Supramolecular Chemistry in Water

A protocol for hydrogenation of aldehydes and ketones to alcohols in aqueous media at room temperature in high yields and purity

In this paper, the hydrogenation of aldehydes and ketones using the RANEY® nickel catalyst was successfully applied for the synthesis of alcohol compounds without additional column chromatographic purification. This synthetic strategy features a wide range of substrates, excellent atom economy, high chemical discrimination and the use of a ligand-free catalytic system. Reactions were performed at room temperature in water providing alcohols in high yields and purity.

Umbrella-Shaped Amphiphiles: Internal Alkylation of an Aromatic Micelle and Its Impact on Cavity Features

To develop new hybrid micelles with alkyl/polyaromatic core-shell structures, we synthesized umbrella-shaped amphiphiles bearing a bent anthracene dimer with a linear alkyl chain (i.e., octyl and hexadecyl groups). The amphiphiles quantitatively assemble into spherical micelles (~2-3 nm in core diameter), possessing an alkylated cavity surrounded by a polyaromatic framework, in water. The alkylation significantly enhances the stability of the micellar structures against dilution (up to 9 μM) and heat (up to >120 °C). The highly condensed hexadecyl core of the hybrid micelle, as indicated by solvatochromic guest probes, displays increased uptake ability toward large alkylated metallodyes. Interestingly, efficient uptake of aromatic macrocycles (i.e., [n]cycloparaphenylenes) by the present micelle provides pseudorotaxane-shaped host-guest composites with high emissivity (ΦF=up to 35 %). Internal multi-alkylation of an aromatic micelle can thus successfully enhance its assembly stability/guest uptake functions.

Biomimetic Hydrogen-Bonded G ⋅ C ⋅ G ⋅ C Quadruplex within a Tetraphenylethene-Based Octacationic Spirobicycle in Water

In biological systems, nucleotide quadruplexes (such as G-quadruplexes) in DNA and RNA that are held together by multiple hydrogen bonds play a crucial functional role. The biomimetic formation of these hydrogen-bonded quadruplexes captured by artificial systems in water poses a significant challenge but can offer valuable insights into these complex functional structures. Herein, we report the formation of biomimetic hydrogen-bonded G ⋅ C ⋅ G ⋅ C quadruplex captured by a tetraphenylethene (TPE) based octacationic spirobicycle (1). The spirobicyclic compound possesses a three-dimensional (3D) crossing dual-cavity structure, which enables the encapsulation of four d(GpC) dinucleotide molecules, thereby realizing 1 : 4 host-guest complexation in water. The X-ray structure reveals that four d(GpC) molecules further form a two-layer G ⋅ C ⋅ G ⋅ C quadruplex with Watson-Crick hydrogen bonds, which are stabilized within the dual hydrophobic cavities of 1 through the cooperative non-covalent interactions of hydrogen bonds, CH⋅⋅⋅π interactions, and hydrophobic effect. Due to the dynamically-rotational propeller chirality of TPE units, 1 with adaptive chirality can further serve as a chiroptical sensor to exhibit opposite Cotton effects with mirror-image CD spectra for the pH-dependent hydrogen-bonded assemblies of d(GpC) including the Watson-Crick G ⋅ C ⋅ G ⋅ C (pH 9.22) and Hoogsteen G ⋅ C+ ⋅ G ⋅ C+ (pH 5.74) quartets through the host-guest chirality transfer in water.

Discovery of selective monosaccharide receptors via dynamic combinatorial chemistry

The molecular recognition of saccharides by synthetic hosts has become an appealing but elusive task in the last decades. Herein, we combine Dynamic Combinatorial Chemistry (DCC) for the rapid self-assembly and screening of virtual libraries of receptors, with the use of ITC and NMR to validate the hits and molecular modelling to understand the binding mechanisms. We discovered a minimalistic receptor, 1F (N-benzyl-L-phenylalanine), with considerable affinity for fructose (Ka = 1762 M-1) and remarkable selectivity (>50-fold) over other common monosaccharides. The approach accelerates the discovery process of receptors for saccharides.

