Intermolecular hydrogen-bonding effects on excited-state competition for near-unity emission in copper(I) iodide hybrids with cationic ligands.

Copper(I) halide hybrid materials offer a versatile platform for tunable photoluminescence, with potential applications in light-emitting devices and scintillators. However, clarifying how structural features influence their photophysical properties remains important for their further development. Herein, we report two novel Cu(I)-iodide "All-in-One" (AIO) hybrids synthesized from a phosphine-amine ligand that undergoes preferential N-protonation, enabling simultaneous ionic and Cu-P coordination. Comprehensive structural, spectroscopic, and computational analyses suggest that the intermolecular hydrogen-bonding environment is associated with the relative contributions of intraligand charge-transfer (3ILCT) and metal/halide-to-ligand charge-transfer (3(M + X)LCT) excited states. Compound 2, which features weaker intermolecular interactions, shows a much weaker 3ILCT contribution together with highly efficient 3(M + X)LCT emission and a near-unity photoluminescence quantum yield of 98.5%. The compound further demonstrates efficient radioluminescence and robust stability, highlighting its potential as an X-ray scintillator. This work suggests that intermolecular interactions may play an important role in tuning excited-state dynamics in copper(I) halide hybrid materials.