A Cu\u3csup\u3eI\u3c/sup\u3e-based metallo-supramolecular gel-like material built from a library of oligomeric ligands featuring exotopic 1,10-Phenanthroline units

\u3cp\u3eA 22-membered cyclic alkene C\u3csub\u3e1\u3c/sub\u3e incorporating an exotopic 1,10-phenanthroline nucleus in the ring skeleton has been synthesized and subjected to ring-opening metathesis polymerization (ROMP) in dilute dichloromethane solution at varying monomer concentrations (c\u3csub\u3emon\u3c/sub\u3e). The resultant libraries of macrocyclic oligomers were used as ligands for the generation of main-chain metal-ligand oligomeric/polymeric complexes taking advantage of the strong affinity of 1,10-phenanthroline derivatives for Cu\u3csup\u3eI\u3c/sup\u3e. The formation of a gel-like material only upon addition of [Cu(CH\u3csub\u3e3\u3c/sub\u3eCN)\u3csub\u3e4\u3c/sub\u3e]PF\u3csub\u3e6\u3c/sub\u3e to the most concentrated library (c\u3csub\u3emon\u3c/sub\u3e = 60 mM) was explained as arising from the presence of significant amounts of trimeric and higher oligomeric macrocycles C\u3csub\u3ei\u3c/sub\u3e (i ≥ 3), acting as cross-linking components. A gel-like material has been obtained by exo coordination of Cu\u3csup\u3eI\u3c/sup\u3e to the phenanthroline moieties of a library of multitopic cyclic ligands.\u3c/p\u3

Tandem catalysis in multicomponent solvent-free biofluids

\u3cp\u3eEnzymes are widely employed to reduce the environmental impact of chemical industries as biocatalysts improve productivity and offer high selectively under mild reaction conditions in a diverse range of chemical transformations. The poor stability of biomacromolecules under reaction conditions is often a critical bottleneck to their application. Protein engineering or immobilization onto solid substrates may remedy this limitation but, unfortunately, this is often at the expense of catalytic potency or substrate specificity. In this work, we show that the combinatorial approach of chemical modification and supramolecular nanoencapsulation can endow mechanistically diverse enzymes with apparent extremophilic behavior. A protein-polymer surfactant core-shell architecture facilitates construction of increasingly complex biofluids from individual biosynthetic components, each of which retain biological activity at hydration levels almost two orders of magnitude below solvation. The herein constructed multifunctional biofluids operate in tandem up to 150 °C and in the total absence of solvent under apparent diffusional mass-transport limitation. The biosynthetic promotion of extremophilic traits for enzymes with diverse catalytic motions and chemical functions highlights the extraordinary capacity for a viscous surfactant milieu to replace both hydration and bulk waters.\u3c/p\u3

Coupling of the decarboxylation of 2-Cyano-2-phenylpropanoic acid to large-amplitude motions:a convenient fuel for an acid-base-operated molecular switch

\u3cp\u3eThe decarboxylation of 2-cyano-2-phenylpropanoic acid is fast and quantitative when carried out in the presence of 1molar 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.\u3c/p\u3

Supramolecular polymerization of a ureidopyrimidinone-based [2]catenane prepared via ring-closing metathesis

\u3cp\u3eThe synthesis of a Sauvage-type [2]catenane featuring a quadruple hydrogen bonding ureidopyrimidinone (UPy) motif in each ring was reported. Intermolecular dimerization of the UPy motifs induces the hydrogen-bond-driven supramolecular polymerization of the [2]catenane monomer, thereby creating a linear polymer consisting of both hydrogen bonding and mechanical bonds. As the rings in the UPy catenane are asymmetric, two stereoisomers can be formed upon catenation, that is, with the phenanthroline moieties oriented +90° or -90° with respect to each other. Based on the phenanthroline-Cu(I) and ring-closing metathesis (RCM) approach, we first devised a synthetic procedure for the synthesis of the UPy-based catenane. Here, phenanthroline was first functionalized with phenol moieties in a two-step approach with an overall yield of 46%. The resulting biphenol 3 was then alkylated in a statistical manner with a mixture of 4-bromobut-1-ene and t-Boc-protected bromide resulting in t-Boc-protected compound. The results show that protection of the UPy motifs is necessary for this reaction to reach completion. Analysis of the unprotected UPy catenane by \u3csup\u3e1\u3c/sup\u3eH NMR revealed the formation of UPy-UPy dimers and significant broadening of the signals, both in presence and absence of Cu(I). \u3c/p\u3

Directing the solid-state organization of racemates via structural mutation and solution-state assembly processes

\u3cp\u3eChirality plays a central role in biomolecular recognition and pharmacological activity of drugs and can even lead to new functions such as spin filters. Although there have been significant advances in understanding and controlling the helical organization of enantiopure synthetic molecular systems, rationally dictating the assembly of mixtures of enantiomer (including racemates) is nontrivial. Here we demonstrate that a subtle change in molecular structure coupled with the understanding of assembly processes of enantiomers and racemates, in both dilute solution and concentrated gels, acts as a stepping stone to rationally control the organization in the solid-state. We have studied trans-1,2-disubstituted cyclohexanes as model systems with carboxamide, thioamide, and their combination as functional groups. On comparing the gelation propensity of individual enantiomers and racemates, we find that racemates of carboxamide, thioamide, and their combination adopt self-sorting, coassembly, and mixed organization, respectively. Remarkably, these modes of assembly of racemates were also retained in solid-state. These results point out that studying the solution-phase assembly is a key link for connecting molecular structure with the assembly in the solid-state, even for racemates.\u3c/p\u3

