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An acid-base switchable [c2]daisy chain rotaxane terminated with two 2,6-diacetylamino pyridine units has been self-assembled with a bis(uracil) linker. The complementary hydrogen-bond recognition patterns, together with lateral van der Waals aggregations, result in the hierarchical formation of unidimensional supramolecular polymers associated in bundles of muscle-like fibers. Microscopic and scattering techniques reveal that the mesoscopic structure of these bundles depends on the extended or contracted states that the rotaxanes show within individual polymer chains. The observed local dynamics span over several length scales because of a combination of supramolecular and mechanical bonds. This work illustrates the possibility to modify the hierarchical mesoscopic structuring of large polymeric systems by the integrated actuation of individual molecular machines.

We have synthesized a series of triarylamine-cored molecules equipped with an adjacent amide moiety and dendritic peripheral tails in a variety of modes. We show by (1) H NMR and UV/Vis spectroscopy that their supramolecular self-assembly can be promoted in solution upon light stimulation and radical initiation. In addition, we have probed their molecular arrangements and mesomorphic properties in the bulk by integrated studies on their film state by using differential scanning calorimetry (DSC), variable-temperature polarizing optical microscopy (VT-POM), variable-temperature X-ray diffraction (VT-XRD), and atomic force microscopy (AFM). Differences in the number and the disposition of the peripheral tails significantly affect their mesomorphic properties associated with their lamellar- or columnar-packed nanostructures, which are based on segregated stacks of the triphenylamine cores and the lipophilic/lipophobic periphery. Such structural tuning is of interest for implementation of these soft self-assemblies as electroactive materials from solution to mesophases.

Artificial molecular machines are able to produce and exploit precise nanoscale actuations in response to chemical or physical triggers. Recent scientific efforts have been devoted to the integration, orientation, and interfacing of large assemblies of molecular machines in order to harness their collective actuations at larger length scale and up to the generation of macroscopic motions. Making use of such "hierarchical mechanics" represents a fundamentally new approach for the conception of stimuli-responsive materials. Furthermore, because some molecular machines can function as molecular motors-which are capable of cycling a unidirectional motion out of thermodynamic equilibrium and progressively increasing the work delivered to their environment-one can expect unique opportunities to design new kinds of mechanically active materials and devices capable of autonomous behavior when supplied by an external source of energy. Recently reported achievements are summarized, including the integration of molecular machines at surfaces and interfaces, in 3D self-assembled materials, as well as in liquid crystals and polymer materials. Their detailed functioning principles as well as their functional properties are discussed along with their potential applications in various domains such as sensing, drug delivery, electronics, optics, plasmonics, and mechanics.

Supramolecular organic electronics rests on the use of bottom-up chemical self-assembly processes in order to design conducting components on the 5-100 nm scale. The challenges in this field are both the construction of 1D-nanostructures displaying optimized transport properties and their precise connections to electrodes. The present Research News highlights important advances in such materials regarding their electrical performances, from semiconductors to organic metals, but also regarding their processability. In particular, by externally controlling light-responsive supramolecular polymerization processes, and by using appropriate methods of casting with an applied electric field, it becomes possible to pre-determine the accurate positioning of organic interconnects within patterned nano-circuitry. These strategies using external stimuli to obtain addressability, thus hold promising alternatives to other conducting materials such as carbon nanotubes for further technological applications in nanosciences.

A multitasking C-silylation strategy using the readily available compound 26 as a surrogate for cinnamic acid represents the key design element of a total synthesis of all known members of the ipomoeassin family of resin glyosides. This protecting group maneuver allows the unsaturated acids decorating the glucose subunit of the targets to be attached at an early phase of the synthesis, prevents their participation in the ruthenium-catalyzed ring-closing metathesis (RCM) used to form the macrocyclic ring, and protects them against reduction during the hydrogenation of the resulting cycloalkene over Wilkinson's catalyst. As the C-silyl group can be concomitantly removed with the O-TBS substituent using tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) in acetonitrile, no separate protecting group manipulations were necessary in the final stages, thus contributing to a favorable overall "economy of steps". In addition to the naturally occurring ipomoeassins, a small set of synthetic analogues has also been prepared by "diverted total synthesis". The cytotoxicity of these compounds was assayed with two different cancer cell lines. The recorded data confirm previous findings that the acylation- and oxygenation pattern of these amphiphilic glycoconjugates is highly correlated with their biological activity profile. Ipomoeassin F turned out to be the most promising member of the series, showing IC(50) values in the low nanomolar range.

