Chemical reactions of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) with metallic copper, silver, and mercury

Chemical reactions of DMTD with metallic copper, silver, and mercury have b een studied by infrared (IR), surface-enhanced Raman scattering (SERS), UV- vis, and X-ray photoelectron spectrum (XPS) techniques. It is found that DM TD can react readily with metallic copper, silver, and mercury under mild c onditions. The reaction product of DMTD with metallic copper shows an IR sp ectrum slightly different from that of Cu(DMTD)(2), suggesting a Cu+ compon ent in the product, which is further confirmed by the XPS result. The react ion products of DMTD with metallic silver and liquid mercury are Ag(DMTD) a nd Hg(DMTD)(2), respectively. A two-step mechanism is proposed for these su rface reactions: first DMTD is chemisorbed on the metal surfaces with the f ormation of the disulfide salt of DMTD as the intermediate product, and the n the unstable disulfide salt reacts further with the excessive DMTD in sol ution, forming the monosulfide salt of DMTD which covers the metal surfaces in the form of a polymer layer or even a monolayer.