Probing Ion-Receptor Interactions in Halide Complexes of Octamethyl Calix[4]Pyrrole

Ion receptors are molecular hosts that bind ionic guests, often with great selectivity. The interplay of solvation and ion binding in anion host-guest complexes in solution governs the binding efficiency and selectivity of such ion receptors. To gain molecular-level insight into the intrinsic binding properties of octamethyl calix[4]pyrrole (omC4P) host molecules with halide guest ions, we performed cryogenic ion vibrational spectroscopy (CIVS) of omC4P in complexes with fluoride, chloride, and bromide ions. We interpret the spectra using density functional theory, describing the infrared spectra of these complexes with both harmonic and anharmonic second-order vibrational perturbation theory (VPT2) calculations. The NH stretching modes of the pyrrole moieties serve as sensitive probes of the ion binding properties, as their frequencies encode the ion-receptor interactions. While scaled harmonic spectra reproduce the experimental NH stretching modes of the chloride and bromide complexes in broad strokes, the high proton affinity of fluoride introduces strong anharmonic effects. As a result, the spectrum of F-·omC4P is not even qualitatively captured by harmonic calculations, but it is recovered very well by VPT2 calculations. In addition, the VPT2 calculations recover the intricate coupling of the NH stretching modes with overtones and combination bands of CH stretching and NH bending modes and with low-frequency vibrations of the omC4P macrocycle, which are apparent for all of the halide ion complexes investigated here. A comparison of the CIVS spectra with infrared spectra of solutions of the same ion-receptor complexes in d3-acetonitrile and d6-acetone shows how ion solvation changes the ion-receptor interactions for the different halide ions.

Narcissistic self-sorting in Zn(II) porphyrin derived semiconducting nanostructures

The narcissistic self-sorted phenomenon is explicitly attributed to the structural similarities in organic molecules. Although such relevant materials are rarely explored, self-sorted structures from macrocyclic π-conjugated-based p- and n-type organic semiconductors facilitate the increase of exciton dissociation and charge separation in bulk heterojunction solar cells. Herein, we report two extended π-conjugated derivatives consisting of zinc-porphyrin-linked benzothiadiazole acting as an acceptor (PB) and anthracene as a donor (PA). Despite having the same porphyrin π-conjugated core in PA and PB, variations in donor and acceptor moieties make the molecular packing form one-dimensional (1D) self-assembled nanofibers via H- and J-type aggregates. Interestingly, a dissimilar aggregate of PA and PB exists as a mixture (PA + PB), promoting narcissistic self-sorted structures. Electrochemical impedance investigation reveals that the electronic characteristics of self-sorting assemblies are influenced by the difference in electrostatic potentials for PA and PB, resulting in a transitional electrical conductivity of 0.14 S cm-1. Therefore, the design of such materials for the fabrication of effective photovoltaics is promoted by these extraordinary self-sorted behaviors in comparable organic π-conjugated molecules.

Responsive Supramolecular Polymers for Diagnosis and Treatment

Stimuli-responsive supramolecular polymers are ordered nanosized materials that are held together by non-covalent interactions (hydrogen-bonding, metal-ligand coordination, π-stacking and, host-guest interactions) and can reversibly undergo self-assembly. Their non-covalent nature endows supramolecular polymers with the ability to respond to external stimuli (temperature, light, ultrasound, electric/magnetic field) or environmental changes (temperature, pH, redox potential, enzyme activity), making them attractive candidates for a variety of biomedical applications. To date, supramolecular research has largely evolved in the development of smart water-soluble self-assemblies with the aim of mimicking the biological function of natural supramolecular systems. Indeed, there is a wide variety of synthetic biomaterials formulated with responsiveness to control and trigger, or not to trigger, aqueous self-assembly. The design of responsive supramolecular polymers ranges from the use of hydrophobic cores (i.e., benzene-1,3,5-tricarboxamide) to the introduction of macrocyclic hosts (i.e., cyclodextrins). In this review, we summarize the most relevant advances achieved in the design of stimuli-responsive supramolecular systems used to control transport and release of both diagnosis agents and therapeutic drugs in order to prevent, diagnose, and treat human diseases.

