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-closo-dodecaboranethiols
with various
functional groups (−NO2, −CHO, −CONH2, −F, −Cl, and −OH) were considered on
Au(111) forming (3 × 3) and (5 × 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.