Oleksandr

New twist: The first hexapole [9]helicene with an extremely twisted structure has been synthesized and characterized. Formation of each embedded [9]helicene (see scheme, cyan) involves forging of a new C−C bond (purple) to stitch together two [4]helicene subunits, reminiscent of the initial approach Martin developed in the 1960s to make the pristine [9]helicene.

Abstract

Herein we present the first hexapole [9]helicene (H9H). Co‐catalyzed [2+2+2] cyclotrimerization of a dinaphthopyrene (DNP) functionalized alkyne provides the hexaaryl benzene precursor 2, which is transformed into H9H via a dehydrocyclization reaction. Formation of each embedded [9]helicene involves forging of a new C−C bond, which stitches together two [4]helicene subunits of the neighboring DNP blades, reminiscent of the initial method Martin developed for the preparation of [9]helicene in the 1960s. Single‐crystal X‐ray analysis of both 2 and H9H discloses their extremely distorted and crowded structural features. Chiral resolution, optical and electronic properties of H9H are also presented.

The triply linked porphyrin array (porphyrin tape) and recent additions to the triply linked porphyrinoid family including corrole tape, porphyrin‐hexaphyrin hybrid tape, subporphyrin tape, and porphyrin arch‐tape are highlighted in the graphic. These tape‐like molecules can be regarded as polycyclic aromatic molecules, but their optical and electrochemical properties are particularly fascinating, encouraging the study their structure–property relationships. Not only planar molecules, but also distorted structures have been made owing to the development of new synthetic methods. For a full discussion see the Minireview article by T. Tanaka and A. Osuka on https://doi.org/10.1002/chem.201802810page 17188 ff.

Accelerating water dissociation kinetics by isolating cobalt atoms into ruthenium lattice

Accelerating water dissociation kinetics by isolating cobalt atoms into ruthenium lattice, Published online: 23 November 2018; doi:10.1038/s41467-018-07288-6

Magnetic control of a reaction path

Magnetic control of a reaction path, Published online: 21 November 2018; doi:10.1038/s41557-018-0177-6

Enantiopure alleno‐acetylenic cage receptors display a fourfold circular hydrogen‐bonding network of one handedness. Alcohol guests expand the hydrogen‐bonding network of the receptor, forming hydrogen‐bonding topologies reminiscent of those found in isolated water clusters: circular fourfold & docking, pentagonal, linear fivefold, and boat‐shaped hexagonal. The expansion is accompanied by a gain in Gibbs binding energy.

Abstract

Enantiopure (P)₄‐ and (M)₄‐alleno‐acetylenic cage (AAC) receptors form circular fourfold hydrogen‐bonding networks in their closed cage conformation. Theoretical studies reveal a preferential clockwise (cw) orientation of the H‐bonding array for (P)₄‐configured and counterclockwise (ccw) for (M)₄‐configured receptors (ΔE _cw−ccw=−2.6 to −3.1 kcal mol⁻¹). Solution and solid‐state studies show how the H‐bonding network of the receptor is expanded upon encapsulation of alcohol‐containing guests. Topologies reminiscent of those found in isolated water clusters are observed: circular fourfold & docking, pentagonal, linear fivefold, and hexagonal boat‐shaped. Expansion of the H‐bonding network together with optimal space occupancy yields very high ligand affinities (ΔG _293 K=−9.0 kcal mol⁻¹ for endo‐tropine). The H‐bonding network in the complexes also contributes substantially to the enantioselective complexation of chiral diols, such as (R,R)‐ and (S,S)‐trans‐cyclohexane‐1,2‐diol.

Abiotic synthesis of amino acids in the recesses of the oceanic lithosphere

Abiotic synthesis of amino acids in the recesses of the oceanic lithosphere, Published online: 07 November 2018; doi:10.1038/s41586-018-0684-z

Self‐driving: A simple fuel‐driven self‐assembled system is demonstrated that achieves an out‐of‐equilibrium state by dissipating energy from the assembled structures. This occurs by utilizing cooperative effects of the proximally located histidines, which catalyze the hydrolysis of ester bonds of the lipid‐tailed amphiphile.

Abstract

In living systems, dissipative processes are driven by the endergonic hydrolysis of chemical fuels such as nucleoside triphosphates. Now, through a simple model system, a transient self‐assembled state is realized by utilizing the catalytic effect of histidine on the formation and breaking of ester bonds. First, histidine facilitates the ester bond formation, which then rapidly co‐assembles to form a self‐supporting gel. An out‐of‐equilibrium state is realized owing to the cooperative catalysis by the proximal histidines in the assembled state, driving the second pathway and resulting in disassembly to sol. Cooperative effects that use the dual role of imidazoles as nucleophile and as proton donor is utilized to achieve transient assemblies. This simple system mimics the structural journey seen in microtubule formation where the substrate GTP facilitates the non‐covalent assembly and triggers a cooperative catalytic process, leading to substrate hydrolysis and subsequent disassembly.

Self-assembly of polycyclic supramolecules using linear metal-organic ligands

Self-assembly of polycyclic supramolecules using linear metal-organic ligands, Published online: 01 November 2018; doi:10.1038/s41467-018-07045-9

Diffusion-limited reactions in dynamic heterogeneous media

Diffusion-limited reactions in dynamic heterogeneous media, Published online: 23 October 2018; doi:10.1038/s41467-018-06610-6

An issue of some complexity: The activation of single amino acids on mineral surfaces causes polymerization of peptides, but is often limited to disappointingly simple molecules (see figure). Two special systems consisting in couples of amino acids on silica (Glu+Leu and Asp+Val) were observed to give long linear peptides (up to hexamers), with indications of sequence selectivity, raising the interest in such systems for origins of life studies.