Distinction and Quantification of Noncovalent Dispersive and Hydrophobic Effects

The possibilities of comparing computational results of noncovalent interactions with experimental data are discussed, first with respect to intramolecular interactions. For these a variety of experimental data such as heats of formation, crystal sublimation heats, comparison with energy minimized structures, and spectroscopic data are available, but until now largely have not found widespread application. Early force field and QM/MP2 calculations have already shown that the sublimation heats of hydrocarbons can be predicted with an accuracy of ±1%. Intermolecular interactions in solution or the gas phase are always accompanied by difficult to compute entropic contributions, like all associations between molecules. Experimentally observed T∆S values contribute 10% to 80% of the total ∆G, depending on interaction mechanisms within the complexes, such as, e.g., hydrogen bonding and ion pairing. Free energies ∆G derived from equilibrium measurements in solution allow us to define binding increments ∆∆G, which are additive and transferable to a variety of supramolecular complexes. Data from more than 90 equilibrium measurements of porphyrin receptors in water indicate that small alkanes do not bind to the hydrophobic flat surfaces within a measuring limit of ∆G = ±0.5 kJ/mol, and that 20 functions bearing heteroatoms show associations by dispersive interactions with up to ∆G = 8 kJ/mol, roughly as a function of their polarizability. Aromatic systems display size-dependent affinities ∆G as a linear function of the number of π-electrons.

A Kinetic Investigation of the Supramolecular Chiral Self-Assembling Process of Cationic Organometallic (2,2':6',2″-terpyridine)methylplatinum(II) Complexes with Poly(L-glutamic Acid)

The cationic platinum(II) organometallic complex [Pt(terpy)Me]+ (terpy = 2,2':6',2″-terpyridine) at mild acidic pH interacts with poly(L-glutamic acid) (L-PGA) in its α-helix conformation, affording chiral supramolecular adducts. Their kinetics of formation have been investigated in detail as a function of the concentrations of both reagents and changing pH, ionic strength, the length of the polymeric scaffold and temperature. After a very fast early stage, the kinetic traces have been analyzed as three consecutive steps, suggesting a mechanism based on the electrostatic fast formation of a not-organized aggregate that subsequently evolves through different rearrangements to form the eventual supramolecular adduct. A model for this species has been proposed based on (i) the attractive electrostatic interaction of the cationic platinum(II) complexes and the polyelectrolyte and (ii) the π-stacking interactions acting among the [Pt(terpy)Me]+ units.

Solution-state mechanochromic luminescence of Pt(ii)-complexes displayed within micellar aromatic capsules

Mechanochromic luminescence (MCL) is an intrinsic phenomenon in the solid state and thus has been hardly observed in solution so far. Here we report that arylethynyl Pt(ii)-complexes with an NCN-pincer ligand are efficiently encapsulated by micellar aromatic capsules in water, through a simple grinding protocol with bent amphiphiles. When a bent pentamethylbenzene-based amphiphile is employed as an optimized capsule component, the resultant host-guest composite, with an average diameter of ∼4 nm, is obtained in water at room temperature. Notably, the nanocomposite displays strong red emission (Φ = 33%, λmax = 700 nm) derived from MCL via intermolecular Pt(ii)⋯Pt(ii) interactions even under aerobic aqueous conditions, in sharp contrast to the free Pt(ii)-complex with weak green emission (Φ = 4%, λmax = 500 nm) in CH2Cl2. Moreover, enhancement of the solution-state MCL (up to Φ = 48%) can be achieved by coencapsulation of the Pt(ii)-complexes with carbazole derivatives by the capsule in water. This study provides the first example of "solution-state" mechanochromic luminescence, capable of facilely tuning its intensity and wavelength, among the intensive studies of various solid-state MCL reported previously.

Precise Recognition in Water by an Endo-Functionalized Cavity: Tuning the Complementarity of Binding Sites

Precise binding towards structurally similar substrates is a common feature of biomolecular recognition. However, achieving such selectivity-especially in distinguishing subtle differences in substrates-with synthetic hosts can be quite challenging. Herein, we report a novel design strategy involving the combination of different rigid skeletons to adjust the distance between recognition sites within the cavity, which allows for the highly selective recognition of hydrogen-bonding complementary substrates, such as 4-chromanone. X-ray single-crystal structures and density functional theory calculations confirmed that the distance of endo-functionalized groups within the rigid cavity is crucial for achieving high binding selectivity through hydrogen bonding. The thermodynamic data and molecular dynamics simulations revealed a significant influence of the hydrophobic cavity on the binding affinity. The new receptor possesses both high selectivity and high affinity, which provide valuable insights for the design of customized receptors.

