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International audience; This paper reports on the thermodynamics through mapping out temperature−concentration phase diagrams and the molecular structure and the morphology of binary organogels prepared with trisamide triarylamine (TATA) in tetrachloroethane and on their ternary thermoreversible hybrid gels formed with polyvinyl chloride (PVC). For low PVC contents, the TATA organogel moiety behaves as in the binary systems, while for higher PVC contents, the thermal behavior is significantly altered with the appearance of a nonvariant event. The molecular structure of the TATA assemblies is compared with that observed in the bulk solid state. Three molecular packings are observed in the bulk, whose crystalline lattices are tentatively derived. Structure I obtained after the crystallization−purification process is seen to transform at higher temperature into structure II. By cooling, structure III is obtained, which transforms reversibly into structure II on heating. The metastability of structure I leads one to contemplate the possible formation of molecular compounds during the crystallization− purification process in the presence of chlorinated solvents, the more so as the crystalline structures in the gels turn out to exhibit high similarities. Finally, the morphology observation reveals that the TATA fibrils and the PVC matrix can be well identified for low PVC contents, while for higher PVC contents, one essentially observes the TATA fibrils.

International audience; Amphiphilic imines prepared by condensation of a hydrophobic fragrance aldehyde with a hydrophilic amine derived from a hydrophilic poly(propylene oxide) and poly(ethylene oxide) diblock copolymer were investigated as cleavable surfactant profragrances in applications of functional perfumery. In water, the cleavable surfactants assemble into micelles that allow solubilization of perfume molecules that are not covalently attached to the surfactant. Dynamic headspace analysis on a glass surface showed that solubilized perfume molecules evaporated in a similar manner in the presence of the cleavable surfactant as compared with a noncleavable reference surfactant. Under application conditions, the cleavable surfactant imine hydrolysed to release the covalently linked fragrance aldehyde. The profragrances were stable during storage in aqueous media and upon dilution showed a blooming effect for the hydrolytical fragrance release and a more balanced performance of a solubilized perfume by retaining the more volatile fragrances and boosting the evaporation of the less volatile fragrances.

International audience; The detailed structure of active polymer gels built by integrating light-driven rotary molecular motors as reticulation units in polymer networks is discussed as a function of gel composition. Upon light-irradiation, the collective rotation of molecular motors is translated into the macroscopic contraction of the gels through polymer chains twisting. The major role of the characteristic ratio c/c* (c* being the overlap concentration of the polymer-motor conjugates before crosslinking) on the contraction efficiency is exploited. Combined small-angle neutron and X-ray scattering experiments reveal the importance of heterogeneities in the macroscopic contraction process: the mesh size of the network increases under irradiation in the whole range of c/c*, an increase that is maximal for c/c*=1; i.e. at higher contraction efficiency. Furthermore, the mesh size of the network reaches equilibrium within a short period of time, while the heterogeneiteis increase in size untill the end of the contraction process. Finally, the significant motorized twisting of polymer chains within the network allows to foresee the design of new storage energy systems.

International audience; A S6-symmetric triarylamine-based macrocycle (i.e. hexaaza[16]para-cyclophane), decorated with six lateral amide functions, is synthesized by a convergent and modular strategy. This macrocycle is shown to undergo supramolecular polymerization in o-dichlorobenzene, and its nanotubular structure is elucidated by a combination of spectroscopy and microscopy techniques, together with X-ray scattering and molecular modelling. Upon sequential oxidation, a spectroelectrochemical analysis of the supramolecular polymer suggests an extended electronic delocalization of charge carriers both within the macrocycles (through bond) and between macrocycles along the stacking direction (through space).

International audience; Despite their intrinsic hydrolysable character, imine bonds can become remarkably stable in water when self-assembled in amphiphilic micellar structures. In the present article, we systematically study some of these structures and the influence of various parameters that can be used to take control over their hydrolysis, including pH, concentration, position of the imine function in the amphiphilic structure, relative lengths of the linked hydrophilic and hydrophobic moieties. Thermodynamic and kinetic data lead us to the rational design of stable imines in water, partly based on the location of the imine function within the hydrophobic part of the amphiphile and on a predictable quantitative term that we define as the total hydrophilic-lipophilic balance (HLB). In addition, we show that such stable systems are also stimuli-responsive and therefore, of potential interest in trapping and releasing micellar components on demand.

