Evidence for Carbon-Sulfur Bond Cleavage in Spontaneously Adsorbed Organosulfide-Based Monolayers at Gold

Abstract

We have recently described several aspects of the electrode reactions of monolayers formed from alkanethiols and dialkyl disulfides at gold. This paper now discusses the findings and implications of two sets of electrochemical and surface characterization studies viz., X-ray photoelectron (XPS) and infrared reflection (IRS) spectroscopies. The first set of studies characterized monolayers formed at mica-supported Au(111) from dilute (0.1-1 mM) ethanolic solutions of butanethiol (BT) and butyl sulfide (BS/Au). The second set of experiments compared the monolayers formed from an asymmetric aryl sulfide, ethyl phenyl sulfide (PES), and a symmetric aryl sulfide, phenyl sulfide (PS), with those from thiophenol (TP) and ethanethiol (ET). The similarities in the E[sub p] and Q[sub d] values at TP/Au and PS/Au are consistent with the observations and subsequent interpretation of the electrochemical data at BT/Au and BS/Au. That is, the sulfur-gold interactions at TP/Au and PS/Au are effectively indistinguishable. Together, the above findings provide clear evidence for S-C cleavage in monolayers prepared at gold from organosulfides. 19 refs., 2 figs.