Supramolecular Assembly, Solvent-Induced, and Mechanochromic Luminescence of Au(I) Quinoline-8-thiolates.

AuCl(PMe) and AuCl(PEt) were used to react with quinoline-8-thiolate (8-QNS) to give three Au(I) complexes, i.e., [8-QNS(AuPMe)]ClO (), [(8-QNS)Ag(AuPMe)]ClO (), and [8-QNS(AuPEt)]ClO (), which have been structurally determined by X-ray diffraction to show various intra- and intermolecular metal···metal contacts (i.e., metal = Au(I) or Ag(I)). All complexes displayed solid-state luminescence at 535-568 nm, which is most likely attributed to an intraligand transition of 8-QNS and/or a S → Au(I) charge-transfer transition, possibly modified by Au(I)···Au(I) interactions. Notably, complex ·CHCl exhibited remarkable mechanochromic luminescence from 535 to 601 nm upon grinding. While immersed in various solvents for the ground powder samples of complex ·CHCl, the luminescence at 601 nm mostly reverted to the original luminescence. Powder X-ray diffraction measurements indicated that complex ·CHCl underwent structural transformation from a crystalline to an amorphous phase upon grinding, and it can be restored to the original crystalline phase upon immersion in various solvents. Additionally, the reversible experiments of complex ·CHCl for the grinding and immersion actions were performed for up to five cycles. Moreover, the time-dependent luminescence spectra for the crystalline samples of complex ·CHCl were measured, and they showed a significant luminescence change from 535 to 590 nm within 2 days.