International audience; Dilute solutions of electronically active molecules capable of irradiation-driven supramolecular self-assembly are studied by dynamic light scattering. We detect unusual well-defined oscillations in the long time range of the homodyne intensity correlation function for all solutions that were irradiated with white light prior to the measurements. The oscillation effect is attributed to the local laser-induced heating of the samples due to strongly enhanced absorption manifested by the supramolecular filaments. It is found that the oscillation frequency depends on the irradiation time, solution concentration, and the incident laser power, but is independent of the scattering angle. These observations are explained with a semi-quantitative theory relating the oscillation effect to thermo-gravitational convection flows generated by laser beam. The results suggest that the presence of such homodyne oscillations could be a sensitive probe for aggregation in many complex systems.

A clickable fullerene hexa-adduct scaffold has been functionalized with twelve triarylamine subunits. The light-triggered self-assembly of this molecular unit leads to 3D honeycomb-like structures with inner pores of around 10 nm diameter. Multiple grafting of triarylamine subunits onto a hard-core C60 unit increases the dimensionality of the self-assembly process by reticulating the 1D nanowires typically obtained from the supramolecular polymerization of triarylamine monomers.

International audience; The implementation of molecular machines in polymer science is of high interest to transfer mechanical motions from nanoscale to macroscale in order to access new kinds of active devices and materials. Toward this objective, thermodynamic and topological aspects need to be explored for reaching efficient systems capable of producing a useful work. In this paper we describe the branched polymerization of pH-sensitive bistable [c2] daisy chain rotaxanes by using copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (“click chemistry”). With this cross-linked topology, the corresponding materials in the form of chemical gels can be contracted and expanded over a large variation of volume (∼50%) by changing the protonation state of the system. HR-MAS 1H NMR and neutron scattering experiments reveal that this macroscopic response of the gels results from the synchronized actuation of the mechanical bonds at the molecular level.

In this paper we describe a diastereoselective synthesis of highly functionalized and optically pure Feringa's molecular motors. Two types of chemical functions are introduced on the upper and lower parts of the motor, and their orthogonality is investigated. The synthesis is performed on a gram scale and the diastereoisomers are easily separated by a straightforward column chromatography on silica gel. This general synthetic route is of particular interest to implement these molecular motors in devices and materials science.

Triarylamine molecules appended with crown-ethers or carboxylic moieties form self-assembled supramolecular channels within lipid bilayers. Fluorescence assays and voltage clamp studies reveal that the self-assemblies incorporating the crown ethers work as single channels for the selective transport of K+ or Rb+. The X-ray crystallographic structures confirm the mutual columnar self-assembly of triarylamines and crown-ethers. The dimensional fit of K+ cations within the 18-crown-6 leads to a partial dehydration and to the formation of alternating K+ cation-water wires within the channel. This original type of organization may be regarded as a biomimetic alternative of columnar K+-water wires observed for the natural KcsA channel. Supramolecular columnar arrangement was also shown for the triarylamine-carboxylic acid conjugate. In this latter case, stopped-flow light scattering analysis reveals the transport of water across lipid bilayer membranes with a relative water permeability as high as 17 μm s–1.

International audience; Precise control over molecular movement is of fundamental and practical importance in physics, biology, and chemistry. At nanoscale, the peculiar functioning principles and the synthesis of individual molecular actuators and machines has been the subject of intense investigations and debates over the past 60 years. In this review, we focus on the design of collective motions that are achieved by integrating, in space and time, several or many of these individual mechanical units together. In particular, we provide an in-depth look at the intermolecular couplings used to physically connect a number of artificial mechanically active molecular units such as photochromic molecular switches, nanomachines based on mechanical bonds, molecular rotors, and light-powered rotary motors. We highlight the various functioning principles that can lead to their collective motion at various length scales. We also emphasize how their synchronized, or desynchronized, mechanical behavior can lead to emerging functional properties and to their implementation into new active devices and materials

C3 -Symmetric triarylamine trisamides (TATAs), decorated with three norbornene end groups, undergo supramolecular polymerization and further gelation by π-π stacking and hydrogen bonding of their TATA cores. By using subsequent ring-opening metathesis polymerization, these physical gels are permanently crosslinked into chemical gels. Detailed comparisons of the supramolecular stacks in solution, in the physical gel, and in the chemical gel states, are performed by optical spectroscopies, electronic spectroscopies, atomic force microscopy, electronic paramagnetic resonance spectroscopy, X-ray scattering, electronic transport measurements, and rheology. The results presented here clearly evidence that the core structure of the functional supramolecular polymers can be precisely retained during the covalent capture whereas the mechanical properties of the gels are concomitantly improved, with an increase of their storage modulus by two orders of magnitude.

