A self-assembled supramolecular optical sensor for NiII, CdII, and CrIII

A new chromogenic supramolecular sensor for transition metals is reported. It is based on a newly designed phenanthroline-containing molecule that self-assembles via an organometallic "clip" into a supramolecular optical sensor for metals. [reaction: see text]     

Strong,Self-Healable,and Recyclable Visible-Light-Responsive Hydrogel Actuators

The most pressing challenges for light-driven hydrogel actuators include reliance on UV light, slow response, poor mechanical properties, and limited functionalities. Now, a supramolecular design strategy is used to address these issues. Key is the use of a benzylimine-functionalized anthracene group, which red-shifts the absorption into the visible region and also stabilizes the supramolecular network through π–π interactions. Acid–ether hydrogen bonds are incorporated for energy dissipation under mechanical deformation and maintaining hydrophilicity of the network. This double-crosslinked supramolecular hydrogel developed via a simple synthesis exhibits a unique combination of high strength, rapid self-healing, and fast visible-light-driven shape morphing both in the wet and dry state. As all of the interactions are dynamic, the design enables the structures to be recycled and reprogrammed into different 3D objects.     

Hierarchical self-assembly,coassembly, and self-organization of novel liquid crystalline lattices and superlattices from a twin-tapered dendritic benzamide and its four-cylinder-bundle supramolecular polymer

The synthesis and structural analysis of the twin-dendritic benzamide 10, based on the first-generation, self-assembling, tapered dendrons 3,4,5-tris(4'-dodecyloxybenzyloxy)benzoic acid and 3,4,5-tris(4'-dodecyloxybenzyloxy)-1-aminobenzene, and the polymethacrylate, 20, which contains 10 as side groups, are presented. Benzamide 10 self-assembles into a supramolecular cylindrical dendrimer that self-organizes into a columnar hexagonal (Phi(h)) liquid crystalline (LC) phase. Polymer 20 self-assembles into an imperfect four-cylinder-bundle supramolecular dendrimer, and creates a giant vesicular supercylinder that self-organizes into a columnar nematic (N(c)) LC phase which displays short-range hexagonal order. In mixtures of 20 and 10, 10 acts as a guest and 20 as a host to create a perfect four-cylinder-bundle host-guest supramolecular dendrimer that coorganizes with 10. A diversity of Phi(h), simple rectangular columnar (Phi(r-s)) and centered rectangular columnar (Phi(r-c)), superlattices are produced at different ratios between 20 and 10. This diversity of LC lattices and superlattices is facilitated by the architecture of the twin-dendritic building block, polymethacrylate, the host-guest supramolecular assembly, and by hydrogen bonding along the center of the supramolecular cylinders generated from 10 and 20.     

Metallogels from Coordination Complexes,Organometallic, and Coordination Polymers

A supramolecular gel results from the immobilization of solvent molecules on a 3D network of gelator molecules stabilized by various supramolecular interactions that include hydrogen bonding, π–π stacking, van der Waals interactions, and halogen bonding. In a metallogel, a metal is a part of the gel network as a coordinated metal ion (in a discrete coordination complex), as a cross‐linking metal node with a multitopic ligand (in coordination polymer), and as metal nanoparticles adhered to the gel network. Although the field is relatively new, research into metallogels has experienced a considerable upsurge owing to its fundamental importance in supramolecular chemistry and various potential applications. This focus review aims to provide an insight into the development of designing metallogelators. Because of the limited scope, discussions are confined to examples pertaining to metallogelators derived from discrete coordination complexes, organometallic gelators, and coordination polymers. This review is expected to enlighten readers on the current development of designing metallogelators of the abovementioned class of molecules.     

Strong,Self‐Healable,and Recyclable Visible‐Light‐Responsive Hydrogel Actuators

The most pressing challenges for light‐driven hydrogel actuators include reliance on UV light, slow response, poor mechanical properties, and limited functionalities. Now, a supramolecular design strategy is used to address these issues. Key is the use of a benzylimine‐functionalized anthracene group, which red‐shifts the absorption into the visible region and also stabilizes the supramolecular network through π–π interactions. Acid–ether hydrogen bonds are incorporated for energy dissipation under mechanical deformation and maintaining hydrophilicity of the network. This double‐crosslinked supramolecular hydrogel developed via a simple synthesis exhibits a unique combination of high strength, rapid self‐healing, and fast visible‐light‐driven shape morphing both in the wet and dry state. As all of the interactions are dynamic, the design enables the structures to be recycled and reprogrammed into different 3D objects.     

