Search

The desire to construct complex molecular systems is driven by the need for technological (r)evolution and our intrinsic curiosity to comprehend the origin of life. Supramolecular chemists tackle this challenge by combining covalent and noncovalent reactions leading to multicomponent systems with emerging complexity. However, this synthetic strategy often coincides with difficult preparation protocols and a narrow window of suitable conditions. Here, we report on unsuspected observations of our group that highlight the impact of subtle “irregularities” on supramolecular systems. Based on the effects of pathway complexity, minute amounts of water in organic solvents or small impurities in the supramolecular building block, we discuss potential pitfalls in the study of complex systems. This article is intended to draw attention to often overlooked details and to initiate an open discussion on the importance of reporting experimental details to increase reproducibility in supramolecular chemistry.

Control over molecular motion is facilitated in materials with highly ordered nanoscale structures. Here we report on the fabrication of cholesteric liquid-crystal networks by circularly polarized light irradiation, without the need for chiral dopant or plasticizer. The polymer network is obtained by photopolymerization of a smectic achiral diacrylate mesogen consisting of an azobenzene core and discrete oligodimethylsiloxane tails. The synchronous helical photoalignment and photopolymerization originate from the cooperative movement of the mesogens ordered in well-defined responsive structures, together with the flexibility of the oligodimethylsiloxane blocks. The resulting thin films show excellent thermal stability and light-induced memory features with reversible responses. Additionally, we demonstrate the fabrication of photo-patterned films of liquid-crystal networks with opposite helical senses. These findings provide a new method to make light-controllable chiroptical materials with exciting applications in optics and photonics.

Small‐molecule stabilization of protein–protein interactions (PPIs) is a promising concept in drug discovery, however the question how to identify or design chemical starting points in a “bottom‐up” approach is largely unanswered. We report a novel concept for identifying initial chemical matter for PPI stabilization based on imine‐forming fragments. The imine bond offers a covalent anchor for site‐directed fragment targeting, whereas its transient nature enables efficient analysis of structure–activity relationships. This bond enables fragment identification and optimisation using protein crystallography. We report novel fragments that bind specifically to a lysine at the PPI interface of the p65‐subunit‐derived peptide of NF‐κB with the adapter protein 14‐3‐3. Those fragments that subsequently establish contacts with the p65‐derived peptide, rather than with 14‐3‐3, efficiently stabilize the 14‐3‐3/p65 complex and offer novel starting points for molecular glues., A novel concept for optimizing orthosteric protein–protein interaction (PPI) stabilization is reported. Increasing interactions with the protein partner that contributes less to the composite binding pocket of the stabilizer (NF‐κB, red surface) results in increased stabilization, whereas further enhancing the interaction with the dominant partner protein (14‐3‐3, white surface) does not contribute to the stabilizing effect.

We report on the fabrication of a rewritable and reprogrammable dual‐photoresponsive liquid crystalline‐based actuator containing an azomerocyanine dye that can be locally converted into the hydroxyazopyridinium form by acid treatment. Each dye absorbs at a different wavelength giving access to programmable actuators, the folding of which can be controlled by using different colors of light. The acidic patterning is reversible and allows the erasing and rewriting of patterns in the polymer film, giving access to reusable, adjustable soft actuators.

The decarboxylation of 2-cyano-2-phenylpropanoic acid is fast and quantitative when carried out in the presence of 1?molar equivalent of a [2]catenane composed of two identical macrocycles incorporating a 1,10-phenanthroline unit in their backbone. When decarboxylation is over, all of the catenane molecules have experienced large-amplitude motions from neutral to protonated catenane, and back again to the neutral form, so that they are ready to perform another cycle. This study provides the first example of the cyclic operation of a molecular switch at the sole expenses of the energy supplied by the substrate undergoing chemical transformation, without recourse to additional stimuli. Poetry in motion: Carboxylic acid 1 was found to be a convenient fuel for the operation of a molecular switch that moves under the influence of protonation-deprotonation steps. The cyclic motions of the catenane switch were induced solely by the chemical energy supplied by the decarboxylation of 1, without recourse to additional stimuli.

The induction of antigen-specific adaptive immunity exclusively occurs in lymphoid organs. As a consequence, the efficacy by which vaccines reach these tissues strongly affects the efficacy of the vaccine. Here, we report the design of polymer hydrogel nanoparticles that efficiently target multiple immune cell subsets in the draining lymph nodes. Nanoparticles are fabricated by infiltrating mesoporous silica particles (ca. 200 nm) with poly(methacrylic acid) followed by disulfide-based crosslinking and template removal. PEGylation of these nanoparticles does not affect their cellular association in vitro, but dramatically improves their lymphatic drainage in vivo. The functional relevance of these observations is further illustrated by the increased priming of antigen-specific T cells. Our findings highlight the potential of engineered hydrogel nanoparticles for the lymphatic delivery of antigens and immune-modulating compounds.

Give 'em structure: The presence of structuring elements in polymers that were functionalized with catalytic units resulted in a new class of enzyme mimics, which are only active in the folded state (see picture). The conformationally adaptive hydrophobic environment that surrounds the catalytic site allows the very efficient catalysis of an aldol reaction in water with Michaelis–Menten kinetics.

Light-induced self-assembly leads to the folding of synthetic random-coil polymers into highly stable single-chain polymeric chiral nanoparticles (see picture; green: side chains, blue: phenyl rings, red: nitrophenyl leaving groups). The folding of the polymer was aided by heating and cooling steps.