Upon cooling insolution, chiral triarylamine tris-amide unimers produce organogels by stacking into helical supramolecular polymers, which subsequently bundle into larger fibers. Interestingly, circular dichroism, vibrational circular dichroism, and AFM imaging of the chiral self-assemblies revealed that monocolumnar P-helical fibrils formed upon fast cooling, whereas bundled M-superhelical fibers formed upon slow cooling. The mechanistic study of this structural bifurcation reveals the presence of a strong memory effect, reminiscent of a complex stepwise combination of primary and secondary nucleation-growth processes. These results highlight the instrumental role of sequential self-assembly processes to control supramolecular architectures of multiple hierarchical order.

International audience; Triarylamine molecules and triarylamine-based covalent polymers have been extensively investigated for more than 60 years in academics and industry because of their intriguing electronic and optical characteristics. However, despite the profusion of studies made on these derivatives, only very recently have the first examples of supramolecular polymers based on the triarylamine motif been described in the literature. Specifically, our research group has shown that, by adding supplementary hydrogen bonding moieties such as amide functions in their periphery, it becomes possible to tightly pack triarylamine molecules in columnar supramolecular stacks presenting a collinear arrangement of their central nitrogen atoms. These supramolecular polymers can self-assemble into various soft hierarchical structures such as helical fibers, nanorods, nanospheres, and nanoribbons in the sol and in the gel states, into liquid-crystalline mesophases, and into highly organized supramolecular frameworks and single crystals thereof.Interestingly, the associated supramolecular polymerization mechanism involves a nucleation step of high activation energy, which requires the flattening of the triarylamine core. Because of this singularity and although dependent on the precise chemical nature of the building blocks, it has been demonstrated that their supramolecular polymerization can be triggered by original tools, such as light irradiation or electrochemistry, and that it can display autocatalytic growth behaviors, remarkably strong amplifications of chirality, and complex and competing thermodynamic and kinetic self-assembly pathways.Further, from a functional point of view, it has been highlighted that a partial oxidation of the triarylamine molecules results in an enhanced through-space delocalization of the charge carriers along the π–π stacked supramolecular polymers, a feature that confers to these nanowires exceptional transport properties. Upon increasing the charge carrier concentration, the electronic nature of these soft materials can be switched from semiconducting to metallic behavior, and the presence of highly delocalized unpaired electrons in supramolecular polaronic band structures has been further exploited to implement plasmonic properties within subwavelength organic interconnects and microscopic optical waveguides.Finally, by making use of the unusual dynamics and functions of triarylamine-based nanostructures, it becomes possible to precisely address their self-construction within confined environments or within nano- and micrometer scale devices. This has been demonstrated for instance between nanoparticles and between electrodes, inside inorganic nanopores, and inside phospholipid bilayers, as well as at the liquid–liquid interface. Such a meeting point between bottom-up and top-down technologies is of high interest to envision further developments and applications for this entirely new class of supramolecular polymers, which combine a unique relationship between their structures, their dynamics, and their subsequent emerging functional properties.

The networking of individual artificial molecular motors into collective actuation systems is a promising approach for the design of active materials working out of thermodynamic equilibrium. Here, we report the first mechanical studies on active polymer gels built by integrating light-driven rotary molecular motors as reticulation units in polymer networks. We correlate the volume ratio before and after light irradiation with the change of the elastic modulus, and we reveal the universal maximum mechanical efficiency of such gels related to their critical overlap concentration before chemical reticulation. We also show the major importance of heterogeneities in the macroscopic contraction process and we confirm that these materials can increase their internal energy by the motorized winding of their polymer chains.

