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Oligomers of benzoylalanine-based amidothioureas containing four β-turn structures spaced by meta-substituted benzenes were shown to undergo assembly in dilute CH3CN solution into supramolecular helices of enhanced supramolecular helicity, whereas those spaced by para-substituted benzene spacer(s) or those spaced by meta-substituted benzenes but with one or two β-turns exhibit a substantially decreased tendency of assembling. [ABSTRACT FROM AUTHOR]

We report that the core sequence of amyloid β (Aβ) peptide, KLVFF, when equipped with a C-terminal cysteine residue, exhibited an extremely low minimum hydrogelation concentration of 0.05 wt% in the presence of Ag+ in pH 5 buffer, with this concentration 2 orders of magnitude lower than that of the pentapeptide itself. The CD signal of the Ag+- L -KLVFFC hydrogel was observed to be sensitive to the early-stage aggregation of amyloid β peptide. [ABSTRACT FROM AUTHOR]

We investigated coordination polymers of Ag+ with a cysteine-based thiol ligand designed to contain a tetraphenylethylene AIEgen (L - and D -1). The coordination polymers, forming in a variety of protic and aprotic organic solvents, such as THF, CH3CN and CH3OH, were shown to undergo aggregation in H2O/THF binary solvents at water volume fractions above 50%, where emission was substantially enhanced while the CD profile was reversed, yet the dependence of the CD signal on ee remained S-shaped for the polymers in the aprotic organic solvents THF and CH3CN, in contrast to that in protic solvents CH3OH and C2H5OH. [ABSTRACT FROM AUTHOR]

Li2MnO3 is the parent compound of Li-rich Mn-based cathode materials for high energy density Li-ion batteries. The existence of oxygen vacancies yields anomalous capacity and can significantly increase the electrochemical activity of Li2MnO3, attracting considerable interest. However, the mechanism behind oxygen vacancies in Li2MnO3 is still under debate, due to the challenges in directly observing O and following relevant changes upon electrochemical cycling. Herein, to address the poor electrochemical activity of Li2MnO3 and further reveal its reaction mechanism, a mechanical thermal activation engineering strategy was used to synthesize Li2MnO3 with different contents of oxygen vacancies. The electronic structure can be effectively modulated by introducing different contents of oxygen vacancies in the local atomic coordination around Mn and O, which induces the distortion of the interfacial structure with a higher lattice d-spacing and effectively stimulates the electrochemical activity. By combining in situ XRD, ex situ XPS and ex situ Raman to investigate the evolution of Mn and O in Li2MnO3 during cycling. It is found that the Mn–O hybridization shows strong correlations with the oxygen redox behaviors, and high electrochemical activity and excellent cycling stability cannot coexist. Thus, the electrochemical activity and stability of Li2MnO3 are affected synchronously by lattice vacancies and local coordination configuration. This work provides valuable insights into the origin of electrochemical activity in Li2MnO3, which may inspire the design of high energy density cathode materials. [ABSTRACT FROM AUTHOR]

We propose to employ intramolecular chalcogen bonding to make a helical building block take its otherwise unfavorable cis-conformation. The 2,5-thiophenediamide motif was taken to bridge two β-turn structures to lead to an azapeptide that exists in cis-conformation and forms a halogen-bonded single-strand helix that exhibits a much stronger supramolecular helicity and a higher thermal stability. [ABSTRACT FROM AUTHOR]

Supramolecular helices from helical building blocks represent an emerging analogue of the α-helix. In cases where the helicity of the helical building block is well propagated, the head-to-tail intermolecular interactions that lead to the helix could be enhanced to promote the formation and the stability of the supramolecular helix, wherein homochiral elongation dominates and functional helical channel structures could also be generated. This feature article outlines the supramolecular helices built from helical building blocks, i.e., helical aromatic foldamers and helical short peptides that are held together by intermolecular π–π stacking, hydrogen/halogen/chalcogen bonding, metal coordination, dynamic covalent bonding and solvophobic interactions, with emphasis on the influence of efficient propagation of helicity during assembly, favouring homochirality and channel functions. [ABSTRACT FROM AUTHOR]