Pochonins A-F were recently characterized as six new members of the naturally occurring family of 14-membered resorcylic acid lactones. As there are a high number of ATPase and kinase inhibitors among natural resorcylic lactones, a library based on the pochonin scaffold, with five points of diversity, was prepared which includes diversity beyond that of the natural analogues. The library was synthesized by using solid-supported reagents amenable to automation. Testing the library for its inhibition against a panel of 24 kinases at 10 microM afforded a14 % hit rate. These results demonstrate the potential of the resorcylides towards the inhibition of therapeutically relevant kinases.

A modular synthesis for pochonin C and radicicol is reported. The two natural products were prepared in seven and eight steps, respectively, from three readily available fragments. Alternative syntheses of these compounds were achieved using a combination of polymer-bound reagents and solid phase reactions. The conformation of the two natural products was studied and compared by using 2D NMR spectroscopy.

Back to its origins: Pochonin C was synthesized in 11 steps from the four fragments shown in the scheme. This asymmetric synthesis and the conversion of pochonin C into radicicol defines the configuration at the center bearing the chlorine atom as S. Ipc=isopenocampheyl, PG=protecting group.

Because of their recent interest towards dynamic combinatorial systems, chemists have to challenge their capacity to analyse complex mixtures of components exchanging their molecular fragments over time. Here we present, by a selection of practical examples from the literature, how chromatographic, spectroscopic, and microscopic techniques, as well as theoretical modelling and statistical data treatment, are instrumental in this new research area which is of significance at the interfaces with molecular biology and materials science.

Review: report on a synthetic strategy that allows the separation of enantiomerically ure planar chiral rotaxanes; 10 refs.

Thanks to their intrinsic network topologies, dynamic combinatorial libraries (DCLs) represent new tools for investigating fundamental aspects related to self-organization and adaptation processes. Very recently the first examples integrating self-replication features within DCLs have pushed even further the idea of implementing dynamic combinatorial chemistry (DCC) towards minimal systems capable of self-construction and/or evolution. Indeed, feedback loop processes – in particular in the form of autocatalytic reactions – are keystones to build dynamic supersystems which could possibly approach the roots of “Darwinian” evolvability at mesoscale. This topic of current interest also shows significant potentialities beyond its fundamental character, because truly smart and autonomous materials for the future will have to respond to changes of their environment by selecting and by exponentially amplifying their fittest constituents.

The dynamic processes in self-assemblies are involved in numerous domains that span throughout the modern aspects of chemical sciences, going from fundamental investigations into the origin of life to the most striking technological applications in medicine or electronics. This chapter aims at providing the reader with a brief overview of the concepts that link chemical reactivity with dynamic templates and catalysts made of large supramolecular assemblies. Specifically, we discuss kinetic and thermodynamic aspects of selected examples depending on (i) the nature of the matrix — that is, micelles, vesicles, liquid crystals, and gels; (ii) the nature of their constituents — that is, surfactants, block copolymers, bioactive macromolecules; and (iii) the nature of the chemical transformations that are performed — that is, reaction of small organic molecules, biomolecules, polymerizations, nanoparticle formation, and also reactions that involve the constituents of the matrix themselves as observed, for instance, in self-reproducing systems. In each section, we combine original papers that paved the field together with more recent works of particular interest; several reviews are also referenced to help in accessing a more comprehensive literature. Keywords: self-assembly; supramolecular chemistry; micelles; vesicles; surfactants; block copolymers; peptides; liquid crystals; gels; mesophases; nanostructuration; nanoreactors; materials synthesis; catalysis; polymerization; self-replication; dynamic combinatorial chemistry; chemical evolution