International audience; Hybrid thermoreversible gels have been prepared from polyvinyl chloride (PVC) and tri-aryl tri-amines organogelators (TATA-C11) in bromobenzene. A thermodynamic investigation by DSC has shown that the TATA-C11 formation and melting temperatures are not altered by the presence of PVC chains, nor are the formation and melting enthalpies. Scanning electron microscopy observations have revealed as each network are clearly distinguished, so that the hybrid gel is simply a combination at the micron level of both original gels. X-ray diffraction experiments have shown that the TATA-C11 structure in bromobenzene differs from its solid state, and is rather reminiscent of a hexatic phase, possibly due to the occurrence of a molecular compound. The structure of the TATA-C11 moiety does not change in the hybrid gel. Finally, the rheological properties have been studied. It is observed that the modulus of the hybrid gel greatly exceeds the Voigt's upper limit (larger than a simple additivity of the moduli). This effect is examined in the light of a possible de-solvation of the amorphous part of the PVC fibrils (de-plasticization).

Bistable [ c2]daisy chain rotaxanes represent a particularly intriguing class of interlocked molecules that can produce internal sliding movements with a net contraction or extension at the single-molecule level. These nanometric motions show some analogies with the sliding motions of actin and myosin filaments in sarcomeres, and this is why [ c2]daisy chain rotaxanes have been also named as “molecular muscles,” as their first synthesis in 2000. In this minireview, the authors discuss the recent history of these molecules, their modular chemical structures, and the various synthetic pathways described in the literature to access them. The authors also detail how their internal motions can be controlled and characterized by a number of chemical and physical tools. The authors finally show that their integration within polymers and materials can give access to synchronized motions and amplifications up to the macroscopic scale. Overall, the numerous examples that have been described in the literature to date demonstrate that this family of molecules has already strongly influenced the entire field of research on artificial molecular machines, and has the potential to be implemented as actuators working at all scales, from nanometric-switchable devices to mechanically active soft matter materials.

A dendritic unit based on a benzenetricarboxamide core and three triarylamine arms has been synthesized and characterized. Self-assembled micrometric crystalline fibers can be formed in various organic solvents. This derivative has also been studied in chlorinated solvents upon visible light stimulation, giving rise to self-assembled fibers with triarylammonium cations trapped in their supramolecular structure. Overall, this work enlarges the scope of chemical modifications that can be made on triarylamine cores to produce doped supramolecular architectures with potential interests for optoelectronic materials.

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.

A family of triarylamine-fullerene conjugates has been synthesized and shown to self-assemble upon light stimulation in chlorinated solvents. This light-induced process primarily involves excitation of triarylamine derivatives, which then oxidize and stack with their neutral counterparts to form charge transfer complexes in the form of p-conducting channels, while fullerenes are consequently enforced in coaxial n-conducting columnar arrangements. These supramolecular heterojunctions can be organized over very long distances in micrometric fibers when a controlled amount of photons is provided from a white light source to initiate the process. Surprisingly, when sunlight or UV light is used instead, the nanostructuration leads to monodisperse spherical objects due to the nature of the nucleation-growth process involved in the stacks formation. This control over the supramolecular morphology of organic self-assemblies using the nature of light is of general interest for the design of functional responsive materials.

A logic gate based on a bistable [c2] daisy chain rotaxane decorated with lateral triarylamine units is described, giving rise to an INHIBIT logic function using proton concentration and light as inputs, and producing dual color change and supramolecular self-assembly as outputs.

International audience; The implementation of artificial molecular machines in polymer science is an important objective that challenges chemists and physicists in order to access an entirely new class of smart materials. To design such systems, the amplification of a mechanical actuation from the nanoscale up to a macroscopic response in the bulk material is a central issue. In this article we show that bistable [c2]daisy chain rotaxanes (i.e. molecular muscles) can be linked into mainchain Upy-based supramolecular polymers. We then reveal by an in depth quantitative study that the pH actuation of the mechanically active rotaxane at the nanoscale influences the physical reticulation of the polymer chains by changing the supramolecular behavior of the Upy units. This nano-actuation within the local structure of the main chain polymer results in a mechanically controlled sol-gel transition at the macroscopic level.

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.

