Aliphatic Ligand‐Mediated Cu–Cu Distance Tuning Enables Near‐Unity Efficient and Color‐Tunable Circularly Polarized Luminescent Copper(I) Iodide Clusters

Copper(I) iodide clusters are emerging as a new generation of multi‐color circularly polarized luminescence (CPL) materials due to their exceptional luminescent properties and tunable electronic characteristics. However, the substantial decrease in photoluminescence quantum yield (PLQY) during emission color tuning has remained a major challenge for developing high‐performance CPL materials. Herein, diverging from conventional ligand‐involved charge‐transfer mechanisms for color tuning, we employ structurally related aliphatic ligands to reduce ligand‐involved contributions and promote cluster‐centered emission mainly associated with the inorganic [Cu 4 I 4 ] core. Subtle ligand modifications preserve the rigid [Cu 4 I 4 ] cluster framework while reinforcing hydrogen‐bonding networks, inducing variable compression of Cu–Cu distances, enabling continuous emission tuning from green (550 nm) to red (633 nm) while maintaining ultrahigh, near‐unity PLQY. Moreover, the introduction of chiral ligands induces CPL activity with a luminescence dissymmetry factor ( g lum ) reaching 2.3 × 10 − 3 . These remarkable performances render these Cu–I clusters promising for anticounterfeiting and encryption applications. Overall, this work demonstrates the integration of near‐unity PLQY with tunable CPL in metal hybrid clusters, providing a new strategy for high‐performance multicolor CPL materials.