On the nucleation and fast reaction kinetics of 2D polymerisation with a 2-in-1 monomer.

We report on the fast reaction kinetics of an imine based 2D polymer (2DP) formed from a single monomer carrying both aldehyde and amine groups. Our results point towards a direct monomer-to-crystalline polymer transition without an amorphous intermediate.

2D self-assembly and electronic characterization of oxygen-boron-oxygen-doped chiral graphene nanoribbons.

Graphene nanoribbons (GNRs), quasi-one-dimensional strips of graphene, exhibit a nonzero bandgap due to quantum confinement and edge effects. In the past decade, different types of GNRs with atomically precise structures have been synthesized by a bottom-up approach and have attracted attention as a novel class of semiconducting materials for applications in electronics and optoelectronics. We report the large-scale, inexpensive growth of high-quality oxygen-boron-oxygen-doped chiral GNRs with a defined structure using chemical vapor deposition.

Crystalline supramolecular organic frameworks via hydrogen-bonding between nucleobases.

We report a crystalline supramolecular framework assembled by H-bonding interactions between covalently fused monomers equipped with two guanine-cytosine nucleobase pairs.

Carbocatalysis with pristine graphite: on-surface nanochemistry assists solution-based catalysis.

Carbocatalysis holds a privileged position as a sustainable alternative to metal-based catalysis. While the focus in solution-based catalytic processes generally lies on how the heterogeneous catalyst affects the solution composition, more attention has recently been given to the analysis of the carbon material itself. Various outstanding surface characterisation techniques, efficient in assessing the catalyst on-surface composition, are now available.

Elucidating Noncovalent Reaction Mechanisms: G-Quartet as an Intermediate in G-Quadruplex Assembly.

In analogy to covalent reactions, the understanding of noncovalent association pathways is fundamental to influence and control any supramolecular process. Following an approach that is reminiscent of covalent methodologies, we study here, for the first time, the mechanism of G-quadruplex formation in organic solvents. Our results support a reaction pathway in which the cation shifts the equilibrium towards a G-quartet transient intermediate, which then acts as a template in the formation of the G-quadruplex product.

Anatomy of On-Surface Synthesized Boroxine Two-Dimensional Polymers.

Synthetic two-dimensional polymers (2DPs) obtained from well-defined monomers bottom-up fabrication strategies are promising materials that can extend the realm of inorganic 2D materials. The on-surface synthesis of such 2DPs is particularly popular, however the pathway complexity in the growth of such films formed on solid surfaces is poorly understood. In this contribution, we present a straightforward experimental protocol which allows the synthesis of large-area, defect-free 2DPs based on boroxine linkages at room temperature.

Epidemiology of acute pediatric poisonings in Spain: a prospective multicenter study from the Spanish Society of Pediatric Emergency Medicine.

Objective: To identify types of childhood poisoning exposures leading to consultation to emergency departments (ED) in Spain.

Methods: We carried out a multicenter prospective registry-based cohort study including children with acute poisonings presenting to 55 pediatric EDs of the Spanish Society of Pediatric Emergency Medicine between 2008 and 2017, during previously designated certain days.

Results: During the study period, we registered 749 803 pediatric ED presentations, of which 1749 were for poisonings (0.

Tunable Superstructures of Dendronized Graphene Nanoribbons in Liquid Phase.

In this Communication, we report the first synthesis of structurally well-defined graphene nanoribbons (GNRs) functionalized with dendritic polymers. The resultant GNRs possess grafting ratios of 0.59-0.

Halogenated building blocks for 2D crystal engineering on solid surfaces: lessons from hydrogen bonding.

Halogen bonding has emerged as a promising tool in two-dimensional (2D) crystal engineering. Since halogen bonds are similar to hydrogen bonds in a number of aspects, the existing knowledge of hydrogen bonded systems can be applied to halogenated systems. Here we evaluate the applicability of a retrosynthetic approach based on topological similarity between hydrogen and halogen bonds to obtain predictable halogen bonded networks.

The impact of grafted surface defects on the on-surface Schiff-base chemistry at the solid-liquid interface.

We investigate the effect of covalently modified graphitic surfaces on the formation of single-layer covalent organic frameworks (sCOFs) at the solid-liquid interface. The impact of different densities of grafted aryl species was tested on the on-surface synthesis of three distinct imine-based 2D sCOFs. The grafted aryl species that act as defects provide steric barriers to the progress of the Schiff-base reaction, and can be locally removed to start the 2D polymer healing process.

Impact of Conformational Effects on the Ring-Chain Equilibrium of Hydrogen-Bonded Dinucleosides.

Supramolecular ring-versus-chain equilibria are ubiquitous in biological and synthetic systems. Understanding the factors that decide whether a system will fall on one side or the other is crucial to the control of molecular self-assembly. This work reports results with two kinds of dinucleoside monomers, in which the balance between closed cycles and open polymers is found to depend on subtle factors that rule conformational equilibria, such as steric hindrance, intramolecular interactions, or π-conjugation pathways.

Lateral Fusion of Chemical Vapor Deposited N = 5 Armchair Graphene Nanoribbons.

Bottom-up synthesis of low-bandgap graphene nanoribbons with various widths is of great importance for their applications in electronic and optoelectronic devices. Here we demonstrate a synthesis of N = 5 armchair graphene nanoribbons (5-AGNRs) and their lateral fusion into wider AGNRs, by a chemical vapor deposition method. The efficient formation of 10- and 15-AGNRs is revealed by a combination of different spectroscopic methods, including Raman and UV-vis-near-infrared spectroscopy as well as by scanning tunneling microscopy.

Hydrogen-Bonded Macrocyclic Supramolecular Systems in Solution and on Surfaces.

Cyclization into closed assemblies is the most recurrent approach to realize the noncovalent synthesis of discrete, well-defined nanostructures. This review article particularly focuses on the noncovalent synthesis of monocyclic hydrogen-bonded systems that are self-assembled from a single molecule with two binding-sites. Taking advantage of intramolecular binding events, which are favored with respect to intermolecular binding in solution, can afford quantitative amounts of a given supramolecular species under thermodynamic control.

Two-Dimensional Nanoporous Networks Formed by Liquid-to-Solid Transfer of Hydrogen-Bonded Macrocycles Built from DNA Bases.

We present an approach that makes use of DNA base pairing to produce hydrogen-bonded macrocycles whose supramolecular structure can be transferred from solution to a solid substrate. A hierarchical assembly process ultimately leads to two-dimensional nanostructured porous networks that are able to host size-complementary guests.

Role of the Symmetry of Multipoint Hydrogen Bonding on Chelate Cooperativity in Supramolecular Macrocyclization Processes.

Herein, we analyze the intrinsic chelate effect that multipoint H-bonding patterns exert on the overall energy of dinucleoside cyclic systems. Our results indicate that the chelate effect is regulated by the symmetry of the H-bonding pattern, and that the effective molarity is reduced by about three orders of magnitude when going from the unsymmetric ADD-DAA or DDA-AAD patterns to the symmetric DAD-ADA pattern.

High-fidelity noncovalent synthesis of hydrogen-bonded macrocyclic assemblies.

A hydrogen-bonded cyclic tetramer is assembled with remarkably high effective molarities from a properly designed dinucleoside monomer. This self-assembled species exhibits an impressive thermodynamic and kinetic stability and is formed with high fidelities within a broad concentration range.