Ligand Engineering of Copper(I) Iodide Coordination Polymers: Regulating Coordination Environment, Molecular Packing, and X-ray Scintillation Performance

Three copper(I) iodide coordination polymers (CPs), Cu 2 I 2 (bpp)(PPh 3 ) 2 ( 1, bpp = 1,3-dipyridylpropane, PPh 3 = triphenylphosphine), Cu 2 I 2 (bpp)(PPh 2 (Tol)) 2 ( 2, PPh 2 (Tol) = diphenyl- p -tolylphosphine), and Cu 2 I 2 (bpp)(P(Tol) 3 ) 2 ( 3, P(Tol) 3 = tri- p -tolylphosphine), were synthesized from 1,3-dipyridylpropane as the bridging ligand and triphenylphosphine and its methyl-substituted derivatives as terminal ligands for high-performance X-ray scintillation. Single-crystal X-ray diffraction analysis revealed that monomethyl substitution in CP 2 maintains isostructural chain connectivity with CP 1, but significantly enhances the compactness of molecular packing. Further increasing methyl substituents led to distinct chain connectivity in CP 3 . All three CPs exhibited room-temperature thermally activated delayed fluorescence with high photoluminescence quantum yields of 91%, 99%, and 88% for 1, 2, and 3 . Benefiting from the strong X-ray absorption of heavy Cu and I atoms and high luminescence efficiency, all three CPs show outstanding X-ray scintillation performance, with XEL intensities 5.4, 7.6, and 5.9 times that of the commercial BGO scintillator, respectively. The optimal CP 2 exhibits a low detection limit of 20.4 nGy/s and a high spatial resolution of 20 lp mm –1 in X-ray imaging, demonstrating its great potential application in X-ray imaging. This work provides a facile ligand engineering strategy to regulate the crystal structure and packing of copper(I) iodide CPs, offering valuable design insights for developing high-performance scintillation materials.