Mechanochemical preparation of copper iodide clusters of interest for luminescent devices

Abstract

The copper iodide complexes are known for their large variety of coordination geometries. Such diversity, while making it difficult to predict the final structure, permits the preparation of a great number of copper iodide complexes based on the same ligand. The target of the research was that of thoroughly exploring the chemistry of CuI and the ligand diphenyl-2-pyridyl phosphine (PN) by varying the stoichiometric ratio and/or the aggregation state. Six different compounds have been identified: [Cu₄I₄(PN)₂], [Cu₄I₄(PN)₂·(CH₂Cl₂)_0.5], [CuI(PN)_0.5]_∞, [CuI(PN)₃] whose structures have been determined during this study, CuI(PN)₂ which was characterized by powder diffraction and [Cu₂I₂(PN)₃] which has been already reported. The preparation routes are also different: synthesis in solution yielded [Cu₄I₄(PN)₂·(CH₂Cl₂)_0.5] and [CuI(PN)₃] while [CuI(PN)_0.5]_∞ and CuI(PN)₂ were obtained only via solid state reactions. These two latter examples confirmed that mechanochemistry is a valid route to explore the landscape of the possible structures of CuI derivatives. Crystallization by traditional solution procedures failed to give the desired crystal, so structure determination of the new compounds was tackled in two ways: by attempting crystal growth via solvothermal synthesis and by resolving the structure from X-ray powder diffraction data with “direct space” methods. What is more the photophysical properties of the complexes that could be obtained as sufficiently pure powders have also been investigated and are reported herein.