Cuprophilic Interactions in Luminescent Copper( I ) Clusters with Bridging Bis(dicyclohexylphosphino)methane and Iodide Ligands: Spectroscopic and Structural Investigations

Polynuclear copper( I ) complexes with bridging bis(dicyclohexylphosphino)methane (dcpm) and iodide ligands, [Cu 2 (dcpm) 2 (CH 3 CN) 2 ](BF 4 ) 2 ( 1 ), [Cu 2 (dcpm) 2 ](BF 4 ) 2 ( 2 ), [(CuI) 3 (dcpm) 2 ] ( 3 ), [(CuI) 4 (dcpm) 2 ] ( 4 ), and [(CuI) 2 (dcpm) 2 ] ( 5 ) were prepared and their structures determined by X‐ray crystal analysis. The shortest CuCu distance found in these complexes is 2.475(1) Å for 3 . Powdered samples of 1 , 3 , 4 , and 5 display intense and long‐lived phosphorescence with λ max at 460, 626, 590, and 456 nm and emission quantum yields of 0.26, 0.11, 0.12, and 0.56 at room temperature, respectively. In the solid state, 2 displays both a weak emission at 377 and an intense one at 474 nm with an overall emission yield 0.42. The difference in emission properties among complexes 1 – 5 suggests that both CuCu interaction and coordination around the copper( I ) center affect the excited state properties. A degassed solution of 2 in acetone gives a bright red emission with λ max at 625 nm at room temperature. The difference absorption spectra of the triplet excited states of 1 – 5 in acetonitrile show broad absorption peaks at 340–410 and 850–870 nm.