Utilization of a Nonemissive Triphosphine Ligand to Construct a Luminescent Gold(I)-Box That Undergoes Mechanochromic Collapse into a Helical Complex

Luminescent gold­(I) complexes ([Au₆(Triphos)₄Cl]­(PF₆)₅·2­(CH₃C₆H₅), [Au₆(Triphos)₄Cl]­(AsF₆)₅·8­(CH₃C₆H₅), and [Au₆(Triphos)₄Cl]­(SbF₆)₅·7­(CH₃C₆H₅) where Triphos = bis­(2-diphenylphosphinoethyl)­phenylphosphine) with a boxlike architecture have been prepared and crystallographically characterized. A chloride ion resides at the center of the box with two of the six gold­(I) ions nearby. Mechanical grinding of blue luminescent crystals containing the cation, [Au₆(Triphos)₄Cl]⁵⁺, results in their conversion into amorphous solids with green emission that contain the bridged helicate cation, [μ-Cl­{Au₃(Triphos)₂}₂]⁵⁺. A mechanism of the mechanochromic transformation is proposed. The structures of the blue-emitting helicate, [Au₃(Triphos)₂]­(CF₃SO₃)₃·4­(CH₃C₆H₅)·H₂O, and the green-emitting bridged-helicate, [μ-Cl­{Au₃(Triphos)₂}₂]­(PF₆)₅·3CH₃OH have been determined by single crystal X-ray diffraction.