The study of supramolecular polymers in the bulk, in diluted solution, and at the solid–liquid interface has recently become a major topic of interest, going from fundamental aspects to applications in materials science. However, examples of supramolecular polymers at the liquid–liquid interface are mostly unexplored. Here, we describe the supramolecular polymerization of triarylamine molecules and their light-triggered organization at a chloroform–water interface. The resulting interfacial nematic layer of these 1D supramolecular polymers is further used as a template for the precise alignment of spherical gold nanoparticles coming from the water phase. These hybrid thin films are spontaneously formed in a single process, without chemical prefunctionalization of the metallic nanoparticles, and their ordering is improved by centrifugation. The resulting polymer chains and strings of nanoparticles can be co-aligned with high anisotropy over very large distances. By using a combination of experimental and theoretical investigations, we decipher the full sequence of this oriented self-assembly process. In such a highly anisotropic configuration, electron energy loss spectroscopy reveals that the self-assembled nanoparticles behave as plasmonic waveguides.

International audience; In this article, the dynamic structure of complex supramolecular polymers composed of bistable [c2]daisy chain rotaxanes as molecular machines that are linked by ureidopyrimidinones (Upy) as recognition moieties was studied. pH actuation of the integrated mechanically active rotaxanes controls the contraction/extension of the polymer chains as well as their physical reticulation. Small-angle neutron and X-ray scattering were used to study in-depth the nanostructure of the contracted and extended polymer aggregates in toluene solution. The supramolecular polymers comprising contracted nanomachines were found to be equilibrium polymers with a mass that is concentration dependent in dilute and semidilute regimes. Surprisingly, the extended polymers form a gel network with a crystal-like internal structure that is independent of concentration and reminiscent of a pearl-necklace network.

Even though the macrolides of the iejimalide family are of marine origin, whereas those of the archazolid series derive from terrestrial myxobacteria, a comparison of their constitution, stereochemistry, and biological activity suggests that these natural products are close structural and functional relatives. Guided by this perception, compound 5 was prepared, which hybridizes the macrolactone core of iejimalide B (2) with the tail of archazolid A (3). The cytotoxicity profile of this chimera, as determined with a panel of 12 human cancer cell lines, corresponds to that of the parent compound 2, although its potency is lower. This outcome may be interpreted on the basis of molecular dynamics calculations, which suggest that the low energy conformations of 2 and 5 are similar but the energetic barriers between the relevant conformers are distinctly higher for the hybrid structure. The synthesis of 5 hinged on a regioselective functionalization of 2,4-dibromothiazole 6, a highly selective CBS-reduction of ketone 8, a Suzuki cross coupling of vinyl boronate 17 with the elaborate alkenyl iodide 16, and a productive closure of the macrocycle by RCM, which requires the selective activation of two out of eight double bonds present in the cyclization precursor 20 by the second-generation Grubbs catalyst 21.

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.

A concise and convergent total synthesis of the highly cytotoxic marine natural products iejimalide A-D (1-4) is reported, which relies on an effective ring-closing metathesis (RCM) reaction of a cyclization precursor containing no less than 10 double bonds. Because of the exceptional sensitivity of this polyunsaturated intermediate and its immediate precursors toward acid, base, and even gentle warming, the assembly process hinged upon the judicious choice of protecting groups and the careful optimization of all individual transformations. As a consequence, particularly mild protocols for Stille as well as Suzuki reactions of elaborate coupling partners have been developed that hold considerable promise for applications in other complex settings. Moreover, a series of non-natural "iejimalide-like" compounds has been prepared, differing from the natural lead in the polar head groups linked to the macrolide's N-terminus. With the aid of these compounds it was possible to uncover the hitherto unknown effect of iejimalide and analogues on the actin cytoskeleton. Their capacity to depolymerize this microfilament network rivals that of the latrunculins which constitute the standard in the field. Structural modifications of the peptidic terminus in 2 are thereby well accommodated, without compromising the biological effects. The iejimalides hence constitute an important new class of probe molecules for chemical biology in addition to their role as promising lead structures for the development of novel anticancer agents.