We report a supramolecular nanosphere with a diameter of 8.65 nm built in an aqueous solution via dynamic binding of glucose to a thiol ligand bearing a phenylboronic acid group, 4-mercaptophenylboronic acid (4-MPBA), as a hydrophilic component in combination with a hydrophobic thiol ligand, 1-octanethiol (n-C8H17SH), in the presence of Ag+. Highly hydrophilic glucose binding to two neighboring boronic acid groups from 4-MPBA ligands on their Ag+ coordination polymeric backbone, on which the hydrophobic n-C8H17SH ligands locate inwards, drives the coordination polymers into nanospheres. The supramolecular nanospheres are of small diameters with narrow size distribution characteristic of glucose among the tested monosaccharides including fructose and xylose. [ABSTRACT FROM AUTHOR]

We propose to create nanospheres in aqueous solutions from coordination polymers of Ag+ with a combination of a hydrophilic and a hydrophobic thiol, of diameter ca. 2.7 nm in the case of using cysteine and n-butanethiol. A spectral probe for the formation of the nanospheres is a reversal of the CD signal at 253 nm from negative in the case of cysteine alone to positive when cysteine and n-BuSH are both employed, together with an amplification. [ABSTRACT FROM AUTHOR]

We report supramolecular helical assembly in water of β-turn structured bis(N-amidothioureas) containing Br-substitutes of moderate halogen bonding ability, promoted by stronger hydrophobic interaction. The helical polymers show an unusual negative nonlinear CD-ee dependence. [ABSTRACT FROM AUTHOR]

We propose using the formation of coordination polymers of Ag+ to probe differences between the perfluorinated alkyl chain and the alkyl chain by deriving a thiol ligand, N-(perfluoroalkanoyl)cysteine. Rapid formation in EtOH of P-/M-helical nanofibrils of high thermostability was found for N-(perfluorooctanoyl)- L -/ D -cysteine ethyl esters at the μM level upon mixing with Ag+, but not for the octanoyl counterpart. This difference was also observed in terms of circular dichroism-enantiomeric excess dependence. [ABSTRACT FROM AUTHOR]

This study demonstrates a robust and ultra-stable sodium infiltrated Fe2O3 coated carbon textile (SFCT) anode with excellent machinability. The obtained SFCT anode overcomes the disadvantage of Na electrodes, which is not easily processable, and exhibits more flat voltage profiles, lower stripping/plating overpotential, and better cycling stability in an additive-free carbonate-based electrolyte compared with bare Na electrodes. [ABSTRACT FROM AUTHOR]

Traditionally, fluorescence probes have focused on the detection of a single biomarker for a specific process. In this work, we set out to develop a number of fluorescence probes that enable the detection of a chosen analyte in the presence of reactive oxygen/nitrogen species (ROS/RNS). These fluorescence probes when activated result in the formation of the highly fluorescent pink dye, resorufin. Therefore, we have labelled these fluorescent probes as ‘Pinkments’. Our first ‘Pinkment’ was shown to detect biologically relevant concentrations of ONOO− and have an excellent selectivity against other ROS/RNS. Pinkment-OH was developed to provide a core unit which could be easily functionalised to produce a range of ‘AND’ based fluorescence probes for the detection of ROS/RNS and a second analyte. For proof of concept, we synthesised Pinkment-OTBS and Pinkment-OAc. These ‘AND’-based probes were successfully shown to detect ROS/RNS and F− or esterase, respectively. [ABSTRACT FROM AUTHOR]

Herein, we report a conformation switching-based fluorescence sensing scheme using dipeptide-based amidothioureas (azapeptides) that contain a folded β-turn structure. Amidothiourea is equipped at its two termini with an electron acceptor and an electron donor or two fluorophores, such that it exhibits enhanced exciplex or excimer emission because of the turn structure in which the two termini are brought into close proximity; on the other hand, it exhibits a dramatic ratiometric fluorescence response upon anion binding to the thiourea moiety because of the resultant extended conformation of the anion binding complex. [ABSTRACT FROM AUTHOR]