Abstract

Evidence for the formation of linear oligopeptides with nonrandom sequences from mixtures of amino acids coadsorbed on silica and submitted to a simple thermal activation is presented. The amino acid couples (glutamic acid+leucine) and (aspartic acid+valine) were deposited on a fumed silica and submitted to a single heating step at moderate temperature. The evolution of the systems was characterized by X‐ray diffraction, infrared spectroscopy, thermosgravimetric analysis, HPLC, and electrospray ionization mass spectrometry (ESI‐MS). Evidence for the formation of amide bonds was found in all systems studied. While the products of single amino acids activation on silica could be considered as evolutionary dead ends, (glutamic acid+leucine) and, at to some extent, (aspartic acid+valine) gave rise to the high yield formation of linear peptides up to the hexamers. Oligopeptides of such length have not been observed before in surface polymerization scenarios (unless the amino acids had been deposited by chemical vapor deposition, which is not realistic in a prebiotic environment). Furthermore, not all possible amino acid sequences were present in the activation products, which is indicative of polymerization selectivity. These results are promising for origins of life studies because they suggest the emergence of nonrandom biopolymers in a simple prebiotic scenario.

Digital coding of mechanical stress in a dynamic covalent shape memory polymer network

Digital coding of mechanical stress in a dynamic covalent shape memory polymer network, Published online: 01 October 2018; doi:10.1038/s41467-018-06420-w

Chemical synthesis generally requires labor-intensive, sometimes tedious trial-and-error optimization of reaction conditions. Here, we describe a plug-and-play, continuous-flow chemical synthesis system that mitigates this challenge with an integrated combination of hardware, software, and analytics. The system software controls the user-selected reagents and unit operations (reactors and separators), processes reaction analytics (high-performance liquid chromatography, mass spectrometry, vibrational spectroscopy), and conducts automated optimizations. The capabilities of this system are demonstrated in high-yielding implementations of C-C and C-N cross-coupling, olefination, reductive amination, nucleophilic aromatic substitution (S_NAr), photoredox catalysis, and a multistep sequence. The graphical user interface enables users to initiate optimizations, monitor progress remotely, and analyze results. Subsequent users of an optimized procedure need only download an electronic file, comparable to a smartphone application, to implement the protocol on their own apparatus.

Here we report an anomalous porous molecular crystal built of C–H···N-bonded double-layered roof-floor components and wall components of a segregatively interdigitated architecture. This complicated porous structure consists of only one type of fully aromatic multijoint molecule carrying three identical dipyridylphenyl wedges. Despite its high symmetry, this molecule accomplishes difficult tasks by using two of its three wedges for roof-floor formation and using its other wedge for wall formation. Although a C–H···N bond is extremely labile, the porous crystal maintains its porosity until thermal breakdown of the C–H···N bonds at 202°C occurs, affording a nonporous polymorph. Though this nonporous crystal survives even at 325°C, it can retrieve the parent porosity under acetonitrile vapor. These findings show how one can translate simplicity into ultrahigh complexity.

Network connections: Molecular networks of dynamic multilevel systems can exhibit different connectivities between nodes. In this Concept article, different molecular networks that can be produced by combinations of different reaction types and synthetic systems are discussed.

Abstract

Dynamic multilevel systems can be assembled from molecular building blocks through two or more reversible reactions that form covalent bonds. Molecular networks of dynamic multilevel systems can exhibit different connectivities between nodes. The design and creation of molecular networks in multilevel systems require control of the crossed reactivity of the functional groups (how to connect nodes) and the conditions of the reactions (when to connect nodes). In recent years, the combination of orthogonal and communicating reactions, which can be simultaneous or individually activated, has produced a variety of systems that have given rise to macrocycles and cages, as well as molecular motors and multicomponent architectures on surfaces. A given set of reactions can lead to systems with unique responsiveness, compositions, and functions as a result of the relative reactivities. In this Concept article, different molecular networks from synthetic systems that can be produced by combinations of different reaction types are discussed. Moreover, applications of this chemistry are highlighted, and future perspectives are envisioned.

Supramolecular nanoassemblies that respond to multiple stimuli exhibit high therapeutic efficacy against malignant tumors. We report a new type of supramolecular nanofiber that integrates targeting peptide–coated magnetic nanoparticles with β-cyclodextrin–bearing polysaccharides in a complex held together by multivalent interactions. The nanofibers not only exhibited reversible photo-triggered association and disassociation depending on irradiation wavelength but also underwent magnetic field–controlled directional aggregation, even in the rather weak geomagnetic field. The nanofibers markedly suppressed invasion by and metastasis of cancer cells both in vitro and in vivo. Furthermore, compared with control mice, tumor-burdened mice treated with the nanofibers showed a lower rate of mortality from the metastatic spread of tumor cells. Our results suggest that these geomagnetism- and photo-controlled nanofibers may facilitate the rapid development of efficacious anticancer therapies.

Concyclic CH-π arrays for single-axis rotations of a bowl in a tube

Concyclic CH-π arrays for single-axis rotations of a bowl in a tube, Published online: 17 September 2018; doi:10.1038/s41467-018-06270-6