Synthesis, supramolecular aggregation, and NIR-II phosphorescence of isocyanorhodium(i) zwitterions

Development of new second near-infrared (NIR-II, 1000-1700 nm) luminophores is highly desirable, and d8 square-planar metal complexes with NIR-II phosphorescence have been rarely reported. Herein, we explore an asymmetric coordination paradigm to achieve the first creation of NIR-II phosphorescent isocyanorhodium(i) zwitterions. They show a strong tendency for aggregation in solution, arising from close Rh(i)⋯Rh(i) contacts that are further intensified by π-π stacking interactions and the hydrophilic-hydrophobic effect. Based on such supramolecular aggregation, zwitterions 2 and 5 are found to yield NIR-II phosphorescence emissions centered at 1005 and 1120 (1210, shoulder) nm in methanol-water mixed solvents, respectively. These two bands show red shifts to 1070 and 1130 (1230, shoulder) nm in the corresponding polymer nanoparticles in water. The resulting polymer nanoparticles can brighten in vivo tumor issues in the NIR-II region with a long-circulating time. In view of the synthetic diversity established by the asymmetric coordination paradigm, this work provides an extraordinary opportunity to explore NIR-II luminophores.

An artificial light-harvesting system constructed from a water-soluble metal-organic barrel for photocatalytic aerobic reactions in aqueous media

An artificial light-harvesting system constructed from a water-soluble host-guest complex can be regarded as a high-level conceptual model of its biological counterpart and can convert solar energy into chemical energy in an aqueous environment. Herein, a water-soluble metal-organic barrel Ga-tpe with twelve sulfonic acid units was obtained by subcomponent self-assembly between Ga3+ ions and tetra-topic ligands with tetraphenylethylene (TPE) cores. By taking advantage of host-guest interactions, cationic dye rhodamine B (RB) was constrained in the pocket of Ga-tpe to promote the Förster resonance energy transfer (FRET) process for efficient photocatalytic aerobic oxidation of sulfides and cross-dehydrogenative coupling (CDC) reaction in aqueous media.

Porous Supramolecular Assemblies for Efficient Suzuki Coupling of Aryl Chlorides

The development of catalytic systems that can activate aryl chlorides for palladium-catalyzed cross-coupling reactions is at the forefront of ongoing efforts to synthesize fine chemicals. In this study, a facile ligand-template approach is adopted to achieve active-site encapsulation by forming supramolecular assemblies; this bestowed the pristine inert counterparts with reactivity, which is further increased upon the construction of a porous framework. Experimental results indicated that the isolation of ligands by the surrounding template units is key to the formation of catalytically active monoligated palladium complexes. Additionally, the construction of porous frameworks using the resulting supramolecular assemblies prevented the decomposition of the Pd complexes into nanoparticles, which drastically increased the catalyst lifetime. These findings, along with the simplicity and generality of the synthesis scheme, suggest that the strategy can be leveraged to achieve unique reactivity and potentially enable fine-chemical synthesis.

Synthesis and Host-Guest Chemistry of Chiral Spirobifluorene-Based Macrocycles Soluble in Basic Aqueous Solution

Synthesis and host-guest chemistry of water-soluble (pH 12.5) chiral spirobifluorene-based macrocycles 2-[n] were carried out. Cationic guests, such as quaternary ammonium salts, were accommodated well in the hosts. Cp2Co+ was especially strongly bound in 2-[4] (Ka of up to 3.0 × 105 M-1). Enantioselective recognition with (l)-carnitine was also achieved.

Aqueous Three-Component Self-Assembly of a Pseudo[1]rotaxane Using Hydrazone Bonds

We present herein the synthesis of a new polycationic pseudo[1]rotaxane, self-assembled in excellent yield through hydrazone bonds in aqueous media of three different aldehyde and hydrazine building blocks. A thermodynamically controlled process has been studied sequentially by analyzing the [1 + 1] reaction of a bisaldehyde and a trishydrazine leading to the macrocyclic part of the system, the ability of this species to act as a molecular receptor, the conversion of a hydrazine-pending cyclophane into the pseudo[1]rotaxane and, lastly, the one-pot [1 + 1 + 1] condensation process. The latter was found to smoothly produce the target molecule through an integrative social self-sorting process, a species that was found to behave in water as a discrete self-inclusion complex below 2.5 mM concentration and to form supramolecular aggregates in the 2.5-70 mM range. Furthermore, we demonstrate how the abnormal kinetic stability of the hydrazone bonds on the macrocycle annulus can be advantageously used for the conversion of the obtained pseudo[1]rotaxane into other exo-functionalized macrocyclic species.

