET) processes between H1-4C4P (or H2-2C4P) and DSA-G. Both ensembles of DSA-G⊂H1-4C4P and DSA-G⊂H2-2C4P exhibit thermo and solvent dual-responsive features, while DSA-G⊂H2-2C4P shows higher sensitivity toward external stimuli as compared to DSA G⊂H1-4C4P due to the shorter distance between fluorophores. The use of these fluorescent materials as inks confirms their efficiencies in the solid-state, paving the way for new potential applications of smart optical materials based on supramolecular assemblies.