A Modular Approach\nto Tuning Emissive <i>N</i>‑Quinolyl Through-Space\nCharge Transfer States Using sp<sup>3</sup>‑Scaffolds

We have shown that palladium-catalyzed cascade processes\nprovide\nmodular access to rigid quinoline-containing tetracyclic amines. This\nmodular approach enables fine-tuning of the through-space charge transfer\n(TSCT) state formation between the lone pair localized on the nitrogen\natom in the cage moiety and the quinoline moiety by variation of both\nthe intramolecular <i>N</i>-aryl distance and quinoline\nsubstitution. Decreasing this <i>N</i>-aryl distance enhances\nthe formation of the TSCT species, giving control over the emission\ncolor and photoluminescence quantum yield. Methoxylation of the quinoline\nunit decreases the propensity of TSCT formation. The development of\nthis structure–activity relationship provides great insight\nfor TSCT formation with an impact on further understanding dimeric,\nexcimeric, and exciplex species. This understanding is crucial for\nthe work underpinning their use in biosensor applications, and the\nconclusions are of relevance to the broader field of photoluminescence.