Supramolecular polymerization of oligopyrenotides--control by single, natural nucleotides

Amphiphilic heptapyrenotides (Py(7)) assemble into supramolecular polymers. Here we present a comprehensive spectroscopic study of aggregates and co-aggregates of the non-chiral Py(7) and its mono- or di-substituted nucleotide analogs (Py(7)-N and N-Py(7)-N'). The data show that the formation of supramolecular polymers from oligopyrenotides is highly sensitive to the nature of the attached, chiral auxiliary. A single natural nucleotide may be sufficient for the fine tuning of the aggregates' properties by changing the mechanism of aggregation from an isodesmic to a nucleation-elongation process, which results in a high degree of amplification of chirality in the formed supramolecular polymers. Watson-Crick complementarity does not play a significant role, since co-aggregates of oligomers modified with complementary nucleotides show no signs of supramolecular polymerization. Depending on the nucleotide, the helical sense of the polymers is shifted to an M-helix or a P-helix. The findings demonstrate the value of oligopyrenotides as oligomeric building blocks for the generation of optically active supramolecular polymers.     

Solvent‐Polarity‐Tuned Morphology and Inversion of Supramolecular Chirality in a Self‐Assembled Pyridylpyrazole‐Linked Glutamide Derivative: Nanofibers,Nanotwists, Nanotubes,and Microtubes

The self‐assembly of a low‐molecular‐weight organogelator into various hierarchical structures has been achieved for a pyridylpyrazole linked L ‐glutamide amphiphile in different solvents. Upon gel formation, supramolecular chirality was observed, which exhibited an obvious dependence on the polarity of the solvent. Positive supramolecular chirality was obtained in nonpolar solvents, whereas it was inverted into negative supramolecular chirality in polar solvents. Moreover, the gelator molecules self‐assembled into a diverse array of nanostructures over a wide scale range, from nanofibers to nanotubes and microtubes, depending on the solvent polarity. Such morphological changes could even occur for the xerogels in the solvent vapors. We found that the interactions between the pyridylpyrazole headgroups and the solvents could subtly change the stacking of the molecules and, hence, their self‐assembled nanostructures. This work exemplifies that organic solvents can significantly involve the gelation, as well as tune the structure and properties, of a gel.     

Functional, hierarchically structured poly(diacetylene)s via supramolecular self-assembly

The supramolecular self-assembly of macromonomers may serve as a first step to prepare well-defined, highly functionalized, hierarchically structured, conjugated polymers. Functional diacetylene macromonomers equipped with an oligopeptide segment designed to promote self-assembly into parallel beta-sheet type structures and a polydisperse, aliphatic coil segment to prevent global ordering give rise to supramolecular polymers with a tubular double-helical quarternary structure in organic solution. These supramolecular polymers may then be converted into the corresponding poly(diacetylene)s by UV irradiation under retention of their hierarchical structure.     

Multicomponent Crystal of Metformin and Barbital: Design,Crystal Structure Analysis and Characterization

The formation of most multicomponent crystals relies on the interaction of hydrogen bonds between the components, so rational crystal design based on the expected hydrogen-bonded supramolecular synthons was employed to establish supramolecular compounds with desirable properties. This theory was put into practice for metformin to participate in more therapeutic fields to search for a fast and simple approach for the screening of candidate crystal co-formers. The prediction of intermolecular synthons facilitated the successful synthesis of a new multicomponent crystal of metformin (Met) and barbital (Bar) through an anion exchange reaction and cooling crystallization method. The single crystal X-ray diffraction analysis demonstrated the hydrogen bond-based ureide/ureide and guanidine/ureide synthons were responsible for the self-assembly of the primary structural motif and extended into infinite supramolecular heterocatemeric structures.     

Facile Synthesis of Supramolecular Ionic Polymers That Combine Unique Rheological,Ionic Conductivity,and Self‐Healing Properties

A new family of supramolecular ionic polymers is synthesized by a simple method using (di‐/tri‐)carboxylic acids and (di‐/tri‐)alkyl amines. These polymers are formed by carboxylate and ammonium molecules that are weakly bonded together by a combination of ionic and hydrogen bonds, becoming solid at room temperature. The supramolecular ionic polymers show a sharp rheological transition from a viscoelastic gel to a viscous liquid between 30 and 80 °C. This sharp viscosity decrease is responsible for an unprecedented jump in ionic conductivity of four orders of magnitude in that temperature range. As a potential application, this chemistry can be used to develop polymeric materials with self‐healing properties, since it combines properties from supramolecular polymers and ionomers into the same material.     

