Columnar self-assembly of a 3D-persulfurated coronene asterisk. The dominant role of Aryl-Sulfur bonds

The synthesis, adsorption behavior, surface structure, and the charge transport properties of a persulfurated coronene asterisk with a 3D-polyaromatic system, namely dodecakis(phenylthio) coronene (DPTC), deposited on HOPG(0001) and Au(111) surfaces, are investigated by means of scanning tunneling microscopy (STM) and spectroscopy (STS). DPTC molecules adsorbed on HOPG(0001) show an orbital mediated tunneling through mainly undisturbed frontier molecular states. DPTC molecules self-assemble on Au(111) into a highly ordered p-stacked columnar "edge-on pattern. The columnar stacking is a gold surface mediated process, as ascertained by fluorescence correlation spectroscopy (FCS). DPTC was monomeric in the precursor solution before assembly. The tunneling spectra of ordered DPTC stacks on Au(111) show an energetic splitting of the frontier molecular states, indicating orbital overlap and supramolecular pi pi interactions of adjacent molecules. DPTCs are sufficiently flexible to facilitate dense 1D stacks. The multiple aryl-sulfur bonds play a dominant role in the modulation of the self-assembly properties of the coronenes which in turn affect their electronic properties. Our results encourage further applications in dendrimer chemistry toward molecular electronics, by using the functionalized coronene core and its multidirectional 3D properties

Arylthio-substituted coronenes as tailored building blocks for molecular electronics

The electron transport through molecules in molecular devices is typically influenced by the nature of the interfaces with the contacting electrodes and by the interactions between neighbouring molecules. It is a major goal of molecular electronics to adjust the electronic function of a molecular device by tailoring the intrinsic molecular properties and the interfacial and intermolecular interactions. Here, we report on the tunability of the electronic properties of coronene derivatives, namely dodecakis(arylthio)coronenes (DATCs), which are found to exhibit a three-dimensional aromatic system. Scanning tunnelling microscopy (STM), spectroscopy (STS) and simulations based on the density functional theory (DFT) are employed to characterize the structural and electronic properties of these molecules deposited on Au(111) surfaces. It is shown that modifications of the peripheral aryl-groups allow us to specifically affect the self-assembly and the charge transport characteristics of the molecules. Molecular assemblies like supramolecular wires with highly delocalized orbitals and single molecules with molecular "quantum dot" characteristics are obtained in this way