Supramolecular\nAssembly, Solvent-Induced, and Mechanochromic\nLuminescence of Au(I) Quinoline-8-thiolates

AuCl(PMe<sub>3</sub>) and AuCl(PEt<sub>3</sub>) were\nused to react\nwith quinoline-8-thiolate (8-QNS) to give three Au(I) complexes, i.e.,\n[8-QNS(AuPMe<sub>3</sub>)<sub>2</sub>]ClO<sub>4</sub> (<b>1</b>), [(8-QNS)<sub>2</sub>Ag­(AuPMe<sub>3</sub>)<sub>2</sub>]ClO<sub>4</sub> (<b>2</b>), and [8-QNS­(AuPEt<sub>3</sub>)<sub>2</sub>]ClO<sub>4</sub> (<b>3</b>), which have been structurally\ndetermined by X-ray diffraction to show various intra- and intermolecular\nmetal···metal contacts (i.e., metal = Au(I) or Ag(I)).\nAll complexes displayed solid-state luminescence at 535–568\nnm, which is most likely attributed to an intraligand transition of\n8-QNS and/or a S → Au(I) charge-transfer transition, possibly\nmodified by Au(I)···Au(I) interactions. Notably, complex <b>1</b>·CH<sub>2</sub>Cl<sub>2</sub> exhibited remarkable mechanochromic\nluminescence from 535 to 601 nm upon grinding. While immersed in various\nsolvents for the ground powder samples of complex <b>1</b>·CH<sub>2</sub>Cl<sub>2</sub>, the luminescence at 601 nm mostly reverted\nto the original luminescence. Powder X-ray diffraction measurements\nindicated that complex <b>1</b>·CH<sub>2</sub>Cl<sub>2</sub> underwent structural transformation from a crystalline to an amorphous\nphase upon grinding, and it can be restored to the original crystalline\nphase upon immersion in various solvents. Additionally, the reversible\nexperiments of complex <b>1</b>·CH<sub>2</sub>Cl<sub>2</sub> for the grinding and immersion actions were performed for up to\nfive cycles. Moreover, the time-dependent luminescence spectra for\nthe crystalline samples of complex <b>1</b>·CH<sub>2</sub>Cl<sub>2</sub> were measured, and they showed a significant luminescence\nchange from 535 to 590 nm within 2 days.