The electrochemical behavior of a nonanethiol layer adsorbed on Au(111), Au(110), and on a Au polycrystal has been examined using cyclic voltammetry. The reductive desorption and the oxidative redeposition of the nonanethiol molecules at the Au(111) surface have been shown to depend strongly on the pH of the electrolyte solutions. While the amount of material reductively desorbed from the surface on the first cathodic cycle is independent of the pH, the amount of material that is oxidatively redeposited increases significantly as the pH is lowered. This behavior is ascribed to a reduction in solubility of the product of desorption (thiolate or thiol) as pH decreases. At high pH the redeposition of the layer seems to occur in one step, but at pH values that are lower than the pK a of the nonanethiol the redeposition seems to occur in two steps. In an alkaline solution, the reductive desorption of the nonanethiols from a Au(110) surface is similar to the same process at the Au(111) surface. The double layer charging current, the shape of the reductive current peak, and its integrated charge are similar to those measured on the Au(111) electrode. Our single crystals study also reveals a correlation between the potential of zero charge of the uncoated gold single crystal electrodes and the potential at which the reductive desorption of the nonanethiols occurs. The results on a polycrystalline surface indicate a complex stripping pattern that is related to the different crystallographic domains present on the polycrystalline electrode.

The electrochemistry of a hexadecanethiol monolayer deposited on a Au(111) single crystal electrode has been examined in electrolyte solutions of different pH values, and it has been found that a significant fraction of the hexadecanethiol monolayer can be electrochemically removed and redeposited repetitively from the Au(111) surface. We suggest that this behavior is caused by the low solubility of the reduced molecules which prevents their diffusion into the bulk of the solution. The solubility of the thiol is confirmed to be a most important factor in the oxidative redeposition process by identical experiments performed on butanethiol and nonanethiol layers which show a decrease in the oxidative redeposition with the increasing solubility of the thiol. Preliminary work suggests that surface roughness may also play a part in influencing the extent of oxidative redeposition, with smoother surfaces giving more redeposition. The reductive desorption/oxidative redeposition of hexadecanethiols in an aqueous solution of high pH (0.5 M KOH) consists of two distinct processes. This is suggested to arise from the presence of domains of thiols of different ionic permeabilities.

We describe a novel corticotropin-releasing factor receptor 1 (CRF 1 ) antagonist with advantageous properties for clinical development, and its in vivo activity in preclinical alcoholism models. 1-10 mg/kg). In contrast, MTIP dose-dependently reversed anxiogenic effects of withdrawal from a 3 g/kg alcohol dose. Similarly, MTIP blocked excessive alcohol self-administration in Wistar rats with a history of dependence, and in a genetic model of high alcohol preference, the msP rat, at doses that had no effect in nondependent Wistar rats. Also, MTIP blocked reinstatement of stress-induced alcohol seeking both in postdependent and in genetically selected msP animals, again at doses that were ineffective in nondependent Wistar rats. Based on these findings, MTIP is a promising candidate for treatment of alcohol dependence.

Vibrational energy relaxation of the internal C–O stretching mode of carbon monoxide in the c(2×2) overlayer on the Cu(100) surface at 120 K is measured by picosecond pump–probe spectroscopy. A resonant 1.5 ps infrared pulse at ν=2085 cm−1 pumps the C–O stretching mode. The energy relaxation is monitored by sum frequency generation from a delayed pair of 1.5 ps infrared and visible pulses. A single component decay, with a decay time of 2.0 ±0.5 ps, is reported. Uncertainties in the actual excited state lifetime are discussed, and the actual lifetime is estimated to be 2.0 ±1.0 ps. This lifetime is close to the lower limit of 1.2 ps set by the observed vibrational linewidth of 4.5 cm−1. The energy relaxation process is interpreted to occur by nonadiabatic energy transfer to the electrons (electron-hole pair excitations) of the copper substrate, and the measurement supports previous assertions that the nonadiabatic energy transfer rate for this system is very rapid. The nonadiabatic energy transfer lifetime of this mode has previously been estimated by density-functional calculations [T. T. Rantala and A. Rosen, Phys. Rev. B 34, 837 (1986)], and has recently been calculated by extrapolation of ab initio Hartree–Fock electronic structure calculations for CO on copper clusters [M. Head-Gordon and J. Tully, preceding paper, J. Chem. Phys. 96, 3939 (1992)]. The calculated lifetimes in both cases are in the 1–3 ps range, in good agreement with the experimentally measured value.