Chemical Reactions of 2,5-Dimercapto-1,3,4-thiadiazole (DMTD) with Metallic Copper, Silver, and Mercury

Abstract

Chemical reactions of DMTD with metallic copper, silver, and mercury have been studied by infrared (IR), surface-enhanced Raman scattering (SERS), UV-vis, and X-ray photoelectron spectrum (XPS) techniques. It is found that DMTD can react readily with metallic copper, silver, and mercury under mild conditions. The reaction product of DMTD with metallic copper shows an IR spectrum slightly different from that of Cu-(DMTD) 2 , suggesting a Cu + component in the product, which is further confirmed by the XPS result. The reaction products of DMTD with metallic silver and liquid mercury are Ag(DMTD) and Hg(DMTD) 2 , respectively. A two-step mechanism is proposed for these surface reactions: first DMTD is chemisorbed on the metal surfaces with the formation of the disulfide salt of DMTD as the intermediate product, and then the unstable disulfide salt reacts further with the excessive DMTD in solution, forming the monosulfide salt of DMTD which covers the metal surfaces in the form of a polymer layer or even a monolayer.

Ultrasensitive and selective spectrofluorimetric determination of Hg(II) using a dimercaptothiadiazole fluorophore

“…1a. It shows a predominant band at 330 nm with a shoulder band at 257 nm, corresponding to dithiol and thiolate forms of DMT, respectively [27,28]. of Hg(II).…”

“…It clearly suggests that DMT makes a complex with Hg(II) [27,28,30]. Job's method was applied to find the stoichiometric composition of the complex formed between Hg(II) and DMT and was found to be 1:2 ( Fig.…”

“…2,5-Dimercpato-1,3,4-thiadiazole (DMT) is an interesting ligand having five donor atoms in protonated and deprotonated forms and it has been extensively used as a chelating ligand [27][28][29]. In the solid state, DMT exists as a thiolate tautomer, while in solution it exists as dithiol, thiolate and dithione forms and solvent dependent equilibrium obtained between all forms (Scheme 1).…”

“…In the solid state, DMT exists as a thiolate tautomer, while in solution it exists as dithiol, thiolate and dithione forms and solvent dependent equilibrium obtained between all forms (Scheme 1). It has acid dissociation constants of pK a 1 ¼ À1.36 and pK a 2 ¼7.5, making its neutral form a very strong acid and its anionic form a weak acid [28,30,31]. DMT has four donor sites, and it can coordinate with either (a) both the nitrogen atoms, or (b) both the thiocarbonyl sulfur atoms or (c) one nitrogen atom and one sulfur atom on either the same side or different sides of the molecule.…”

“…DMT has four donor sites, and it can coordinate with either (a) both the nitrogen atoms, or (b) both the thiocarbonyl sulfur atoms or (c) one nitrogen atom and one sulfur atom on either the same side or different sides of the molecule. The p-electron in the aromatic heterocyclic ring can also coordinate with metal ions [28,31]. These interesting coordinating properties of DMT induced us to use it as a fluorophore in the present study to determine Hg(II) by spectrofluorimetric method.…”