Add a third hook: S-acetyl protected oligophenylene pyridine dithiols as advanced precursors for self-assembled monolayers

Self-assembled monolayers (SAMs) of thiols on gold substrates are potentially important systems for future technologies such as molecular electronics and sensing. Especially in molecular electronics a strong interaction and coupling between the “device” molecules and substrate is crucial. In this context, we present here two series of novel SAM precursors, viz. bidentate oligophenylenes with either 1,3-phenylenedimethanethiol or pyridine-2,6-diyldimethanethiol anchoring group. Both series are shown to form densely packed monolayers with a low level of contamination and a high orientational order that are additionally promoted by the interaction between the terminal pyridine moiety and the substrate in the second series. At the same time, most of the SAM constituents do not exhibit a strictly bidentate bonding to the substrate – whereas one anchor group has a thiolate-type bonding, the other is weakly coordinated, unbound, or participating in a disulfide bridge with the adjacent molecules. We believe that such a bonding heterogeneity stems from the fundamental problems of molecular self-assembly in the given case.