Self-assembled monolayers have evolved into one of the best established self-assembly systems with high relevance in a scientific and applied context. So far, however, virtually exclusively thiol functional groups have been used for the investigation of fundamental processes on metal surfaces. In this paper, an alternative binding group, the dithiocarbamate (DTC) group, is re-visited. Complete SAM formation with new layer properties characteristically different from thiol SAMs is demonstrated for mono-functional acyclic and bifunctional cyclic dithiocarbamates on Au111 by X-ray photoelectron spectroscopy, cyclic voltammetry, and scanning tunneling microscopy. Furthermore, the chemical adsorption and voltammetric desorption reactions are quantitatively determined. The resonant bi-dentate structure of the DTC provides a characteristically different molecule-metal coupling compared to the thiols and makes the DTC an interesting system for molecular electronics.

We report the observation of supramolecular structures in a self-assembled monolayer (SAM) of diethyldithiocarbamate (DEDTC) on the Au(111) substrate. While all sulfur atoms are found to be covalently anchored to the gold substrate for both DEDTC and DT (decanethiol) monolayers, the self-assembly behavior of DEDTC has been observed to be distinctively different from that of DT. We have found hexagonally arranged trimeric domains of DEDTC molecules in two 30° rotated domains, which we assign to a pattern of chiral trimeric domains. The trimers belong to the C 3 point group, and the supramolecular assembly shows a (2√3 × 2√3)R15° surface structure.

The structure and electrical properties of self-assembled monolayers of cyclic aromatic and aliphatic dithioacetamides (1,4-bis(mercaptoacetamido)benzene and 1,4-bis(mercaptoacetamido)cyclohexane) and of mixed dithioacetamide/alkanethiol monolayers are characterized by X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM) and contact angle goniometry. Both dithioacetamides are found to pack densely on Au(111), however the monolayers are poorly ordered as a result of hydrogen bond formation between the amide groups. The coassembly and the insertion method are compared for the formation of mixed dithioacetamide/alkanethiol monolayers. By coassembly, islands of dithioacetamides in a dodecanethiol matrix can only be obtained at a low dithioacetamide/dodecanethiol concentration ratio in solution (1/10) and by thermal annealing of the resulting monolayers. Small and well defined dithioacetamide domains are realized by insertion of dithioacetamides into defect sites of closely packed octanethiol monolayers. These domains are used to determine the molecular conductance by means of STM height profiles and molecular lengths resulting from density functional theory (DFT) calculations. The difference in the tunneling decay constant beta measured for aromatic dithioacetamides (beta = 0.74-0.76/A) and for aliphatic dithioacetamides (beta = 0.84-0.91/A) highlights the influence of the conjugation within the cyclic core on molecular conductance.

Gradient engineering in SAM: A new method for the fabrication of self‐assembled monolayers (SAMs) based on multi‐component molecular gradients comprising constituents with specific head or tail groups attached to different molecular backbones is presented (see picture). We demonstrate for the first time how STM and NEXAFS methods can be combined with DFT to draw conclusions on structure, orientation and local processes in the gradient layers.

The imposing Rolduc Abbey, pictured here, was the venue for a workshop that brought together an international and interdisciplinary audience focused on topics surrounding the fields of molecular electronics and nanomechanics. The meeting provided an arena to discuss a variety of topics that will, without doubt, play an important role in scientific and technological innovation for the foreseeable future.