Synthesis, Photophysics, Electrochemistry, Theoretical, and Transient Absorption Studies of Luminescent Copper(I) and Silver(I) Diynyl Complexes. X-ray Crystal Structures of [Cu 3 (μ-dppm) 3 (μ 3 -η 1 -C⋮CC⋮CPh) 2 ]PF 6 and [Cu 3 (μ-dppm) 3 (μ 3 -η 1 -C⋮CC⋮CH) 2 ]PF 6