Phosphine Oxide-Metal Chelated Cuprous Iodide Hybrids with Rich Structural Architectures and Tunable Emission

Eco-friendly metal halides have emerged as promising luminescent materials due to their tunable optoelectronic properties and scalable processability. Herein, we present a novel family of phosphine oxide-metal chelated cuprous iodide hybrids (POCI), where phosphine oxide-chelated Group I/II metal cations serve as counterions to engineer diverse crystalline architectures. By employing trimorpholinophosphine oxide (TMPO) as the ligand, eight new compounds with the general formula [TMPO]₂M_1-2·xH₂O[Cu₂I₄] were synthesized through a controlled slow evaporation method. The compounds display a rich variety of structural architectures where differences in the cationic coordination frameworks significantly influence their luminescent properties. The approach was extended to tricyclohexylphosphine oxide (TCPO) and triphenylphosphine oxide (TPPO), yielding [TCPO]₈Na₂[Cu₅I₇] and [TPPO]₃Mg·2H₂O·C₃H₆O[Cu₄I₆] with distinct copper clusters. The distinct emission behaviors observed in these compounds can be ascribed to different excited-state mechanisms, including self-trapped exciton (STE) emission, metal-to-ligand charge transfer/halide-to-ligand charge transfer (MLCT/HLCT), and cluster-centered (CC) excited states. Remarkably, these materials can be prepared via scalable mechanochemical synthesis and exhibit exceptional thermal stability, enabling their direct incorporation into hot-melt adhesives. The resulting materials process into flexible films and 3D-printing architectures with spatially controlled emission, establishing a platform for sustainable, high-performance phosphors compatible with industrial manufacturing.