The glassy transition of superparamagnetic (SPM) (r ＜ r0) nanoparticle systems usually occurs at a very low temperature that greatly limits its application to high temperatures. In this work, we report a spin-glass-like (SGL) behavior near the Curie point (TC), i.e., T0 = 330 K, in La0.67Sr0.33MnO3 (LSMO) nanofibers (NFs) composed of nanoparticles beyond the SPM size (r>r0), resulting in a significant increase of the glass transition temperature. This SGL transition near the TC of bulk LSMO can be explained to be the scenario of locally ordered clusters embedded in a disordered host, in which the assembly of nanoparticles has a magnetic core–shell model driven by surface spin glass. The presence of a surface spin glass of nanoparticles was proved by the Almeida–Thouless line δTf∝H2/3, exchange bias, and reduced saturation magnetization of the NF system. Composite dynamics were found – that is, both the SPM and the super-spin-glass (SSG) behavior are found in such an NF system. The bifurcation of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization vs. temperature curves at the ZFC peak, and the flatness of FC magnetization involve SSG, while the frequency-dependent ac susceptibility anomaly follows the Vogel–Fulcher law that implies weak dipole interactions of the SPM model. This finding can help us to find a way to search for high temperature spin glass materials. [ABSTRACT FROM AUTHOR]

Reversible covalent binding of boronic acids with polyols and Lewis bases has facilitated the development of robust chemosensors for many biologically important species under physiologically or environmentally relevant conditions. This minireview covers selected examples of advances reported in this area from 2014 to 2016. While the discovery of new boron-containing binding motifs and identification of new analytical targets have expanded the ultility of boronic acid-based molecular recognition, unconventional sensing strategies such as exploitation of nanoscale self-assembly, multicomponent dynamic covalent assembly, and coupling boronate ester formation with a further chemical reaction have led to significantly improved sensor performance, enabling real-world applications in various areas such as cell biology and asymmetric catalysis. [ABSTRACT FROM AUTHOR]

We report that in the Ag+ coordination polymers of a chiral thiol ligand containing an AIE fluorophore, tetraphenylethene (TPE), the TPE chromophores experience H-type aggregation, and yet a substantial enhancement of the fluorescence is observed, though to a lesser extent than that in the aggregates of the thiol ligand itself, which undergoes J-type aggregation. We show that this is not due to the difference in the freedom of the rotation of the fluorophore in the two types of aggregate, but is due to a small increase in the radiation rate constant in the coordination polymers while the much higher radiationless rate constant remains more or less unchanged. [ABSTRACT FROM AUTHOR]

As a new emerging area in chemical sensing, sensing using supramolecular aggregates exhibits unique advantages over that using conventional small-molecule chemical sensors, in terms of high sensitivity and selectivity, and the simplicity of the sensory building blocks. This Feature Article outlines the recent research progress made in sensing based on induced supramolecular aggregation–disaggregation. The reviewed sensory building blocks, in general, in the form of a small molecular sensor, yet with a much simpler structure, which form aggregates, are those of perylene derivatives, pyrene derivatives, tetraphenylethylene derivatives, metallophilic species and metal–organic frameworks. [ABSTRACT FROM AUTHOR]

Glucose binding via boronate ester linkages selectively triggers imine bond formation between 4-formylphenylboronic acid and octylamine, leading to the formation of vesicular aggregates in aqueous solutions. This “double dynamic covalent assembly” allows the facile selective sensing of glucose against the otherwise serious interferant fructose, without the need to resort to synthetic effort. [ABSTRACT FROM AUTHOR]

A near infrared probe for sensitive colorimetric and fluorimetric detection of nerve agent mimics, DCP and DCNP, was reported based on the activation of a carboxylic acid group by the mimics to conduct an intramolecular amidation reaction in the heptamethine chromophore, where its absorption or excitation maximum wavelength could be greatly red-shifted by attenuating the electron-donating ability of the amine group in the bridgehead site of heptamethine cyanine. [ABSTRACT FROM AUTHOR]

A mixture of two simple perylene-containing receptors was found to bind bifunctional l-DOPA synergistically and tightly via orthogonal boronate ester and imine bond formation in neutral aqueous solutions, the resulting three-component assembly forming optically active long fibrous aggregates. [ABSTRACT FROM AUTHOR]

