Generating, visualizing and tuning π-π interactions in metal-induced supramolecular assembly.

This work emphasizes the role of metal complexation for controlling and tuning static/dynamic π-stacked organizations responsible for the programmed light emission of the bichromophoric pyrene-terimine ligand L2 upon photoexcitation. Its binding to the closed-shell trivalent yttrium guest [Y(hfac)3] (hfac = 1,1,1,5,5,5-hexafluoro-pentane-2,4-dione) provides a diamagnetic heteroleptic [L2Y(hfac)3] adduct for which the static intramolecular pyrene-pyrene excimer emission operating in the free ligand L2 is transformed into a dynamic intramolecular pyrene-pyrene excimer emission in the resulting complex. The transition from static-to-dynamic intramolecular excimers results in an enhanced sensitivity toward interactions with electron-poor nitrobenzene guests, which is supported by a considerable Stern-Volmer quenching constant measured for [L2Y(hfac)3]. This demonstrates that the metal-directed organization of the polyaromatic ligand in [L2Y(hfac)3] can boost the excimeric chemical sensing of target aromatic analytes.