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 ([Au 6 (Triphos) 4 Cl](PF 6 ) 5 ·2(CH 3 C 6 H 5 ), [Au 6 (Triphos) 4 Cl](AsF 6 ) 5 ·8(CH 3 C 6 H 5 ), and [Au 6 (Triphos) 4 Cl](SbF 6 ) 5 ·7(CH 3 C 6 H 5 ) 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, [Au 6 (Triphos) 4 Cl] 5+, results in their conversion into amorphous solids with green emission that contain the bridged helicate cation, [μ-Cl{Au 3 (Triphos) 2 } 2 ] 5+ . A mechanism of the mechanochromic transformation is proposed. The structures of the blue-emitting helicate, [Au 3 (Triphos) 2 ](CF 3 SO 3 ) 3 ·4(CH 3 C 6 H 5 )·H 2 O, and the green-emitting bridged-helicate, [μ-Cl{Au 3 (Triphos) 2 } 2 ](PF 6 ) 5 ·3CH 3 OH have been determined by single crystal X-ray diffraction.