Functional Group Effects on the Electrochemical Properties of Carboranethiol Monolayers on Au(111) As Studied by Density Functional Theory: Implications for Organic Electronics

Positional isomers of dicarba-doso-dodecaboranethiols with various functional groups (-NO2, -CHO, -CONH2, -F, -Cl, and -OH) were considered on Au(111) forming (3 x 3) and (5 x 5) structures. Dispersion corrected density functional theory calculations reveal the influence of functional groups on the adsorption characteristics of these carboranethiols depending on the coverage. Functionalized molecules not only possess fascinating chemical and electronic properties but also show stronger chemisorption profiles on gold in relation to the pristine precursors. Molecular dipole moments which can be modified by functional groups were found to be effective in tunability of the work function of deposited surfaces. Results indicate that densely packed adsorption geometries in which functional groups lean toward back of adjacent molecules allowing H-bonding are energetically favorable and enhance stability and ordering of constituents in self-assembled monolayers. Carboranethiols with functional groups are promising to enrich the surface electrochemical properties of resulting surfaces.