Self-assembled monolayers and multilayers of conjugated thiols, α,ω-dithiols, and thioacetyl-containing adsorbates. Understanding attachments between potential molecular wires and gold surfaces

TLDR: In this article, the formation of self-assembled monolayers (SAMs) and multilayers on gold surfaces of rigid-rod conjugated oligomers that have thiol, cr,a.r-dithiol, thioacetyl, or cqor{'ithio-acetyl end groups' was analyzed usingillipsometry, X-ray photoelectron spectroscopy Q(PS), and infrared extemal reflectance spec6oscopy.

Abstract: This paper describes tudies of the formation of self-assembled monolayers (SAMs) and multilayers on gold surfaces of rigid-rod conjugated oligomers that have thiol, cr,a.r-dithiol, thioacetyl, or cqor{'ithioacetyl end groups' The SAMs were analyzed usingillipsom-etry, X-ray photoelectron spectroscopy Q(PS), and infrared extemal reflectance spec6oscopy. The thiol moieties usually dominate adsorption on the gold sites; interactions with the conjugated z-systems are weaker. Rigid rod cr,al-dithiols form *r"*bli"r in which one thiol gouP binds to the surface while the second thiol moiety projects upward at the exposed surface of the SAlvl. ln sinr deprotection of the thiol moieties by deacylation of thioacetyl groups using NFlaOFtpermits formation of SAMs without having to isolate the oxidatively unstable free thiols. Moreover, directidsorption, without exogenous base, of the thioacetyl-terminated oligomers can be accomplished to generate gold surface-bound thiolates. However, in the non-base-promoted adsorptions, higher concentrations of the thioaietyl groups, relative to that of thiol groups, are required to achieve monolayer coverage in a given interval. A thiol-teinninated phenylene-ethynylene system was shown to have a tilt angle of the long molecular axis of <20o from the normal to the substrate surface. These aromatic o-ro-dithiol-derived monolayers provide the basis for studies leading to the design of molecular wires capable of bridging proximate