All-cis-hexafluoro- and all-cis-pentafluoro-cyclohexane (PFCH) derivatives are new kinds of materials, the structures and properties of which are dominated by the highly dipolar Janus-face motif. Here, we report on the effects of integrating the PFCH groups into self-assembled monolayers (SAMs) of alkanethiolates on Au(111). Monolayers with an odd (eleven) and even (twelve) number of methylene groups were characterized in detail by several complementary experimental tools, supported by theoretical calculations. Surprisingly, all the data show a high similarity of both kinds of monolayers, nearly lacking the typically observed odd-even effects. These new monolayers have a packing density about 1/3 lower than that of non-substituted alkanethiolate monolayers, caused by the bulkiness of the PFCH moieties. The orientations of the PFCH groups and the alkyl chains could be determined independently, suggesting a conformation similar to the one found in the solid state structure of an analogous compound. Although in the SAMs the PFCH groups are slightly tilted away from the surface normal with the axial fluorine atoms pointing downwards, most of the dipole moments of the group remain oriented parallel to the surface, which is a unique feature for a SAM system. The consequences are much lower water contact angles compared to other partly fluorinated SAMs as well as rather moderate work function values. The interaction between the terminal PFCH moieties results in an enhanced stability of the PFCH-decorated SAMs toward exchange reaction with potential molecular substituents in spite of the lower packing density of these films.

A series of molecules with oligophenylene backbone, thiolate anchoring group, and pentafluoro-λ⁶-sulfanyl (−SF₅) tail group was synthesized and used as precursors to form self-assembled monolayers (SAMs) on Au(111) substrates. The resulting SAMs feature dense molecular packing, upright molecular orientation, and chemically homogeneous SAM-ambient interface, comprised entirely of the −SF₅ moieties. These SAMs exhibit exceptional wetting and electrostatic properties, showing advancing water contact angles up to 103° and work function values up to 5.96 eV—probably the highest values reported for any aromatic monolayers on gold. They also feature a comparably low value of the tunnelling decay coefficient (0.38 ± 0.07 Å⁻¹), typical of oligophenylene backbone, which is not affected by the introduction of the −SF₅ group. The latter also hardly affects the current densities at a specific bias compared to analogous monolayers with other electronegative tail groups. The superior electrostatic and good charge transport properties of the designed, SF₅-terminated SAMs make them potentially useful for interface engineering in organic electronics and photovoltaics.

While self-assembled monolayers (SAMs) of aromatic thiolates are frequently used in a wide range of applications, their formation is often hampered by the low solubilities of their precursors. Here we introduce the 3,4-dimethoxybenzyl group as a protective group for the thiol moiety, which increases the solubility and stability of the precursor, but becomes cleaved off during monolayer formation, especially at elevated temperature (60 °C) and in presence of protons (trifluoroacetic acid). For a series of substituted terphenylthiols as model systems, it could be demonstrated by using ellipsometry, infrared-reflection absorption spectroscopy, and scanning-tunneling microscopy that the resulting SAMs have the same structure and quality as the ones obtained from the respective unprotected thiols. The protective group has the additional advantage to be stable under Pd-catalyzed C–C bond formation reaction conditions, facilitating the syntheses of the respective precursors.