Oleksandr

A perylene bisimide dye self-assembles via hydrogen-bonding and π–π interactions into J-aggregates, which in turn organize into liquid-crystalline columnar domains. The dye molecules organize with the cores parallel to the columnar axis, forming an unprecedented triple stranded helical structure with transition dipoles μ_ag pointing along the columnar axis.

[Communication]
Stefanie Herbst, Bartolome Soberats, Pawaret Leowanawat, Matthias Lehmann, Frank Würthner
Angew. Chem. Int. Ed., January 16, 2017, DOI: 10.1002/anie.201612047. Read article

Turn on the detector: Upon activation by UV light, diarylethenes carrying an internal aldehyde group undergo a rearrangement reaction in the presence of biogenic amines, which facilitates their colorimetric detection (see scheme).

[Communication]
Virginia Valderrey, Aurelio Bonasera, Sebastian Fredrich, Stefan Hecht
Angew. Chem. Int. Ed., January 16, 2017, DOI: 10.1002/anie.201609989. Read article

Nature Chemistry. doi:10.1038/nchem.2703

Authors: Saidul Islam, Dejan-Krešimir Bučar & Matthew W. Powner

2-aminothiazole — a hybrid of prebiotic amino acid and nucleotide precursors — sequentially accumulates and purifies glycolaldehyde and glyceraldehyde from complex mixtures in the order required for ribonucleotide synthesis, dynamically resolves glyceraldehyde from its ketose-isomer dihydroxyacetone, and provides the first strategy to select natural amino acids from abiotic aldehydes and ketones.

Knots may ultimately prove just as versatile and useful at the nanoscale as at the macroscale. However, the lack of synthetic routes to all but the simplest molecular knots currently prevents systematic investigation of the influence of knotting at the molecular level. We found that it is possible to assemble four building blocks into three braided ligand strands. Octahedral iron(II) ions control the relative positions of the three strands at each crossing point in a circular triple helicate, while structural constraints on the ligands determine the braiding connections. This approach enables two-step assembly of a molecular 819 knot featuring eight nonalternating crossings in a 192-atom closed loop ~20 nanometers in length. The resolved metal-free 819 knot enantiomers have pronounced features in their circular dichroism spectra resulting solely from topological chirality. Authors: Jonathan J. Danon, Anneke Krüger, David A. Leigh, Jean-François Lemonnier, Alexander J. Stephens, Iñigo J. Vitorica-Yrezabal, Steffen L. Woltering

Aromatic and antiaromatic ring currents in a molecular nanoring

Nature 541, 7636 (2017). doi:10.1038/nature20798

Authors: Martin D. Peeks, Timothy D. W. Claridge & Harry L. Anderson

Aromatic and antiaromatic molecules—which have delocalized circuits of [4n + 2] or [4n] electrons, respectively—exhibit ring currents around their perimeters. The direction of the ring current in an aromatic molecule is such as to generate a magnetic field that opposes the external field inside the ring (a ‘diatropic’ current), while the ring current in an antiaromatic molecule flows in the reverse direction (‘paratropic’). Similar persistent currents occur in metal or semiconductor rings, when the phase coherence of the electronic wavefunction is preserved around the ring. Persistent currents in non-molecular rings switch direction as a function of the magnetic flux passing through the ring, so that they can be changed from diatropic (‘aromatic’) to paratropic (‘antiaromatic’) simply by changing the external magnetic field. As in molecular systems, the direction of the persistent current also depends on the number of electrons. The relationship between ring currents in molecular and non-molecular rings is poorly understood, partly because they are studied in different size regimes: the largest aromatic molecules have diameters of about one nanometre, whereas persistent currents are observed in microfabricated rings with diameters of 20–1,000 nanometres. Understanding the connection between aromaticity and quantum-coherence effects in mesoscopic rings provides a motivation for investigating ring currents in molecules of an intermediate size. Here we show, using nuclear magnetic resonance spectroscopy and density functional theory, that a six-porphyrin nanoring template complex, with a diameter of 2.4 nanometres, is antiaromatic in its 4+ oxidation state (80 π electrons) and aromatic in its 6+ oxidation state (78 π electrons). The antiaromatic state has a huge paramagnetic susceptibility, despite having no unpaired electrons. This work demonstrates that a global ring current can be promoted in a macrocycle by adjusting its oxidation state to suppress the local ring currents of its components.The discovery of ring currents around a molecule with a circumference of 7.5 nanometres, at room temperature, shows that quantum coherence can persist in surprisingly large molecular frameworks.