We have investigated the self-assembly in water of molecules having a single hydrophobic bis-urea domain linked to different hydrophilic functional side chains, i.e., bioactive peptidic residues and fluorescent cyanine dyes. By using a combination of spectroscopy, scattering, and microscopy techniques, we show that each one of these molecules can individually produce well-defined nanostructures such as twisted ribbons, two-dimensional plates, or branched fibers. Interestingly, when these monomers of different functionalities are mixed in an equimolar ratio, supramolecular copolymers are preferred to narcissistic segregation. Radiation scattering and imaging techniques demonstrate that one of the molecular units dictates the formation of a preferential nanostructure, and optical spectroscopies reveal the alternated nature of the copolymerization process. This work illustrates how social self-sorting in H-bond supramolecular polymers can give straightforward access to multifunctional supramolecular copolymers.

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.

Making molecular machines that can be useful in the macroscopic world is a challenging long-term goal of nanoscience. Inspired by the protein machinery found in biological systems, and based on the theoretical understanding of the physics of motion at the nanoscale, organic chemists have developed a number of molecules that can produce work by contraction or rotation when triggered by various external chemical or physical stimuli. In particular, basic molecular switches that commute between at least two thermodynamic minima and more advanced molecular motors that behave as dissipative units working far from equilibrium when fuelled with external energy have been reported. However, despite recent progress, the ultimate challenge of coordinating individual molecular motors in a continuous mechanical process that can have a measurable effect at the macroscale has remained elusive. Here, we show that by integrating light-driven unidirectional molecular rotors as reticulating units in a polymer gel, it is possible to amplify their individual motions to achieve macroscopic contraction of the material. Our system uses the incoming light to operate under far-from-equilibrium conditions, and the work produced by the motor in the photostationary state is used to twist the entangled polymer chains up to the collapse of the gel. Our design could be a starting point to integrate nanomotors in metastable materials to store energy and eventually to convert it.

By using a combination of experimental and theoretical tools, we elucidate unique physical characteristics of supramolecular triarylamine nanowires (STANWs), their packed structure, as well as the entire kinetics of the associated radical-controlled supramolecular polymerization process. AFM, small-angle X-ray scattering, and all-atomic computer modeling reveal the two-columnar "snowflake" internal structure of the fibers involving the π-stacking of triarylamines with alternating handedness. The polymerization process and the kinetics of triarylammonium radicals formation and decay are studied by UV-vis spectroscopy, nuclear magnetic resonance and electronic paramagnetic resonance. We fully describe these experimental data with theoretical models demonstrating that the supramolecular self-assembly starts by the production of radicals that are required for nucleation of double-columnar fibrils followed by their growth in double-strand filaments. We also elucidate nontrivial kinetics of this self-assembly process revealing sigmoid time dependency and complex self-replicating behavior. The hierarchical approach and other ideas proposed here provide a general tool to study kinetics in a large number of self-assembling fibrillar systems.

Organic materials exhibiting metallic behavior are promising for numerous applications ranging from printed nanocircuits to large area electronics. However, the optimization of electronic conduction in organic metals such as charge-transfer salts or doped conjugated polymers requires high crystallinity, which is detrimental to their processability. To overcome this problem, the combination of the electronic properties of metal-like materials with the mechanical properties of soft self-assembled systems is attractive but necessitates the absence of structural defects in a regular lattice. Here we describe a one-dimensional supramolecular polymer in which photoinduced through-space charge-transfer complexes lead to highly coherent domains with delocalized electronic states displaying metallic behavior. We also reveal that diffusion of supramolecular polarons in the nanowires repairs structural defects thereby improving their conduction. The ability to access metallic properties from mendable self-assemblies extends the current understanding of both fields and opens a wide range of processing techniques for applications in organic electronics.

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

[chemical reaction: see text]. An expedient synthesis of (-)-pochonin A is reported (seven steps). This natural product is closely related to radicicol and was shown to be a 90 nM inhibitor of HSP90.

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.

Pumping iron: Double-threaded rotaxanes can be linked to coordination units and polymerized in the presence of iron or zinc ions. pH modulation triggers cooperative contractions (or extensions) of the individual rotaxanes, thus resulting in an amplified motion of the muscle-like supramolecular chains with changes of their contour lengths of several micrometers (see picture).

