Synthesis, structures and photophysical properties of polynuclear copper(I) iodide complexes containing phosphine and 4,4′-bipyridine ligands

The highly luminescent polynuclear CuI iodide complexes, [(Cu2I2)(4,4′-bipy)(PCy3)2]2 · 4H2O (1), [(Cu2I2)(4,4′-bipy)(PCy3)2]∞ (2), [(Cu2I2)(4,4′-bipy)(dcpm)]∞ (3) and [(Cu2I2)(4,4′-bipy)(dppm)]∞ (4), were prepared by reacting CuI with tricyclohexylphosphine (PCy3), bis(dicyclohexylphosphino)methane (dcpm) or bis(diphenylphosphino)methane (dppm) and 4,4′-bipyridine (4,4′-bipy), and their structures were determined by X-ray crystal analysis. The reported complexes [CuClPCy3]2 (5) and [CuIPCy3]2 (6) were also prepared for comparison. In solid state, complexes 1–6 display intense long-lived phosphorescence with λmax at 605, 565, 640, 570, 430 and 450 nm at room temperature, and the solid-state emission quantum yields are 0.11, 0.20, 0.29, 0.35, 0.67 and 0.83, respectively. The relatively high-energy emissions of 5 and 6 are attributed to arising from metal-centered MC (3d → 4s, 4p) excited state, while the low-energy emissions of 1–4 are assigned to a metal-to-ligand charge transfer (d → π∗ MLCT) excited state.

Graphical abstractNew polynuclear CuI iodide complexes containing bulky phosphine and 4,4′-bipyridine ligands were prepared, whose crystal structures and spectroscopic properties have been investigated. The results on phosphorescent emission spectra and density functional theory calculation show that MC (3d → 4s, 4p) and MLCT (5p/3d → π∗bipy) parentages may be involved in these complexes.Figure optionsDownload full-size imageDownload as PowerPoint slide