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.