Photophysical properties have been studied for a series of luminescent copper (I) halide complexes,[Cu (μ-X) dppb] 2 and CuI (dppb)(PPh3). The emission in the solid states originates from an (M+ X) LCT excited state, in which the two emissive excited states, S1 and T1, are equilibrated with an energy difference of 1-2 kcal/mol. In the excited state, the complex in the solid state and in the solution takes favorable geometry: distorted ...