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The complex [Cu4(tu)7](SO4)2·H2O was isolated by addition of thiourea to a copper(II) sulfate electrolyte solution consisting of 2 M H2SO4 and 0.7 M CuSO4. The crystal structure of this complex was solved by X-ray methods and highlighted a [Cu4(tu)7]4+ adamantane cluster. A copper(I)−thiourea cluster of this stoichiometry has not been previously reported. The X-ray structure is refined to residual R = 0.0447 for 4093 observed reflections. Crystals are orthorhombic, of space group Pbca, with Z = 8 in a cell of dimensions a = 10.414(3), b = 17.909(3), and c = 35.818(3) Å. The copper atoms lie in a tetrahedral arrangement in which one of the copper atoms is four-coordinate, while the other three display trigonal planar coordination with Cu···Cu distances of 2.899(2)−2.967(2)Å. The copper−thiourea clusters are interlinked by sulfate ions, which strongly interact with the thiourea ligands through hydrogen bonds. The infrared and Raman spectra of the title compound and of the related copper(I) thiourea complexes [Cu2(tu)5](SO4)·3H2O, [Cu2(tu)6](SO4)·H2O, [Cu4(tu)6](NO3)4·4H2O, and [Cu4(tu)9](NO3)4·4H2O were recorded and assigned, and the dependence of ν(CuS) on the coordination environment of the copper was established.

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Surface-enhanced Raman scattering (SERS) spectroscopy has been applied to identify species formed during gold leaching in thiosulfate media. Surface coverages of copper and sulfur for various thiosulfate dissolution systems were determined electrochemically and by X-ray photoelectron spectroscopy. A gold sulfide monolayer was shown to be formed slowly in the potential region where leaching occurs. At higher potentials, more sulfur is adsorbed but, rather than creating a multilayer, sulfur-sulfur linkages are formed with the sulfur atoms no longer being covalently bonded to gold. SERS spectra show the presence of polythionates on the gold surface in addition to gold sulfide and S0 . At longer exposure times, thiosulfate is oxidized to elemental sulfur and sulfate, both products being identified by normal Raman spectroscopy from the leach solution. In typical thiosulfate/ammonia/copper(II) leach solutions, copper is present on the surface of gold in addition to sulfur. In these situations, ammonia is coadsorbed.