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(μ3-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 3CC excited state with mixed 3XMCT character.