Optical sensors that respond to enantiomeric excess of chiral analytes are highly demanded in chirality related research fields and demonstrate their potential in many applications, for example, screening of asymmetric reaction products. Most sensors developed so far are small molecules. This Tutorial Review covers recent advances in chirality sensing systems that are different from the traditional small molecule-based sensors, by using macrocycles, synthetic oligomers/polymers, supramolecular polymers and nanoparticles as the sensors, in which supramolecular interactions operate. [ABSTRACT FROM AUTHOR]

A supramolecular polymeric system that shows an unusual “racemate-rules” chiroptical property, an effect opposite to the well-known “majority-rules”, has been utilized for accurate determination of malic acid enantiopurity at high ee values. [ABSTRACT FROM AUTHOR]

The reversible boronic acid–diol interaction empowers boronic acid receptors' saccharide binding capacities, rendering them a class of lectin mimetic, termed “boronlectins”. Boronic acids follow lectin functions not just in being able to bind saccharides, but in multivalent saccharide binding that enhances both affinity and selectivity. For almost a decade, efforts have been made to achieve and improve selectivity for given saccharide targets, most notably glucose, by using properly positioned boronic acids, offering multivalent interactions. Incorporation of several boronic acid groups into a covalent framework or non-covalent assembly of boronic acid are two general methods used to create such smart sensors, of which the latter resembles lectin oligomerisation that affords multivalent saccharide-binding architectures. In this review, we discuss supramolecular selective sensing of saccharides by using simple boronic acids in their aggregate forms, after a brief survey of the general aspects of boronic acid-based saccharide sensing. [ABSTRACT FROM AUTHOR]

This critical reviewhighlights recent advances in the structurally modified (thio)urea-based receptors for anion complexation and sensing. Modifications of the (thio)urea structure are aimed at a better anion binding in terms of higher binding constant, anion selectivity and feasibility. Major (thio)urea receptors are reviewed as N-alkyl, N-aryl and N-amido/N-amino (thio)ureas. Hints for designing (thio)urea-based receptors for anions are discussed (102 references). [ABSTRACT FROM AUTHOR]

We report a novel example of ligand-chirality finely controlled in situsupramolecular hydrogel formation based on the coordination of phenylalanine (Phe) to Cu(ii) with higher selectivity over other metal ions. As decreasing both enantiomeric excesses (ee%) of ligand Phe towards its d- and l-forms, the gelation ability of Phe-Cu(ii) supramolecular metallogelator was found to be weakened and eventually disappeared, which likely resulted from the stereoselectivity of the ligand Phe. Intermolecular hydrogen bonding, hydrophobic and/or π–π stacking interactions were also found to be essential for forming the metallogel. We believe that the present work can open up a new entry for developing novel and promising chiral sensing and recognition platforms, i.e.visually sensing chiral molecules by naked eyes due to the feature of a sol-to-gel transition induced smartly by varying the ligand chirality. [ABSTRACT FROM AUTHOR]

We report here chirality sensing using achiral Ag+–thiol coordination polymers as the framework which becomes CD active upon interaction with chiral species, taking p-mercaptophenylboronic acid as a thiol ligand that bears a binding group for monosaccharides. [ABSTRACT FROM AUTHOR]

Transforming the C-terminal amide of a glycinylphenylalanine dipeptide into N-amidothiourea affords a β-turn structure in the formed dipeptide based N-amidothioureas, which can be readily identified by an induced CD signal from the achiral phenylthiourea chromophore. [ABSTRACT FROM AUTHOR]

An operationally simple colorimetric method for enantioselective detection of chiral secondary alcohols via hydrogen bonding interactions using a chiral ferrocene derivative is reported. [ABSTRACT FROM AUTHOR]

We have developed a simple and robust fluorescence based boronic-acid molecular sensor for determining the concentration of fluoride in water at environmentally significant levels. The simplicity of the method and the ability to measure fluoride in water between 0.1 and 1.5 ppm is particularly noteworthy given the WHO requirements for detecting levels of fluoride in drinking water below 1.5 ppm. [ABSTRACT FROM AUTHOR]

