Search

It is shown that the self‐assembly of a surface‐confined metal–organic network such as cobalt porphyrins on graphene is accompanied by the evolution of coordination‐dependent observables in the electronic structure: variation of the layer's valence states within almost 1 eV range and of the metal atoms oxidation states. Coordination of cobalt porphyrins, driven by Co ad‐atoms, allows the synthesis of single metal atom centers with +3, +2, or +1 oxidation states. The electronic structure is determined by lateral interactions extending up to a few nanometers, beyond nearest‐neighbor distances. The reactivity of the single Co sites, which is strongly dependent on the local electronic configuration and, thus, on the metal‐specific oxidation state, is probed by carbon monoxide, which is found to ligate at pyridinic Co(I) at room temperature for background pressures above a fraction of a mbar. [ABSTRACT FROM AUTHOR]

We present a protocol for the on‐surface synthesis of polyboroxine molecules derived from boroxine molecules precursors. This process is promoted by oxygen species present on the Au(111) surface: oxygen atoms facilitate the detachment of naphthalene units of trinaphthyl‐boroxine molecules and bridge two unsaturated boroxine centers to form a boroxine‐O‐boroxine chemical motif. X‐ray spectroscopic characterization shows that, as the synthesis process proceeds, it progressively tunes the electronic properties of the interface, thus providing a promising route to control the electron level alignment. [ABSTRACT FROM AUTHOR]

Self‐metalation is a promising route to include a single metal atom in a tetrapyrrolic macrocycle in organic frameworks supported by metal surfaces. The molecule–surface interaction may provide the charge transfer and the geometric distortion of the molecular plane necessary for metal inclusion. However, at a metal surface the presence of an activation barrier can represent an obstacle that cannot be compensated by a higher substrate temperature without affecting the layer integrity. The formation of the intermediate state can be facilitated in some cases by oxygen pre‐adsorption at the supporting metal surface, like in the case of 2H‐TPP/Pd(100). In such cases, the activation barrier can be overcome by mild annealing, yielding the formation of desorbing products and of the metalated tetrapyrrole. We show here that the self‐metalation of 2H‐TPP at the Pd(100) surface can be promoted already at room temperature by the presence of an oxygen gas phase at close‐to‐ambient conditions via an Eley–Rideal mechanism. [ABSTRACT FROM AUTHOR]

Advanced molecular electronic components remain vital for the next generation of miniaturized integrated circuits. Thus, much research effort has been devoted to the discovery of lossless molecular wires, for which the charge transport rate or conductivity is not attenuated with length in the tunneling regime. Herein, we report the synthesis and electrochemical interrogation of DNA-like molecular wires. We determine that the rate of electron transfer through these constructs is independent of their length and propose a plausible mechanism to explain our findings. The reported approach holds relevance for the development of high-performance molecular electronic components and the fundamental study of charge transport phenomena in organic semiconductors. [ABSTRACT FROM AUTHOR]

While the demonstrated power conversion efficiency of organic photovoltaics (OPVs) now exceeds 10%, new design rules are required to tailor interfaces at the molecular level for optimal exciton dissociation and charge transport in higher efficiency devices. We show that molecular shape-complementarity between donors and acceptors can drive performance in OPV devices. Using core hole clock (CHC) X-ray spectroscopy and density functional theory (DFT), we compare the electronic coupling, assembly, and charge transfer rates at the interface between C60 acceptors and flat- or contorted-hexabenzocorone (HBC) donors. The HBC donors have similar optoelectronic properties but differ in molecular contortion and shape matching to the fullerene acceptors. We show that shape-complementarity drives self-assembly of an intermixed morphology with a donor/acceptor (D/A) ball-and-socket interface, which enables faster electron transfer from HBC to C60. The supramolecular assembly and faster electron transfer rates in the shape complementary heterojunction lead to a larger active volume and enhanced exciton dissociation rate. This work provides fundamental mechanistic insights on the improved efficiency of organic photovoltaic devices that incorporate these concave/convex D/A materials. [ABSTRACT FROM AUTHOR]