Photoreactivity of (2,9-dimethyl-1,10-phenanthroline) copper(I) borohydride

The complex (dmp)CuI(BH4) with dmp=2,9-dimethyl-1,10-phenanthroline displays a long-wavelength absorption at λmax=465 nm which is assigned to a BH4−→dmp ligand-to-ligand charge transfer (LLCT) transition. In the solid state the LLCT state is emissive (λmax=626 nm). In non-coordinating solvents such as CH2Cl2,CHCl3 or toluene the complex undergoes a photoredox decomposition leading to the generation of metallic copper. At λirr=436 nm (dmp)CuI(BH4) disappears with φ=1.2×10−3.