Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: The extraordinary success of graphene and its tremendous potential applications [1] paved the way for the rising of a completely new family of two dimensional materials. [2] Graphene is a semimetal with zero-gap, which limits its use in the electronics technology. Transition metal dichalcogenides present a band gap in the range of 1.5 -2.5 eV [3] (depending on the thickness, strain level and chemical composition), which makes them inappropriate for some optoelectronics applications where band gaps in the 0.1 -1 eV range are commonly preferred. [4] Black phosphorous (BP), [5] a layered allotrope of phosphorous, presents an energy gap in this range and hence it is now intensely studied to better understand its electronics properties in the few-layer conformation. However, it shows a relatively large reactivity. Exfoliated flakes of BP are highly hygroscopic and tend to uptake moisture from

We present a thorough theoretical study of the adsorption of acrolein (ACO), acrylonitrile (ACN) and acrylamide (ACA) on a Cu(100) surface. To this, we have used the Density Functional Theory (DFT), imposing Periodic Boundary Conditions (PBC) to have a correct description of the electronic band structure of the metal, and including dispersion forces through two different schemes: the D2 method of Grimme and the vdW-DF. We have found several adsorption geometries; In all of them, the vinyl group together with the amide (in ACA), ciano (in ACN) and carbonyl (in ACO) groups, is highly involved. The highest adsorption energy is found for acrylamide, followed by acrolein and the lowest for acrylonitrile (depending on the level of theory employed ∼ 1.2, 1.0, 0.9 eV respectively). We show that a strong coupling between the π electronic system (both occupied and virtual orbitals) and the electronic levels of the metal * To whom correspondence should be addressed † Chemistry-UAM ‡ IFIMAC ¶ IAdChem is the main responsible of the chemisorption. As a consequence, electronic density is transferred from the surface to the molecule, whose carbon atoms acquire a partial sp 3 hybridization. Lone pair orbitals of the cyano, amide and carbonyl groups also play a role in the interaction. The simulations and following analysis allow to disentangle the nature of the interaction, which can be explained on the basis of a simple chemical picture: donation from the occupied lone pair and π orbitals of the molecule to the surface and backdonation from the surface to the π * orbital of the molecule (π−backbonding).

The combination of alkyne and halogen functional groups in the same molecule allows for the possibility of many different reactions when utilized in on-surface synthesis. Here, we use a pyrene-based precursor with both functionalities to examine the preferential reaction pathway when it is heated on an Au(111) surface. Using high-resolution bond-resolving scanning tunneling microscopy, we identify multiple stable intermediates along the prevailing reaction pathway that initiate with a clearly dominant Glaser coupling, together with a multitude of other side products. Importantly, control experiments with reactants lacking the halogen functionalization reveal the Glaser coupling to be absent and instead show the prevalence of non-dehydrogenative head-to-head alkyne coupling. We perform scanning tunneling spectroscopy on a rich variety of the product structures obtained in these experiments, providing key insights into the strong dependence of their HOMO–LUMO gaps on the nature of the intramolecular coupling. A clear trend is found of a decreasing gap that is correlated with the conversion of triple bonds to double bonds via hydrogenation and to higher levels of cyclization, particularly with nonbenzenoid product structures. We rationalize each of the studied cases.

The advent of on-surface chemistry under vacuum has vastly increased our capabilities to synthesize carbon nanomaterials with atomic precision. Among the types of target structures that have been synthesized by these means, graphene nanoribbons (GNRs) have probably attracted the most attention. In this context, the vast majority of GNRs have been synthesized from the same chemical reaction: Ullmann coupling followed by cyclodehydrogenation. Here, we provide a detailed study of the growth process of five-atom-wide armchair GNRs starting from dibromoperylene. Combining scanning probe microscopy with temperature-dependent XPS measurements and theoretical calculations, we show that the GNR growth departs from the conventional reaction scenario. Instead, precursor molecules couple by means of a concerted mechanism whereby two covalent bonds are formed simultaneously, along with a concomitant dehydrogenation. Indeed, this alternative reaction path is responsible for the straight GNR growth in spite of the initial mixture of reactant isomers with irregular metal–organic intermediates that we find. The provided insight will not only help understanding the reaction mechanisms of other reactants but also serve as a guide for the design of other precursor molecules.

On page 6332, J. Gómez-Herrero, F. Zamora, and co-workers describe the isolation of antimonene, a new allotrope of antimony that consists of a single layer of atoms. They obtain antimonene flakes by the scotch tape method; these flakes are highly stable in ambient conditions and even when immersed in water. The 1.2 eV gap calculated in this study suggests potential applications in optoelectronics.