Self-organization of a self-assembled supramolecular rectangle, square, and three-dimensional cage on Au111 surfaces

The structure and conformation of three self-assembled supramolecular species, a rectangle, a square, and a three-dimensional cage, on Au111 surfaces were investigated by scanning tunneling microscopy. These supramolecular assemblies adsorb on Au111 surfaces and self-organize to form highly ordered adlayers with distinct conformations that are consistent with their chemical structures. The faces of the supramolecular rectangle and square lie flat on the surface, preserving their rectangle and square conformations, respectively. The three-dimensional cage also forms well-ordered adlayers on the gold surface, forming regular molecular rows of assemblies. When the rectangle and cage were mixed together, the assemblies separated into individual domains, and no mixed adlayers were observed. These results provide direct evidence of the noncrystalline solid-state structures of these assemblies and information about how they self-organize on Au111 surfaces, which is of importance in the potential manufacturing of functional nanostructures and devices.     

Synthesis, structure and photophysical properties of two transitional metal supramolecular complexes

Two supramolecular complexes: [Co(2,6-PDC)(Hdmpz)3]·H2O (1) and [Zn(2,6-PDC)(Hdmpz)2] (2) {2,6-PDC=pyridine-2,6-dicarboxylic acid, Hdmpz=3,5-dimethylpyrazol}, self-assembles via O-H?O and N-H?O hydrogen bondings into supramolecular networks, which are characterized by elemental analyses, IR spectra and single crystal X-ray diffraction analysis. Both of them consist of two-dimensional networks that are stacked together by typical hydrogen bonding interactions (i.e. O-H?O and N-H?O), which often play important roles in the formation of low-dimensional into high-dimensional supramolecular networks. In addition, quantum chemistry calculations and surface photovoltage spectroscopy are performed firstly with the complexes.     

Thermodynamics of supramolecular naphthalenediimide nanotube formation: the influence of solvents, side chains, and guest templates

Amino-acid functionalized naphthalenediimides self-assemble into hydrogen-bonded supramolecular helical nanotubes via a noncooperative, isodesmic process; the self-assembly of ordered helical systems is usually realized through a cooperative process. This unexpected behavior was rationalized as a manifestation of entropy-enthalpy compensation. Fundamental insights into the thermodynamics governing this self-assembly were obtained through the fitting of the isodesmic model to (1)H NMR spectrometry and circular dichroism spectroscopy measurements. Furthermore, we have extended the application of this mathematical model, for the first time, to quantitatively estimate the effect of guests, solvents, and side chains on the stability of the supramolecular nanotube; most significantly, we demonstrate that C(60) acts as a template to stabilize the nanotube assembly and thereby substantially increase the degree of polymerization.     

Urea Derivatives as Functional Molecules: Supramolecular Capsules,Supramolecular Polymers,Supramolecular Gels,Artificial Hosts,and Catalysts

Urea, which has both hydrogen bond acceptor and donor moieties, is an ideal structure for a supramolecular synthon. Various supramolecules having ureido group(s) have been widely developed. This article summarizes recent developments of urea derivatives that exhibit various functions: i) supramolecular capsules that form discrete urea–urea intermolecular hydrogen bonds, ii) supramolecular polymers that form continuous urea–urea intermolecular hydrogen bonds, iii) supramolecular gels that form continuous urea–urea intermolecular hydrogen bonds, iv) artificial host molecules based on the molecular recognition ability of the ureido group, and v) catalytic reactions developed by utilizing the molecular recognition ability of the ureido group.     

[5]Rotaxane,linear polymer and supramolecular organic framework constructed by nor-seco-cucurbit[10]uril-based ternary complexation

Here we use nor-seco-cucurbit[10]uril (ns-CB[10]) based ternary complexation to construct [5]rotaxane, linear supramolecular dynamic rotaxane polymers and cubic 3D supramolecular organic framework. A [5]rotaxane is constructed by ns-CB[10], TMeCB[6] and short linear derivatives of 4,4′-bipyridinium (M2). ns-CB[10], CB[7] and long linear derivatives of 4,4′-bipyridinium (M3) self-assemble into a linear supramolecular dynamic rotaxane polymer. ns-CB[10] and tetracationic tetrahedral monomer self-assemble and form a three-dimensional supramolecular organic framework. The above results demonstrate that ns-CB[10]-based ternary complexation is a versatile platform to build various supramolecular systems.     

Mixed Conductive,Injectable, and Fluorescent Supramolecular Eutectogel Composites

Eutectogels are an emerging family of soft ionic materials alternative to ionic liquid gels and organogels, offering fresh perspectives for designing functional dynamic platforms in water-free environments. Herein, the first example of mixed ionic and electronic conducting supramolecular eutectogel composites is reported. A fluorescent glutamic acid-derived low-molecular-weight gelator (LMWG) was found to self-assemble into nanofibrillar networks in deep eutectic solvents (DES)/poly(3,4-ethylenedioxythiophene) (PEDOT): chondroitin sulfate dispersions. These dynamic materials displayed excellent injectability and self-healing properties, high ionic conductivity (up to 10⁻² S cm⁻¹), good biocompatibility, and fluorescence imaging ability. This set of features turns the mixed conducting supramolecular eutectogels into promising adaptive materials for bioimaging and electrostimulation applications.     

