Near-unity room-temperature phosphorescence quantum yield induced by halogen–halogen interaction in chiral hybrid copper(i) iodide clusters†

Employing chiral (R/S)-4-chloro/bromo-α-methylbenzylamine (R/S-X-MBA, X = Cl, Br) as ligands, we prepare two zero-dimensional hybrid copper(I) iodide clusters, (R/S-Cl-MBA)₄Cu₄I₄ (R/S-Cl) and (R/S-Br-MBA)₄Cu₄I₄ (R/S-Br), via a simple room-temperature solvent-diffusion method. Both R/S-Cl and R/S-Br are in the C2 chiral space group with a monoclinic crystal system. Under 310 nm excitation, R/S-Cl and R/S-Br exhibit efficient orange and yellow broadband luminescence, featuring large Stokes shifts, microsecond lifetimes, and symmetric chiral CD signals. Interestingly, compared to R/S-Cl with a photoluminescence (PL) quantum yield (QY) of ∼46%, a near-unity PLQY is observed for R/S-Br, along with a longer PL lifetime (∼13.5 μs). The high PLQY is attributed to intermolecular halogen–halogen interactions, which greatly enhance lattice rigidity and suppress nonradiative recombination of triplet excitons. Furthermore, R/S-Br has been demonstrated for X-ray scintillator application. This work offers an effective strategy for designing multifunctional and efficient chiral phosphors.