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Topological band theory predicts that a topological electronic phase transition between two insulators must proceed via closure of the electronic gap. Here, we use this transition to circumvent the instability of metallic phases in π-conjugated one-dimensional (1D) polymers. By means of density functional theory, tight-binding and GW calculations, we predict polymers near the topological transition from a trivial to a non-trivial quantum phase. We then use on-surface synthesis with custom-designed precursors to make polymers consisting of 1D linearly bridged acene moieties, which feature narrow bandgaps and in-gap zero-energy edge states when in the topologically non-trivial phase close to the topological transition point. We also reveal the fundamental connection between topological classes and resonant forms of 1D π-conjugated polymers.Polymers commonly are semiconducting or insulating because of a sizable energy gap in the density of states around the Fermi level. Yet, the phase transition from topologically trivial to non-trivial in on-surface synthesized π-conjugated polymers, due to a change of resonant form, stabilizes narrow bandgaps and bears in-gap zero-energy edge states in the non-trivial phase.

The development of synthetic strategies to engineer π-conjugated polymers is of paramount importance in modern chemistry and materials science. Here we introduce a synthetic protocol based on the search for specific vibrational modes through an appropriate tailoring of the π-conjugation of the precursors, in order to increase the attempt frequency of a chemical reaction. First, we design a 1D π-conjugated polymer on Au(111), which is based on bisanthene monomers linked by cumulene bridges that tune specific vibrational modes. In a second step, upon further annealing, such vibrational modes steer the twofold cyclization reaction between adjacent bisanthene moieties, which gives rise to a long pentalene-bridged conjugated ladder polymer featuring a low bandgap. In addition, high resolution atomic force microscopy allows us to identify by atomistic insights the resonance form of the polymer, thus confirming the validity of the Glidewell and Lloyd´s rules for aromaticity. This on-surface synthetic strategy may stimulate exploiting previously precluded reactions towards π-conjugated polymers with specific structures and properties. Development of strategies for the synthesis of pi-conjugated polymers is hampered by limited solubility. Here, the authors report a synthetic protocol based on the search for specific vibrational modes through an appropriate tailoring of the p-conjugation of the precursors, in order to increase the attempt frequency of a chemical reaction.

The use of multivalent carbohydrate compounds to block cell-surface lectin receptors is a promising strategy to inhibit the entry of pathogens into cells and could lead to the discovery of novel antiviral agents. One of the main problems with this approach, however, is that it is difficult to make compounds of an adequate size and multivalency to mimic natural systems such as viruses. Hexakis adducts of [60]fullerene are useful building blocks in this regard because they maintain a globular shape at the same time as allowing control over the size and multivalency. Here we report water-soluble tridecafullerenes decorated with 120 peripheral carbohydrate subunits, so-called ‘superballs’, that can be synthesized efficiently from hexakis adducts of [60]fullerene in one step by using copper-catalysed azide–alkyne cycloaddition click chemistry. Infection assays show that these superballs are potent inhibitors of cell infection by an artificial Ebola virus with half-maximum inhibitory concentrations in the subnanomolar range. Tridecafullerenes with 120 peripheral carbohydrate groups have been made in one step from hexakis-adducts of [60]fullerene by using azide–alkyne click chemistry. This synthetic approach offers control over the size and multivalency of these ‘sugar superballs', which are shown to be potent inhibitors of cell infection by an artificial Ebola virus, with IC 50 values in the sub-nanomolar range.

Collective magnetic properties are usually associated with the d or f electrons that carry the individual magnetic moments. A fully spin-polarized ground state based on π electrons has been predicted in half-filled flat-band organic materials, but has remained experimentally challenging to realize. Here we show that isolated tetracyano- p -quinodimethane molecules deposited on graphene epitaxially grown on Ru(0001) acquire charge from the substrate and develop a magnetic moment of 0.4 μ B per molecule. The magnetic moment survives even when the molecules form into a dimer or a monolayer, with a value of 0.18 μ B per molecule for the monolayer. The self-assembled molecular monolayer develops spatially extended spin-split electronic bands, and we visualized the ground-state spin alignment using spin-polarized scanning tunnelling microscopy. The observation of long-range magnetic order in an organic layer adsorbed on graphene paves the way for incorporating magnetic functionalities into graphene. Despite its impressive mechanical and electronic properties, graphene’s magnetic characteristics are poor. However, adsorbed organic molecules can give the material magnetic functionality, and the magnetic moment remains when the molecules combine to form dimers or even a continuous monolayer.

The synthesis of new biocompatible antiviral materials to fight against the development of multidrug resistance is being widely explored. Due to their unique globular structure and excellent properties, [60]fullerene-based antivirals are very promising bioconjugates. In this work, fullerene derivatives with different topologies and number of glycofullerene units were synthesized by using a SPAAC copper free strategy. This procedure allowed the synthesis of compounds 1–3, containing from 20 to 40 mannose units, in a very efficient manner and in short reaction times under MW irradiation. The glycoderivatives were studied in an infection assay by a pseudotyped viral particle with Ebola virus GP1. The results obtained show that these glycofullerene oligomers are efficient inhibitors of EBOV infection with IC50s in the nanomolar range. In particular, compound 3, with four glycofullerene moieties, presents an outstanding relative inhibitory potency (RIP). We propose that this high RIP value stems from the appropriate topological features that efficiently interact with DC-SIGN.