Synthesis, self-assembly, and characterization of supramolecular polymers from electroactive dendron rodcoil molecules

We report here the synthesis and self-assembly of a series of three molecules with dendron rodcoil architecture that contain conjugated segments of oligo(thiophene), oligo(phenylene-vinylene), and oligo(phenylene). Despite their structural differences, all three molecules yield similar self-assembled structures. Electron and atomic force microscopy reveals the self-assembly of the molecules into high aspect ratio ribbon-like nanostructures which at low concentrations induce gelation in nonpolar solvent. Self-assembly results in a blue-shifted absorption spectrum and a red-shifted, quenched fluorescence spectrum, indicating aggregation of the conjugated segments within the ribbon-like structures. The assembly of these molecules into one-dimensional nanostructures is a route to pi-pi stacked supramolecular polymers for organic electronic functions. In the oligo(thiophene) derivative, self-assembly leads to a 3 orders of magnitude increase in the conductivity of iodine-doped films due to self-assembly. We also found that electric field alignment of these supramolecular assemblies can be used to create arrays of self-assembled nanowires on a device substrate.     

Self‐Healing,Expansion–Contraction,and Shape‐Memory Properties of a Preorganized Supramolecular Hydrogel through Host–Guest Interactions

Supramolecular materials cross‐linked between polymer chains by noncovalent bonds have the potential to provide dynamic functions that are not produced by covalently cross‐linked polymeric materials. We focused on the formation of supramolecular polymeric materials through host–guest interactions: a powerful method for the creation of nonconventional materials. We employed two different kinds of host–guest inclusion complexes of β‐cyclodextrin (βCD) with adamantane (Ad) and ferrocene (Fc) to bind polymers together to form a supramolecular hydrogel (βCD‐Ad‐Fc gel). The βCD‐Ad‐Fc gel showed self‐healing ability when damaged and responded to redox stimuli by expansion or contraction. Moreover, the βCD‐Ad‐Fc gel showed a redox‐responsive shape‐morphing effect. We thus succeeded in deriving three functions from the introduction of two kinds of functional units into a supramolecular material.     

Novel potentially antibacterial naphthalimide-derived metronidazoles: Design,synthesis, biological evaluation and supramolecular interactions with DNA,human serum albumin and topoisomerase Ⅱ

A series of novel naphthalimide-derived metronidazoles as new type of antimicrobial agents were for the first time designed, synthesized and characterized by NMR, IR and HRMS spectra. Experimental results revealed that most of them displayed moderate to good antibacterial activity towards Gram-positive and negative bacteria. Especially, compound 7b was able to not only exhibit effective inhibition towards the growth of P. vulgaris (MIC=0.002 μmol/mL) and S. dysenteriae (MIC=0.01 μmol/mL), but also have rapidly killing effect and prevent the development of bacterial resistance. Further research revealed that the highly active molecule 7b could not only intercalate into calf thymus DNA to form a steady supramolecular complex and thus might block DNA replication to exert the powerful bioactivities, but also be effectively transported by human serum albumin (HSA) via the formation of the 1:1 supramolecular complex, in which hydrogen bonds and hydrophobic effect played important roles in the association of compound 7b with HSA. Molecular docking indicated that the supramolecular interactions between 7b and topoisomerase Ⅱ were driven by hydrogen bonds.     

Self‐Healing,Expansion–Contraction,and Shape‐Memory Properties of a Preorganized Supramolecular Hydrogel through Host–Guest Interactions

Supramolecular materials cross‐linked between polymer chains by noncovalent bonds have the potential to provide dynamic functions that are not produced by covalently cross‐linked polymeric materials. We focused on the formation of supramolecular polymeric materials through host–guest interactions: a powerful method for the creation of nonconventional materials. We employed two different kinds of host–guest inclusion complexes of β‐cyclodextrin (βCD) with adamantane (Ad) and ferrocene (Fc) to bind polymers together to form a supramolecular hydrogel (βCD‐Ad‐Fc gel). The βCD‐Ad‐Fc gel showed self‐healing ability when damaged and responded to redox stimuli by expansion or contraction. Moreover, the βCD‐Ad‐Fc gel showed a redox‐responsive shape‐morphing effect. We thus succeeded in deriving three functions from the introduction of two kinds of functional units into a supramolecular material.