Multicolor and White-Light Emission from a Pt(II)-Metallacycle via Excited-State Modulation

Abstract

Coordination-driven self-assembly enables the construction of discrete supramolecular coordination complexes (SCCs) with well-defined geometries, but metallacycles showing multicolor or white-light emission via ligand excited-state modulation remain rare. Here, we report a multicolor photoluminescent metallacycle M assembled from a triphenylamine-based dipyridine ligand L1 and a benzothiadiazole-based diplatinum(II) ligand L2. M exhibits solvatochromic fluorescence, appearing purple in toluene, white in ethyl acetate and THF, and red in DMSO. Femtosecond transient absorption spectroscopy reveals the multicolor luminescence mechanism. For L1, the relaxation pathway shifts from a locally excited state to charge-transfer (CT) states with increasing solvent polarity, while L2 undergoes ultrafast intersystem crossing to a long-lived triplet state. Within M, coordination-induced metal-to-ligand charge transfer (MLCT) suppresses fluorescence resonance energy transfer (FRET) between L1 and L2, enabling multicolor emission. This work provides a new strategy for constructing multicolor and white-light-emitting metallacycles, with promising applications in optoelectronics and bioimaging.