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

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

The structural and dynamical properties of dilute aqueous solutions of poly(ethylene glycol)-perylene diimides (PEG(n)-PDI) have been investigated by means of static and dynamic light scattering, TEM microscopy, and small-angle X-ray scattering experiments. The amphiphilic PEG(n)-PDI molecules first self-assemble into stable and compact primary stacks of a few units of planar PDI through hydrophobic and π-π interactions. These primary stacks subsequently arrange in large and globular aggregates of typically 100-250 nm via weak PEG chain interpenetration. Surprisingly, the scattered electric field autocorrelation function g((1))(q,t) measured by dynamic light scattering evolves over very long periods of times (several months) and up to a bimodal distribution. The fast relaxation mechanism is associated to the diffusion of free primary stacks, whereas the slower relaxation still indicates the presence of large self-assemblies. Kinetic experiments show that the large supramolecular aggregates slowly release the free primary stacks whose proportion increases with time. This dissociation depends on several parameters such as PEG side chain length, total concentration, and shaking.

International audience; The construction of soft and processable organic material able to display metallic conduction properties—a large density of freely moving charges—is a major challenge for electronics. Films of doped conjugated polymers are widely used as semiconductor devices, but metallic-type transport in the bulk of such materials remains extremely rare. On the other hand, single-walled carbon nanotubes can exhibit remarkably low contact resistances with related large currents, but are intrinsically very difficult to isolate and process. Here, we describe the self-assembly of supramolecular organic nanowires between two metallic electrodes, from a solution of triarylamine derivative, under the simultaneous action of light and electric field triggers. They exhibit a combination of large conductivity values (>5 × 103 S m−1) and a low interface resistance (

Iejimalide B (2) is the most promising member of a small family of marine polyene macrolides endowed with remarkably selective activity against human cancer cell lines. As this product, however, is hardly available from the natural sources, a detailed evaluation requires the development of an efficient and practical synthetic approach. This challenge has now been met by adapting the first total synthesis of 2 previously reported by our group to the needs of high material throughput. Redesigning the access routes to the five required building blocks in combination with a careful optimization of the fragment coupling processes provided gram amounts of this valuable compound in a sequence of no more than 16 linear steps with an overall yield of about 7%. Key elements of the successful strategy include: i) three hydrostannylation processes of elaborate terminal alkynes with "lower order" stannyl cuprates, ii) a Brown allylation, a Noyori transfer hydrogenation, and a Marshall propargylation to set the chiral centers at C9, C17, C22 and C23, and iii) a modified Takai-Utimoto olefination for the preparation of the very labile skipped 1,4-diene flanking the ester group. The assembly process benefited from a particularly mild protocol for the Stille cross-coupling previously developed in this laboratory, which clearly outperformed the alternative Suzuki reaction in terms of yield and scalability. The 24-membered macrocyclic frame was forged by a remarkably selective ring-closing metathesis reaction (RCM), in which two out of the ten double bonds present in the cyclization precursor were selectively activated with the aid of a second-generation Grubbs catalyst.

Systematic variation of all substructures embedded into the framework of iejimalide B (2) led to a panel of synthetic analogues of this polyunsaturated macrolide, featuring structural modifications that are not accessible by derivatization of the natural lead compound itself. The assessment of the cytotoxicity of these compounds with the aid of a monolayer proliferation assay (12 human tumor cell lines in vitro) as well as a colony formation assay (24 human tumor xenografts ex vivo) revealed the exceptional potency of 2 and several of its synthetic congeners, with IC(50) values in the picomolar range for the most sensitive cell lines. Whereas structural modifications of the macrocycle or of the side chain generally lead to a decrease in activity, changes of the peptidic terminus are not only well accommodated but engender increased tumor selectivity as well. 2 and two of the most promising analogues were selected for in vivo studies in mice, in which their activity against human tumor xenografts of breast cancer (MAXF 401) and prostate cancer (PRXF PC-3M) was tested. In contrast to a previous report in the literature however, which had claimed in vivo activity for the parent iejimalides, these tests did not show a significant therapeutic effect against the chosen solid tumors upon intraperitoneal administration.

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.

International audience; Let there be more light: Triarylamine-based building blocks respond to visible-light exposure by the formation of cationic radicals that hierarchically self-assemble into molecular wires, which in turn combine within larger fibers (see picture). The stimuli-responsive supramolecular scaffold, which is created by charge transfer and reversibly broken up by heating, prevents the quenching of holes within the wires.