Coordination‐Driven Pt(II)‐Ru(II) Heterometallacycles With Ultrastrong Cathodic Electrochemiluminescence and Guest‐Responsive Signal Amplification

ABSTRACT Coordination‐driven self‐assembly enables the integration of multiple functional elements within a single supramolecular architecture. By combining emissive chromophores, optimized electronic structures, and confined microenvironments, it provides an effective strategy for enhancing cathodic electrochemiluminescence (ECL). Here, we report a discrete Pt(II)‐Ru(II) heterometallacycle constructed by embedding a Ru(II) polypyridyl luminophore into a positively charged Pt(II)‐based metallacyclic scaffold. The assembly reorganizes the frontier electronic structure through orbital redistribution and enhanced delocalization while preserving the intrinsic Ru(II)‐centered emissive excited state, thereby enabling efficient coupling between electrochemical reduction and excited‐state formation. Consequently, the heterometallacycle exhibits dramatically enhanced cathodic ECL, demonstrating that supramolecular electronic reconfiguration can overcome the intrinsic limitations of molecular luminophores. The positively charged cavity further enables 1:1 host–guest complexation with terephthalate dianions, and guest encapsulation modulates the local electronic environment to produce an additional ECL enhancement. Notably, the binding constant determined by ECL titration agrees well with that obtained from fluorescence titration, establishing ECL as a complementary signal transduction modality for probing host–guest recognition. This work demonstrates that coordination‐driven self‐assembly enables the synergistic integration of emissive chromophores, electronic regulation, and guest‐responsive supramolecular microenvironments, providing new design principles for supramolecular cathodic ECL systems.