Adsorbed thiolates

Wang ZLetal 1998 Bundling and interdigitation of adsorbed thiolate groups in self-assembled nanoorystal superlattioes J. Phys. Chem. B 102 3068... 

The initial step of the adsorption of thiols on a Mo(100) surface is the formation of adsorbed thiolate groups. Phenyl thiolate is formed upon adsorption of thiophenol at 120 K on a clean Mo(110) surface.381 The thiolate intermediate subsequently undergoes competing C-S bond hydrogenolysis to form benzene, or C-S and C-H bond scission to form surface benzyne. The adsorption of thiophenol was also studied on a sulfur-covered Mo surface382 Phenyl disulfide is formed via S-H bond scission and S-S bond formation. The S-S linkage is oriented perpendicular and the phenyl ring parallel to the surface. 

The initial step of the adsorption of cyclic sulfides on a Mo(100) surface is also the formation of adsorbed thiolate groups.395-397 Adsorbed alkyl thiolates decompose to adsorbed sulfur, carbon, and hydrogen on the clean Mo surface, but once the surface is deactivated by adsorbed sulfur, alkanes and alkenes evolve from the surface. Tetrahydrothiophene (34) and trimethylene sulfide decompose on Mo(110) to alkanes and alkenes by way of a common intermediate, which is proposed to be a surface thiolate (33). The thiolate undergoes hydrogenation or dehydrogenation, depending on the surface hydrogen concentration (Scheme 4.115).398 399... 

Imabayashi S, Hobara D, Kakiuchi T (2001) Voltammetric detection of the surface diffusion of adsorbed thiolate molecules in artificially phase-separated binary self-assembled monolayers on a Au(lll) surface. Langmuir 17 2560-2563... 

The island mechanism assumes that adsorption takes place in wet conditions and H2O adsorbed on the carbon surface, is able to create water clusters or small water islands, where MM and oxygen first are dissolved in molecular form and later, depending on the pH, MM can dissociate to thiolate ion. Oxidation occurs due to the surface reaction between adsorbed thiolate ions and dissodatively adsorbed oxygen in water "islands" and/or between adsorbed MM and oxygen on a dry part of the carbon surfece. The product of reaction, DMDS, is adsorbed in a molecular form on the carbon surface (Fig. 35). 

The reductive desorption is initiated by a one-electron reduction of adsorbed thiolates followed by the desorption of reduced species, alkanethiolates, from the surface [1, 88]. 

Another important point in Fig. 6(a) is that the present model explains why the FWHM levels off beyond n = 9. When the attractive interaction is strong enough to cause the phase transition in the adsorbed monolayer, the shape of the adsorption isotherm, or more precisely, the sharpness of the phase transition becomes insensitive to the value of gi when g2 > (curves 1-3, Fig. 5) [95]. In other words, the appearance of the point of inflection suggests the occurrence of the phase transition in the course of the desorption. The critical value of w at the point of inflection corresponds to 2.7 kj mol at 25 °C. This value reflects not only the magnitude of the lateral interaction between two adsorbed thiolate molecules but also other contributions including those from solvent molecules [95]. 

The phase separation of thiol SAMs observed experimentally is in quasi-equihbrium in nature. Unlike the phase separation of binary solutions, the mutual solubiKty of the adsorbed thiolates depends on the composition, =... 

SAMs of TDT and MPOH at three total concentrations of TDT and MPOH in ethanol. The variation of the mutual solubility with X poH i probably due to the slow surface diffusion of adsorbed thiolates. The slope of X h orption of MPOH-rich domains increases with the increase in the total concentration of the thiols in the bathing solution the smaller the domain, the larger the slope is. The slope and its concentration dependence are much smaller for the reduction of TDT-rich domains. 

Rate of the Replacement of Adsorbed Thiolates with Thiols in the Solution Phase... 

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