Supramolecular Control of Dual Emission in Macrocycle-Confined Dimers

Control over luminescent properties is conventionally achieved by designing rigid, static packing geometries. Yet, chromophores within these assemblies naturally undergo continuous relative motion; harnessing this often-overlooked dynamic flexibility to actively dictate excited-state outcomes offers a powerful new dimension in materials design. Here, we introduce a supramolecular strategy to systematically control dual emission by restricting the structural dynamics of macrocycle-confined dimers. Utilizing cucurbit[8]uril (CB[8]) and bis(phenylpyridinium) (BPP) guests, we construct precise 2:1 and 2:2 host–guest complexes to establish dynamic and static mobility limits within a unified framework. Cavity-confined dimerization induces a unique intrinsic dual emission. By progressively tightening structural restriction—moving from the fluxional 2:1 complex to the clamped 2:2 architecture, and further to a rigidly sodium-bridged framework—the dominant emission cleanly shifts from a short-wavelength state to a long-wavelength state, accompanied by a dramatically enhanced fluorescence quantum yield. Time-resolved spectrosco-py reveals that this supramolecular confinement actively governs the kinetics of excited-state relaxation, definitively linking mo-tional freedom to the resulting functional photoluminescence. Collectively, these results showcase the controlled restriction of supramolecular dynamics as an innovative, general design principle for tailoring programmable optoelectronic materials.