Emission Modulation in NHT-Based Dinuclear Copper(I) Iodide Complexes by N -Aryl Substituents

We demonstrate that N-aryl substituents tuned the photoluminescence behavior of dinuclear copper(I) iodide complexes, [Cu2I2(L1)2] (1), [Cu2I2(L2)2] (2), and [Cu2I2(L3)2] (3), synthesized by reacting CuI with the corresponding ligands: L1 = (1-(2,6-diisopropylphenyl)-3-(pyridin-2-yl)-imidazole-2-thione, L2 = 1-(2-isopropylphenyl)-3-(pyridin-2-yl)-imidazole-2-thione, and L3 = 1-(2-phenyl)-3-(pyridin-2-yl)-imidazole-2-thione. The complexes were characterized by FT-IR, PXRD, UV–vis, TGA, and fluorescence spectroscopy techniques. Single-crystal analysis revealed that 1–3 adopt a distorted tetrahedral geometry around the copper(I) centers, with a rhomboid Cu2I2 cluster core. In the crystalline state, they emit in the green-to-yellow regions. Complexes 1 and 2 exhibit high photoluminescence quantum yields (65 and 60%) and long average lifetimes (16.23 and 13.64 μs), whereas complex 3 shows a lower efficiency (4%, 2.86 μs). Prototype LED bulbs coated with 1–3 demonstrated their potential for light-emitting performance.