N-Amidothioureas generated from amine-dimethylated natural l-phenylalanine and its d-enantiomer bearing a chiral carbon that is by 2 atoms or 3 chemical bonds away from the anion binding site establish chiral communication upon acetate anion binding to the thiourea moiety. [ABSTRACT FROM AUTHOR]

Developing of alternative chiral thiol stabilizers from the assembly of achiral thiol (e.g.thioglycolic acid) and chiral ligand (e.g.arginine) viaboth hydrogen bonding and electrostatic interactions was proposed and successfully applied to an efficient preparation of chiral CdS quantum dots (QDs). Chiral CdS QDs capped mainly with achiral thioglycolic acid were also obtained that may allow the chiral QDs to be modified for extended applications. [ABSTRACT FROM AUTHOR]

The exciplex formation between a pyridinium boronic acid and phenyl group connected viaa propylene linker can be monitored using fluorescence. Addition of pinacol affords a cyclic boronate ester with enhanced Lewis acidity that increases the strength of its cation–π stacking interaction causing a four-fold fluorescence enhancement. [ABSTRACT FROM AUTHOR]

The exciplex formation between a pyridinium boronic acid and phenyl group connected viaa propylene linker can be monitored using fluorescence. Addition of pinacol affords a cyclic boronate ester with enhanced Lewis acidity that increases the strength of its cation–π stacking interaction causing a four-fold fluorescence enhancement. [ABSTRACT FROM AUTHOR]

We found that melamine in its protonated form could be triggered by oxoanions such as NO3−, PO43−, ATP, and SO42−to form superstructures and to gelate a large amount of water molecules, presumably resulting from the electrostatic and hydrogen bonding interactions operating in a synergistic manner; the gelation can be reversibly switched off/on by increasing/decreasing pH or temperature. [ABSTRACT FROM AUTHOR]

Substantially enhanced monosaccharide fluorescent sensing in aqueous solutions using a simple phenylboronic acid receptor is achieved by coupling the classic strategy based on saccharide–boronic acid interaction with catalytic Suzuki homocoupling reaction. [ABSTRACT FROM AUTHOR]

Hg2+was found to specifically induce the aggregation of perylene bisimide in a “thymine–Hg2+–thymine” binding motif and the resultant aggregates showed a highly selective and sensitive turn-on fluorescence response for cysteine, with a detection limit down to 9.6 nM. [ABSTRACT FROM AUTHOR]

We propose using the formation of coordination polymers of Ag+ to probe differences between the perfluorinated alkyl chain and the alkyl chain by deriving a thiol ligand, N-(perfluoroalkanoyl)cysteine. Rapid formation in EtOH of P-/M-helical nanofibrils of high thermostability was found for N-(perfluorooctanoyl)- L -/ D -cysteine ethyl esters at the μM level upon mixing with Ag+, but not for the octanoyl counterpart. This difference was also observed in terms of circular dichroism-enantiomeric excess dependence. [ABSTRACT FROM AUTHOR]

We report that the core sequence of amyloid β (Aβ) peptide, KLVFF, when equipped with a C-terminal cysteine residue, exhibited an extremely low minimum hydrogelation concentration of 0.05 wt% in the presence of Ag + in pH 5 buffer, with this concentration 2 orders of magnitude lower than that of the pentapeptide itself. The CD signal of the Ag + -L-KLVFFC hydrogel was observed to be sensitive to the early-stage aggregation of amyloid β peptide.

We investigated coordination polymers of Ag + with a cysteine-based thiol ligand designed to contain a tetraphenylethylene AIEgen (L- and D-1). The coordination polymers, forming in a variety of protic and aprotic organic solvents, such as THF, CH 3 CN and CH 3 OH, were shown to undergo aggregation in H 2 O/THF binary solvents at water volume fractions above 50%, where emission was substantially enhanced while the CD profile was reversed, yet the dependence of the CD signal on ee remained S-shaped for the polymers in the aprotic organic solvents THF and CH 3 CN, in contrast to that in protic solvents CH 3 OH and C 2 H 5 OH.