The Scope of Direct Alkylation of Gold Surface with Solutions of C₁–C₄ n-Alkylstannanes

Abstract

Treatment of cleaned gold surfaces with dilute tetrahydrofuran or chloroform solutions of tetraalkylstannanes (alkyl = methyl, ethyl, n-propyl, n-butyl) or di-n-butylmethylstannyl tosylate under ambient conditions causes a self-limited growth of disordered monolayers consisting of alkyls and tin oxide. Extensive use of deuterium labeling showed that the alkyls originate from the stannane and not from ambient impurities, and that trialkylstannyl groups are absent in the monolayers, contrary to previous proposals. Methyl groups attached to the Sn atom are not transferred to the surface. Ethyl groups are transferred slowly, and propyl and butyl rapidly. In all cases, tin oxide is codeposited in submonolayer amounts. The monolayers were characterized by ellipsometry, contact angle goniometry, polarization modulated IR reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy with ferrocyanide/ferricyanide, which revealed a very low charge-transfer resistance. The thermal stability of the monolayers and their resistance to solvents are comparable with those of an n-octadecanethiol monolayer. A preliminary examination of the kinetics of monolayer deposition from a THF solution of tetra-n-butylstannane revealed an approximately half-order dependence on the bulk solution concentration of the stannane, hinting that more than one alkyl can be transferred from a single stannane molecule. A detailed structure of the attachment of the alkyl groups is not known, and it is proposed that it involves direct single or multiple bonding of one or more C atoms to one or more Au atoms.

Stable Carboxylate‐Terminated Gold Surfaces Produced by Spontaneous Grafting of an Alkyltin Compound

“…In our case, the presence of Sn (Figure 3d and Figure SI-4c in the Supporting Information;X PS signals of Sn 3d 5/2 at 487.3 eV and Sn 3d 3/2 at 496.2 eV)s uggested the formationo f coordination compounds with the oxygen atoms of the free carboxylic moieties by releasing the chlorine groups, which produced negligible XPS signals (Figure 3e and FigureSI-4 di n the SupportingI nformation). This promotes the formation of thicker layers (Figure 4) than those reported for neutral compounds, [22][23][24] and that reported for am onolayer of mercaptopropionic acid. [28] An estimation of the thickness of the organic layer was carried out by calculating the average layer thickness based on the attenuation of the XPS Au 4f 7/2 peak following surface modification.…”

Precise Control of Interfacial Charge Transport for Building Functional Optoelectronic Devices

“…We list below three general methods for in situ generation of AuC covalent contacts. The first method adopts the reactivity of CSnR 3 bonds based on transmetalation to generate AuC bonds on gold surfaces . However, this approach uses and produces toxic and volatile trimethyltin species, which limits its wide application.…”

Mechanism of Surface Alkylation of a Gold Aerogel with Tetra-n-butylstannane-d36: Identification of Byproducts

“…More recent experiments with deuterated alkylstannanes showed that under the ambient conditions used this cannot be entirely correct. Although tin is co-deposited with the alkyls, it does not appear as a trialkylstannyl group, whose deuterated form would be detectable in IR spectra, but as a tin oxide, detected by XPS . In the one case in which the alkylation reaction order with respect to stannane concentration in bulk solution was determined, it was found to be 0.5.…”

“…This treatment is known to coat a flat surface of gold, mostly Au(111), with an alkyl-containing monolayer . It is significant for at least two reasons: (i) the resulting layers are distinct from those commonly produced by treatment with alkanethiols in their permeability and thermal and chemical stability, and (ii) direct carbon-to-gold attachment has much higher electrical conductivity than attachment through a sulfur atom. , While methyl groups are not transferred from a tin atom to the Au surface and ethyl groups are transferred only very slowly, propyl and longer alkyl groups are transferred efficiently . Similar solution alkylation processes do not proceed under ambient conditions with alkylsilanes, but they do take place with the organomercurials RHgX. , …”