Effect of Headgroup on Electrical Conductivity of Self-Assembled Monolayers on Mercury: n-Alkanethiols versus n-Alkaneselenols

Abstract

The relative efficiencies of electron tunneling across self-assembled monolayers (SAMs) of n-alkanethiols and n-alkaneselenols, CH(3)-(CH(2))(n)-XH, where n = 8, 9, 11, and X = S or Se, deposited on mercury electrodes were measured via electroreduction of Ru(NH(3))(6)(3+) in aqueous solutions. Electron tunneling rates across the monolayer films decay exponentially with the monolayer thickness with a tunneling coefficient, beta = 1.1 +/- 0.1 per CH(2) irrespective of the identity of the -XH headgroup. Electron tunneling rates across n-alkanethiol monolayers are ca. 4-fold larger than the rates measured across n-alkaneselenol monolayers containing the same number of carbon atoms, signifying the importance of headgroup/metal contact resistance in electron transfer through SAMs on mercury.

Electrical characterization of single molecule and Langmuir–Blodgett monomolecular films of a pyridine-terminated oligo(phenylene-ethynylene) derivative

“…Particularly prominent examples of metal–molecule contacting groups include thiols [46–47], selenols [48–49], dithiocarbamates [50–51], carbodithioates [52], amines [53–54], esters [55], cyano [56–57], isocyanides [58], nitriles [59], carboxylic acids [24,55,60], dithiocarboxylic acids [52], isothiocyanates [61], dimethylphosphine [62], 4-(methylthio)phenyl groups [63], dihydrobenzo[ b ]thiophenes [64], thienyl rings [65], diphenylphosphine group [66], trimethylsilylethynyl groups [67–69] and fullerenes [60,70–71]. However, many of these groups have significant limitations including chemical degradation at working temperatures [72–73], associated polymerization phenomena [74], small binding energies [74], unexpectedly high contact resistance [75–80], and multiple conductance values due to the variability in the binding geometries [81–86].…”

Mercury Segregation and Diselenide Self-Assembly on Gold

“…28À32 Recent studies suggest that contact resistance of the anchor group is of crucial importance for the electronic transport in molecular junctions. 30,31 The preparation procedures to obtain high quality SAMs (single, compact and ordered phase) for simple molecules such as thiols are basically well-established for surfaces such as gold and silver. 10À32 It is interesting to note that SAMs of alkanethiols on the surface of liquid mercury possess a significantly different structure as compared to that on a gold surfaces.…”

Bottom‐Up Molecular Tunneling Junctions Formed by Self‐Assembly

“…[82][83][84] Although not probed in a Au-SAM/Hg junction, Adaligil et al measured values of b across SAMs of alkanethiolates and selenates using redox couples with SAMcoated working electrodes and found that, in fact, the rate of tunneling was about four times higher across S-Au than it was across Se-Au. [85] Von Wrochem et al formed SAMs by exposing diamines to CS 2 in the presence of an Au substrate. [86] The resulting SAMs are anchored by dithiocarbamates, which form in situ, creating an anchoring group comprising two thiol atoms.…”