Synthesis, structural characterization, photoluminescence and thermal properties of [(Ph3P)2Cu(μ-SeC{O}R)2Cu(PPh3)]

Abstract

A number of neutral unsymmetrical dimers [(Ph₃P)₂Cu(μ-SeC{O}R)₂Cu(PPh₃)] (R = C₆H₅ (1), C₆H₄-Me-4 (2), C₆H₄-OMe-4 (3), C₆H₄-Cl-4 (4), C₆H₄-F-4 (5) and CH₃ (6)) were synthesized in moderate yield, and characterized by analytical and spectroscopic techniques including ³¹P NMR. Variable temperature ³¹P NMR experiments appear to indicate that the molecular structure is retained in solution. X-Ray structure determination of 2 and 6 confirmed the molecular geometry of the unsymmetrical dimer. In 2 the two 4-MeO-C₆H₄CO groups have anti stereochemistry with respect to the Cu₂Se₂ ring while MeCO groups have syn configuration in 6. A weak C–H⋯OC intramolecular hydrogen bond present between the two selenoacetato ligands appears to dictate the syn geometry in 6. This hydrogen bonding is also responsible for the non-planarity of the Cu₂Se₂ ring. These compounds are photoemissive in CH₂Cl₂ solution. Thermogravimetry and pyrolysis experiments in nitrogen atmosphere show that 1–6 are good single source precursors to copper selenide bulk materials. Preliminary experiments show that these compounds are good single source molecular precursors for cubic phase Cu_2−xSe nanoparticles with an average size of 75 ± 15 nm.