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

A number of neutral unsymmetrical dimers [(Ph3P)(2)Cu(mu-SeC{O}R)(2)Cu(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 P-31 NMR. Variable temperature P-31 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-C6H4C=O groups have anti stereochemistry with respect to the Cu2Se2 ring while MeC=O groups have syn configuration in 6. A weak C-H...O=C 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 Cu2-xSe nanoparticles with an average size of 75 +/- 15 nm.