Copper(i) iodide complexes based on [Cu5I7]2− units and cationic organic ligands for X-ray scintillation and imaging

Abstract

Copper(I) iodide complexes represent a kind of promising scintillator due to their high luminescence efficiency, low toxicity, cost-effectiveness, and high atomic number of iodine, which enhances X-ray absorption. Herein, we report two copper(I) iodide complexes, Cu₅I₇(Ted-Pre)₂ (1) and Cu₅I₇(Ted-EA)₂ (2), constructed from anionic [Cu₅I₇]²⁻ cluster units and cationic organic ligands derived from triethylenediamine (Ted). Structural analysis revealed distinct bridging modes of iodide anions within the [Cu₅I₇]²⁻ cluster units. Complex 1 contained a rare μ₅-bridging iodide that enhanced the structural rigidity for the [Cu₅I₇]²⁻ unit, which should correlate with its superior photoluminescence quantum yield (72.8%) and improved thermal stability compared to complex 2. Under X-ray excitation, 1 achieved a light yield of 19 010 photons per MeV, surpassing that of the commercial scintillator Bi₄Ge₃O₁₂ (BGO, 10 000 photons per MeV), along with a detection limit of 88.5 nGy s⁻¹, well below the typical medical imaging threshold. When incorporated into a flexible polydimethylsiloxane film, 1 achieved a spatial resolution of 8 lp mm⁻¹ in X-ray imaging. These results highlight the potential of structurally tailored copper(I) iodide complexes as efficient and cost-effective scintillators for advanced X-ray imaging applications.