Self-Assembly of Gold(I) Compounds with (Aza-15-crown-5)dithiocarbamate and 2-Mercapto-4-methyl-5-thiazoleacetic Acid

Treatment of AuCl(SMe2) with equimolar sodium (aza-15-crown-5)dithiocarbamate (O4NCS2) or
2-mercapto-4-methyl-5-thiazoleacetic acid (HSSCOOH) in the presence of NaOMe affords a dinuclear complex, [Au(O4NCS2)]2 1, and a tetranuclear complex, [Au(SSCOOH)]4 2, respectively. 1 features a dinuclear structure containing
two azacrown ether rings, and there is a short intramolecular gold(I)···gold(I) distance of 2.7820(5) Å. Importantly,
2 crystallizes in two forms: 2·4THF and 2·4DMF, where the solvent molecules are hydrogen-bonded to the carboxylic
acid moiety of SSCOOH. 2·4THF and 2·4DMF are tetranuclear complexes featuring an interesting double-clipped
structure built from both thiazole rings and carboxylic acid moieties. The four gold(I) centers in 2 form a pucker-squared channel with four equivalent gold(I)···gold(I) distances of 3.0478(4) Å for 2·4THF and 3.0423(4) Å for 2·4DMF, respectively, and this one-dimensional channel structure may be rationalized by π···π interactions and/or
weak intermolecular Au···S interactions of 3.800 Å for 2·4THF or 3.986 Å for 2·4DMF, respectively. Interestingly,
with the same synthetic strategy 1 and 2 are formed with different nuclearities. This dramatic different structural
motif between 1 and 2 may be ascribed to crystal packing of azacrown ether rings in part. At room temperature, 2
shows low-energy dual emissions with maxima at 585 and 720 nm, whereas it shows only a strong emission with a
maximum at 585 nm at 77 K. This interesting luminescence property is suggested to be closely related to aurophilic
interactions.