A beneficial virus: The hierarchical self-assembly of a three-component system consisting of single-stranded DNA (oligothymines; Tq), chromophores (G), and virus coat proteins (CP) leads to the formation of micrometer-long nanotubes (see picture). Tuning the interaction between the three components leads to the formation of structures with different length scales, and the chromophores within the nanotubes maintain the helical arrangement of the Tq–G template.

The internal organization of hybrid materials based on inorganic nanoparticles and p-conjugated polymers has a strong influence on their optoelectronic properties and affects the performance of devices with these materials as the active layer. For example, photovoltaic action in hybrid organic– inorganic materials requires intimate mixing of the individual components and also continuous pathways through both phases for the transport of electrons and holes towards an electrode. Furthermore, for the transport of electrons, holes, or excitations in hybrid materials, organization into domains with high aspect ratios (for example, rods, fibers, and tapes) is often preferred. An attractive approach to control the internal organization of hybrid materials is to use noncovalent, supramolecular interactions. The self-organization of organic molecules in solution into fiberlike structures, leading to gel formation, is well known. Recently, one-dimensional arrangements of metal nanoparticles have been obtained using gel composites, fibers, and templates of organic molecules. Noticeably, the combination of self-assembled, semiconducting p-conjugated organogelators and inorganic nanoparticles is unexplored and is of paramount importance from the viewpoint of hybrid optoelectronic materials. Herein, we report on a template approach in which metal nanoparticles are bound in a supramolecular manner to selfassembled, p-conjugated oligo(p-phenylenevinylene) (OPV) tapes, thus resulting in linear hybrid superstructures. Spectroscopic measurements highlight the electronic communication between the OPV tapes and the inorganic particles. The template chosen was an OPV derivative OPV1 (Scheme 1), which is a gelator of toluene that forms tapelike structures as a result of p–p stacking, hydrogen-bonding, and

Monitoring self-assembled objects: Optical studies and scanning confocal microscopy have been used to monitor intermolecular energy transfer (ENT) in mixed vesicles of donor/acceptor oligo(p-phenylene vinylene)s (OPVs) in water (see picture) over time. This probing of the ongoing exchange process between separate donor and acceptor vesicles proved that the properties of individual vesicles were different from those of the bulk solution.

Formaterialsscientists,anunderstandingoftheprinciples underlying the process of biomineralization holdsgreat promise for the design and synthesis of new inorganicand hybrid structures with yet unrealized properties. Thecentral concept in biomineralization research is that organ-izedbiomacromolecules,whichcontainwell-definedarraysoffunctional groups, control polymorph selection and theoriented nucleation of crystals by lowering the nucleationenergy of specific crystal faces.

Selective guest ejection: Up to eight guest molecules are assembled at the periphery of a third-generation dendrimer. Collision-induced dissociation mass spectrometry has demonstrated that the guests are removed very selectively in a one-by-one manner (see spectrum).

This work was supported by the Royal Netherlands Academy of Arts and Sciences, the Council for Chemical Sciences of the Netherlands Organization for Scientific Research (CW-NWO), and the Engineering and Physical Science Research Council (UK). L.M.H., C.D., and C.S. thank St John's College Cambridge, IRC Nanotechnology (Cambridge-UCL-Bristol), and the EPSRC (Advanced Research Fellowship), respectively, for financial assistance. D.B. is a senior research fellow of the Belgian National Science Foundation (FNRS). The authors thank Jeroen van Herrikhuyzen for the synthesis of MOPV4, Joost van Dongen for matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) MS measurements and E. Hennebicq and P. Leclère in Mons.

Left-handed-helical nanoropes are formed from higher-order self-assemblies of chiral aggregates during the gelation of a rigid π-conjugated oligo(p-phenylenevinylene) with remote chiral handles (see picture; R=C 12 H 25 ). The concentration- and temperature-dependent CD-signal changes observed for these assemblies are indicative of a helix transition. This process is reminiscent of the folding and unfolding of helical biological macromolecules.

Small-angle X-ray scattering measurements and UV/Vis titrations have been used to characterize a new water-soluble host¿–¿guest system based on oligoethyleneoxy-modified poly(propyleneimine) dendrimers. These experiments indicate that unique interactions between the host and guests lead to a specific location of the guests in the core of the dendrimers (see schematic representation).

Extremely effective cooperative effects operate during the formation of chiral stacks of C3-symmetrical molecules in alkane solvents (a molecule is depicted on the right). The sergeants-and-soldiers principles as well as chiral solvation lead to a preferred helical sense in the columnar aggregates. The amplification of chirality in dynamic systems shows the precision in aggregation.

More than 50 years after Otto Bayer's detailed description of [m,n]-polyurethanes, the first general synthesis of [n]-polyurethanes 1 is described. This series of aliphatic [n]-polyurethanes is synthesized by the in situ polymerization of the corresponding alpha,omega-isocyanato alcohol monomers, which in turn are made out of linear alpha,omega-amino alcohols and di-tert-butyltricarbonate. Polymers of high molecular weight possessing a uniform microstructure are obtained, while their melting points show a strong odd-even effect.

In two consecutive one-electron oxidations, oligopyrroles substituted with phenyl capping groups (PhPynPh, n = 2–4) can be oxidized reversibly to give stable cation radicals and dications. Spectroelectrochemical studies give direct evidence that diamagnetic p-dimers of cation radicals are formed in solution. Such dimers may be involved as charge carriers in conducting polypyrrole.