The intramolecular π-polarization induced upon binding the bichromophoric ligand L1 to lanthanide ions produces intermolecular hetero-π-stacked pyrene-terimine organization in the resulting complexes as ascertained by ground state supramolecular aggregations leading to dimeric [L1Ln(hfac)₃ ]₂ (Ln = Y, Eu) units both in the solid state (X-ray crystal structure determination) and in dichloromethane solution (¹ H NMR titrations). Photoexcitation engenders additional polarization changes which further complicate/extend interaromatic aggregation processes via the formation of light-driven excimers and exciplexes. The various π-stacking intermolecular interactions operating in the [L1Y(hfac)₃ ] host are probed by reaction with three competitive aromatics guests: electron-poor nitrobenzene, neutral benzene and electron-rich methoxybenzene.