This paper describes a molecular diode with high, statistically robust, rectification ratios R of 1.1 × 10(3). These diodes operate with a new mechanism of charge transport based on sequential tunneling involving both the HOMO and HOMO-1 positioned asymmetrically inside the junction. In addition, the diodes are stable and withstand voltage cycling for 1500 times, and the yield in working junctions is 90%.

Following an improved protocol, several monosubstituted 1,1′-biferrocenylenes (BFDs) were prepared as a mixture of α and β constitutional isomers. The isomers were separated and their structures assigned from 1H–1H-COSY and 1H–1H-ROESY NMR data, resulting in a correction of earlier erroneous assignments. Both redox stages (BFD0/BFD+ and BFD+/BFD2+) were examined by cyclic voltammetry. The reactivity of the parent BFD+ versus that of ferrocenium (Fc+) in aqueous solution was evaluated by UV–vis spectroscopy, suggesting that ferrocene should be replaced by BFD derivatives for redox applications in aqueous media due to their more than 1000-fold higher kinetic stability. Electronic transitions of monoalkylated BFD+ derivatives were measured by thin-layer spectroelectrochemistry, revealing unperturbed mixed-valence class III systems independent of α or β substitution.

Even though the surface-assisted dehalogenative coupling constitutes the most abundant protocol in on-surface synthesis, its full potential will only become visible if selectivity issues with polybrominated precursors are comprehensively understood, opening new venues for both organometallic self-assembly and on-surface polymerization. Using the 3,3',5,5'-tetrabromo-2,2',4,4',6,6'-hexafluorobiphenyl (Br4F6BP) at Ag(111), we demonstrate a remote site-selective functionalization at room temperature and a marked temperature difference in double- vs. quadruple activation, both phenomena caused by conformational mechanical effects of the precursor-surface ensemble. The submolecularly resolved structural characterization was achieved by Scanning Tunneling Microscopy, the chemical state was quantitatively assessed by X-ray Photoelectron Spectroscopy, and the analysis of the experimental signatures was supported through first-principles Density-Functional Theory calculations. The non-planarity of the various structures at the surface was specifically probed by additional Near Edge X-ray Absorption Fine Structure experiments. Upon progressive heating, Br4F6BP on Ag(111) shows the following unprecedented phenomena: (1) formation of regular organometallic 1D chains via remote site-selective 3,5'-didebromination; (2) a marked temperature difference in double- vs. quadruple activation; (3) an organometallic self-assembly based on reversibility of C-Ag-C linkages with a thus far unknown polymorphism affording both hexagonal and rectangular 2D networks; (4) extraordinary thermal stability of the organometallic networks. Controlled covalent coupling at the previously Br-functionalized sites was not achieved for the Br4F6BP precursor, in contrast to the comparatively studied non-fluorinated analogue.