Nature Chemistry. doi:10.1038/nchem.2684

Authors: Tomoya Fukui, Shinnosuke Kawai, Satoko Fujinuma, Yoshitaka Matsushita, Takeshi Yasuda, Tsuneaki Sakurai, Shu Seki, Masayuki Takeuchi & Kazunori Sugiyasu

Unlike in biomolecular systems, synthetic self-assembly is largely spontaneous, thus limiting the complexity and functionality of the materials one can create. Now, self-assembly under out-of-equilibrium conditions is demonstrated for a metastable supramolecular system. Differentiation of nanoparticles into nanofibers and nanosheets — with electronically distinct states — is achieved through kinetic control, illustrating pathway-dependent material properties.

Hydrophobicity plays an important role in numerous physicochemical processes from the process of dissolution in water to protein folding, but its origin at the fundamental level is still unclear. The classical view of hydrophobic hydration is that, in the presence of a hydrophobic solute, water forms transient microscopic “icebergs” arising...

Violins made by Antonio Stradivari are renowned for having been the preferred instruments of many leading violinists for over two centuries. There have been long-standing questions about whether wood used by Stradivari possessed unique properties compared with modern tonewood for violin making. Analyses of maple samples removed from four Stradivari...

Abstract

A bio-inspired synthetic supramolecular system is reported that undergoes changes in its helical conformation transiently as an active material and at the expense of ATP molecules as fuel in an “enzyme-in-tandem” approach.

[Communication]
Shikha Dhiman, Ankit Jain, Subi J. George
Angew. Chem. Int. Ed., December 29, 2016, DOI: 10.1002/anie.201610946. Read article

Self-assembly of tetravalent Goldberg polyhedra from 144 small components

Nature 540, 7634 (2016). doi:10.1038/nature20771

Authors: Daishi Fujita, Yoshihiro Ueda, Sota Sato, Nobuhiro Mizuno, Takashi Kumasaka & Makoto Fujita

Rational control of the self-assembly of large structures is one of the key challenges in chemistry, and is believed to become increasingly difficult and ultimately impossible as the number of components involved increases. So far, it has not been possible to design a self-assembled discrete molecule made up of more than 100 components. Such molecules—for example, spherical virus capsids—are prevalent in nature, which suggests that the difficulty in designing these very large self-assembled molecules is due to a lack of understanding of the underlying design principles. For example, the targeted assembly of a series of large spherical structures containing up to 30 palladium ions coordinated by up to 60 bent organic ligands was achieved by considering their topologies. Here we report the self-assembly of a spherical structure that also contains 30 palladium ions and 60 bent ligands, but belongs to a shape family that has not previously been observed experimentally. The new structure consists of a combination of 8 triangles and 24 squares, and has the symmetry of a tetravalent Goldberg polyhedron. Platonic and Archimedean solids have previously been prepared through self-assembly, as have trivalent Goldberg polyhedra, which occur naturally in the form of virus capsids and fullerenes. But tetravalent Goldberg polyhedra have not previously been reported at the molecular level, although their topologies have been predicted using graph theory. We use graph theory to predict the self-assembly of even larger tetravalent Goldberg polyhedra, which should be more stable, enabling another member of this polyhedron family to be assembled from 144 components: 48 palladium ions and 96 bent ligands.

Abstract

In the focal point: The integration of chalcogen bonds into non-covalent catalytic systems is realized with deep σ holes and wide bite angles between cofacial endocyclic sulfur atoms of dithieno[3,2-b;2′,3′-d]thiophenes (DTTs), ready to activate hydride acceptors for transfer hydrogenation of quinolines and imines by lone-pair recognition in the transition state.

[Communication]
Sebastian Benz, Javier López-Andarias, Jiri Mareda, Naomi Sakai, Stefan Matile
Angew. Chem. Int. Ed., December 16, 2016, DOI: 10.1002/anie.201611019. Read article

We consider an important class of self-assembly problems, and using the formalism of stochastic thermodynamics, we derive a set of design principles for growing controlled assemblies far from equilibrium. The design principles constrain the set of configurations that can be obtained under nonequilibrium conditions. Our central result provides intuition for...

Nature Chemistry. doi:10.1038/nchem.2674

Authors: Yingfeng Tu, Fei Peng, Xiaofeng Sui, Yongjun Men, Paul B. White, Jan C. M. van Hest & Daniela A. Wilson

Effective regulation over the motion of self-propelled micro- and nanomotors is a challenging proposition. Now, self-assembled stomatocyte nanomotors with thermoresponsive polymer brushes have been designed that sense changes in local temperature and regulate the accessibility of the hydrogen peroxide fuel — thereby adjusting the speed and behaviour of nanomotor itself.