Cubane Copper(I) Iodide Clusters with Remotely Functionalized Phosphine Ligands: Synthesis, Structural Characterization and Optical Properties

We present here the synthesis, chemical, and photophysical study of a series of three new copper halide derivatives, namely 2a-c. They are all tetranuclear copper-iodide clusters of general formula [Cu(& mu;(3)-I)P](4) consisting of a cubane-like {Cu4I4} motif and P = phosphine. They differ in the type of the phosphines used as ligands: a monophosphine with a single pendant ester unit (complex 2a), two pendant ester units (2b), and a diphosphine containing two esters in the linker (2c). The molecular structure of the complexes was determined by single-crystal X-ray diffraction analysis. All the investigated derivatives were found to be photo- and thermally-stable luminescent species. In the solid state, the complexes display intense and long-lived photoluminescence in the orange region with PLQY values of 0.43-0.84 at room temperature associated mainly with a (CC)-C-3 excited state with mixed (XMCT)-X-3 character.