Organic/metal interfaces control the performance of many optoelectronic organic devices, including organic light-emitting diodes or field-effect transistors. Using scanning tunnelling microscopy, low-energy electron diffraction, X-ray photoemission spectroscopy, near-edge X-ray absorption fine structure spectroscopy and density functional theory calculations, we show that electron transfer at the interface between a metal surface and the organic electron acceptor tetracyano- p -quinodimethane leads to substantial structural rearrangements on both the organic and metallic sides of the interface. These structural modifications mediate new intermolecular interactions through the creation of stress fields that could not have been predicted on the basis of gas-phase neutral tetracyano- p -quinodimethane conformation. Interfaces between organic molecules and metal surfaces have a key role in determining the performance of many emerging technologies. Now an intensive experimental study — supported by calculations — of tetracyano- p -quinodimethane molecules on a copper surface, reveals structural rearrangement of both the organic molecules and the surface atoms after charge transfer across the interface.

Fullerene chirality is an important but undeveloped issue of paramount interest in fields such as materials science and medicinal chemistry. So far, enantiopure fullerene derivatives have been made from chiral starting materials or obtained by separating racemic mixtures. Here, we report the enantioselective catalytic synthesis of chiral pyrrolidinofullerenes (the most widely studied fullerene derivatives), which proceeds in high yields under very mild conditions at low temperatures. The combination of a particular metal catalyst—Ag( I ) or Cu( II )—and a chiral ligand is able to direct the cycloaddition of buckminsterfullerene C 60 , the first non-coordinating dipolarophile used in such reactions, to opposite enantiofaces of N -metallated azomethine ylides. This methodology has proven to be quite general, affording enantiomeric excesses of greater than 90%. Furthermore, well-defined chiral carbon atoms linked to the fullerene sphere are able to perturb the inherent symmetry of the fullerene π -system as revealed by circular dichroism measurements. The cycloaddition of N -metalated azomethine ylides to C 60 can result in the formation of a number of different stereoisomeric products. Now, it has been shown that the stereochemical outcome of this reaction can be controlled by carefully choosing the the correct combination of metal and ligand to form the complex that catalyses this process.

The exposure of molecules to attosecond extreme-ultraviolet (XUV) pulses offers a unique opportunity to study the early stages of coupled electron–nuclear dynamics in which the role played by the different degrees of freedom is beyond standard chemical intuition. We investigate, both experimentally and theoretically, the first steps of charge-transfer processes initiated by prompt ionization in prototype donor– π –acceptor molecules, namely nitroanilines. Time-resolved measurement of this process is performed by combining attosecond XUV-pump/few-femtosecond infrared-probe spectroscopy with advanced many-body quantum chemistry calculations. We show that a concerted nuclear and electronic motion drives electron transfer from the donor group on a sub-10-fs timescale. This is followed by a sub-30-fs relaxation process due to the probing of the continuously spreading nuclear wave packet in the excited electronic states of the molecular cation. These findings shed light on the role played by electron–nuclear coupling in donor– π –acceptor systems in response to photoionization. The first steps of charge transfer in molecules after their interaction with light occur on an ultrafast timescale. Now, by combining attosecond pump/few-femtosecond probe spectroscopy with quantum chemistry calculations, it has been shown that a concerted nuclear and electronic motion drives electron transfer in donor– π –acceptor molecules on a sub-10-fs timescale.

We report the synthesis and characterization of a fullerene‐steroid hybrid that contains H2@C60 and a dehydroepiandrosterone moiety synthesized by a cyclopropanation reaction with 76 % yield. Theoretical calculations at the DFT‐D3(BJ)/PBE 6‐311G(d,p) level predict the most stable conformation and that the saturation of a double bond is the main factor causing the upfield shielding of the signal appearing at −3.13 ppm, which corresponds to the H2 located inside the fullerene cage. Relevant stereoelectronic parameters were also investigated and reinforce the idea that electronic interactions must be considered to develop studies on chemical‐biological interactions. A molecular docking simulation predicted that the binding energy values for the protease‐hybrid complexes were −9.9 kcal/mol and −13.5 kcal/mol for PLpro and 3CLpro respectively, indicating the potential use of the synthesized steroid‐H2@C60 as anti‐SARS‐Cov‐2 agent. A H2@C60‐androsterone hybrid has been obtained through a cyclopropanation reaction. The structure was unequivocally determined by a combination of spectroscopic and analytical methods, including extensive NMR experiments. Theoretical calculations at the DFT‐D3(BJ)/PBE 6‐311G(d,p) level allowed the most stable conformation to be determined, and docking simulations suggest activity against SARS‐Cov‐2 proteases.Suarez @nazariolab et al. @unicomplutense @UdeLaHabana report on the synthesis and properties of an androsterone‐H2/C60 hybrid and molecular docking simulations with SARS‐Cov‐2

Amazing aromaticity: ChemPlusChem is pleased to present its special issue on novel aromatic compounds, guest‐edited by Nazario Martín and Yoshito Tobe. This project was initiated following the 2015 ISNA‐16 meeting held in Madrid and the issue features top‐quality contributions covering synthesis, properties and applications of acenes, annulenes, azulenes, fullerenes, oligo(thiophene)s, and porphyrin/phthalocyanines.