Phosphorescent properties of metal-free diphosphine ligands and effects of copper bindingElectronic supplementary information (ESI) available: Spectroscopic analysis, and the CIF files for compounds 1-4. CCDC 939002-939005. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3dt51390d

We studied the luminescence properties of copper( i ) complexes containing bis[2-(diphenylphosphino)phenyl]ether (DPEphos), [Cu(DPEphos)(CH 3 CN)]PF 6 ( 1 ), [Cu(DPEphos) 2 ]PF 6 ( 2 ), and copper( i ) complexes with 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos), [Cu(xantphos)(CH 3 CN) 2 ]PF 6 ( 3 ), [Cu(xantphos) 2 ]PF 6 ( 4 ) in the solid state. The metal-free xantphos ligand shows weak phosphorescent emission at around 455 nm with an emission lifetime in the sub-microsecond range in the solid state at room temperature. When xantphos forms complex 4 , it results in a nearly 4-fold increase in the emission quantum yield and emission lifetime, with a small shift in the emission maximum. In contrast, no such enhancement in the luminescence or increment in the emission lifetime was observed in complexes 1-3 . The X-ray structural analysis of complexes 1-4 reveals a large vacant space in complexes 1-3 and in contrast, close packing of the ligands in complex 4 around the metal center. This indicates that the decrease in the free-space around the metal center results in a decrease in the geometric relaxation, suppressing the excited-state deactivation pathway. We studied the luminescence properties of copper( i ) complexes containing bis[2-(diphenylphosphino)phenyl]ether (DPEphos), [Cu(DPEphos)(CH 3 CN)]PF 6 ( 1 ), [Cu(DPEphos) 2 ]PF 6 ( 2 ), and copper( i ) complexes with 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos), [Cu(xantphos)(CH 3 CN) 2 ]PF 6 ( 3 ), [Cu(xantphos) 2 ]PF 6 ( 4 ) in the solid state.