Beating the Odds with Binuclear N‐Heterocyclic Carbene Metallacycles: A Practical and Efficient Full‐Color Tunable Fluorescence System

Abstract Achieving full‐color emission with just two emitters presents a significant challenge. Two N‐heterocyclic carbene metallacycles ( NHC‐M ; M ═ Ag, Au) featuring a tetraphenylethene core, combining covalent and coordination bonds are synthesized to restrict rotation within the NHC‐M‐BC (BC = bicyclic) metallacycles and greatly enhanced their quantum yields. The enhancement is accomplished by adjusting the CH 3 CN/H 2 O solvent mixture, allowing emission tuning from blue to green for NHC‐Ag‐BC . Further diversification of the emission spectrum, including access to high‐quality white light (CIE coordinates 0.33, 0.34), is facilitated through the addition of sulforhodamine B via fluorescence resonance energy transfer (FRET). The compatibility of NHC‐Ag‐BC with agarose gel extends its applicability to UV‐LEDs chromic coatings, as well as information encryption and anti‐counterfeiting materials. The results underscore the viability of dual‐fluorophore systems for achieving full‐color emission and highlight the potential for developing versatile, multi‐colored functional materials.