Peptide-driven charge-transfer organogels built from synergetic hydrogen bonding and pyrene–naphthalenediimide donor–acceptor interactions

\u3cp\u3eThe peptide-driven formation of charge transfer (CT) supramolecular gels featuring both directional hydrogen-bonding and donor–acceptor (D-A) complexation is reported. Our design consists of the coassembly of two dipeptide–chromophore conjugates, namely diphenylalanine (FF) dipeptide conveniently functionalized at the N-terminus with either a pyrene (Py-1, donor) or naphthalene diimide (NDI-1, acceptor). UV/Vis spectroscopy confirmed the formation of CT complexes. FTIR and \u3csup\u3e1\u3c/sup\u3eH NMR spectroscopy studies underlined the pivotal role of hydrogen bonding in the gelation process, and electronic paramagnetic resonance (EPR) measurements unraveled the advantage of preorganized CT supramolecular architectures for charge transport over solutions containing non-coassembled D and A molecular systems.\u3c/p\u3

Mesoscopic helical architectures:Via self-assembly of porphyrin-based discotic systems

\u3cp\u3eMesoscopic super-helices with preferred helicity have been serendipitously formed from the self-assembly of electroactive extended core discotic molecules. The investigation at dilute concentrations reveals intramolecular hydrogen-bonding and π-π stacking interactions as the driving force of the chiral self-assembly at different length scales.\u3c/p\u3

Copper(i)-induced amplification of a [2]catenane in a virtual dynamic library of macrocyclic alkenes

Olefin cross-metathesis of diluted dichloromethane solutions (=0.15 M) of the 28-membered macrocyclic alkene C1, featuring a 1,10-phenanthroline moiety in the backbone, as well as of catenand 1, composed of two identical interlocked C1 units, generates families of noninterlocked oligomers Ci. The composition of the libraries is strongly dependent on the monomer concentration, but independent of whether C1 or 1 is used as feedstock, as expected for truly equilibrated systems. Accordingly, the limiting value 0.022 M approached by the equilibrium concentration of C1 when the total monomer concentration approaches the critical value, as predicted by the Jacobson-Stockmayer theory, provides a reliable estimate of the thermodynamically effective molarity. Catenand 1 behaves as a virtual component of the dynamic libraries, in that there is no detectable trace of its presence in the equilibrated mixtures, but becomes the major component-in the form of its copper(i) complex-when olefin cross-metathesis is carried out in the presence of a copper(i) salt. This journal is © the Partner Organisations 2014

Supramolecular loop stitches of discrete block molecules on graphite:tunable hydrophobicity by naphthalenediimide end-capped oligodimethylsiloxane

\u3cp\u3eThe noncovalent functionalization of surfaces has gained widespread interest in the scientific community, and it is progressively becoming an extremely productive research field offering brand new directions for both supramolecular and materials chemistry. As the end-groups often play a dominant role in the surface properties obtained, creating loops with end-groups only at the surface will lead to unexpected architectures and hence properties. Here we report the self-assembly of discrete block molecules - structures in-between block copolymers and liquid crystals - featuring oligodimethylsiloxanes (ODMS) end-capped with naphthalenediimides (NDIs) at the 1-phenyloctane/highly oriented pyrolytic graphite (1-PO/HOPG) interface. These structures produce unprecedented vertically nanophase-separated monolayers featuring NDI moieties that regularly arrange on the HOPG surface, while the highly dynamic ODMS segments form loops above them. Such arrangement is preserved upon drying and generates hydrophobic HOPG substrates in which the ODMS block length tunes the hydrophobicity. Thus, the exact structural fidelity of the discrete macromolecules allows for the correlation of nanoscopic organization with macroscopic properties of the self-assembled materials. We present a general strategy for tunable hydrophobic coatings on graphite based on molecularly combining crystalline aromatic moieties and immiscible oligodimethylsiloxanes.\u3c/p\u3

Variations in the fuel structure control the rate of the back and forth motions of a chemically fuelled molecular switch

\u3cp\u3eThis work deals with the use of 2-cyano-2-arylpropanoic acids as chemical fuels for an acid-base operated molecular switch that consists of a Sauvage-type catenand composed of two identical macrocycles incorporating a phenanthroline unit. When used as a base promoter of the decarboxylation of propanoic acid derivatives, the switch undergoes large amplitude motion from the neutral catenand to a protonated catenate and back again to the neutral state. The rate of back proton transfer, which determines the rate of the overall process, was markedly affected by para-substituents in the order Cl > H > CH\u3csub\u3e3\u3c/sub\u3e > OCH\u3csub\u3e3\u3c/sub\u3e (ρ = +5.2). Thus, the time required to complete a full cycle was almost two days for the OCH\u3csub\u3e3\u3c/sub\u3e derivative and dropped to a few minutes for the Cl derivative. These results show for the first time that the rate of operation of a molecular switch can be regulated by variations in the fuel structure.\u3c/p\u3