Exploration of molecular machines in supramolecular soft robotic systems

Soft robotic system, a new era of material science, is rapidly developing with advanced processing technology in soft matters, featured with biomimetic nature. An important bottom-up approach is through the implementation of molecular machines into polymeric materials, however, the synchronized molecular motions, acumination of strain across multiple length-scales, and amplification into macroscopic actuations remained highly challenging. This review presents the significances, key design strategies, and outlook of the hierarchical supramolecular systems of molecular machines to develop novel types of supramolecular-based soft robotic systems.

The "Nitrogen Effect": Complexation with Macrocycles Potentiates Fused Heterocycles to Form Halogen Bonds in Competitive Solvents

Weak intermolecular forces are typically very difficult to observe in highly competitive polar protic solvents as they are overwhelmed by the quantity of competing solvent. This is even more challenging for three-component ternary assemblies of pure organic compounds. In this work, we overcome these complications by leveraging the binding of fused aromatic N-heterocycles in an open resorcinarene cavity to template the formation of a three-component halogen-bonded ternary assembly in a protic polar solvent system.

Confinement effect on hydrolysis in small lipid vesicles

In living organisms most chemical reactions take place within the confines of lipid-membrane bound compartments, while confinement within the bounds of a lipid membrane is thought to be a key step in abiogenesis. In previous work we demonstrated that confinement in the aqueous cavity of a lipid vesicle affords protection against hydrolysis, a phenomenon that we term here confinement effect (C _e) and that we attributed to the interaction with the lipid membrane. Here, we show that both the size and the shape of the cavity of the vesicle modulate the C _e. We link this observation to the packing of the lipid following changes in membrane curvature, and formulate a mathematical model that relates the C _e to the radius of a spherical vesicle and the packing parameter of the lipids. These results suggest that the shape of the compartment where a molecule is located plays a major role in controlling the chemical reactivity of non-enzymatic reactions. Moreover, the mathematical treatment we propose offers a useful tool for the design of vesicles with predictable reaction rates of the confined molecules, e.g., drug delivery vesicles with confined prodrugs. The results also show that a crude form of signal transduction, devoid of complex biological machinery, can be achieved by any external stimuli that drastically changes the structure of the membrane, like the osmotic shocks used in the present work.

Protein-protein interaction and interference of carcinogenesis by supramolecular modifications

Protein-protein interactions (PPIs) are essential in normal biological processes, but they can become disrupted or imbalanced in cancer. Various technological advancements have led to an increase in the number of PPI inhibitors, which target hubs in cancer cell's protein networks. However, it remains difficult to develop PPI inhibitors with desired potency and specificity. Supramolecular chemistry has only lately become recognized as a promising method to modify protein activities. In this review, we highlight recent advances in the use of supramolecular modification approaches in cancer therapy. We make special note of efforts to apply supramolecular modifications, such as molecular tweezers, to targeting the nuclear export signal (NES), which can be used to attenuate signaling processes in carcinogenesis. Finally, we discuss the strengths and weaknesses of using supramolecular approaches to targeting PPIs.

Supramolecular Recognition of Phosphodiester-Based Donor and Acceptor Oligomers Forming Gels in Water

Inspired by automated DNA synthesis, electron-rich dialkoxynaphthalene (DAN) donor and electron-deficient naphthalene-tetracarboxylic diimide (NDI) acceptor phosphodiester-linked homohexamers were synthesized by the phosphoramidite method. Two types of hexamers were prepared, one with only one phosphodiester between the aromatics (i.e., DAN or NDI) and a second with two phosphodiesters around a propanediol between the aromatics, leading to the latter more flexible and more hydrophilic hexamers. The folding properties of these homohexamers alone or mixed together, in water only, were studied by UV-visible absorption spectroscopy and atomic force microscopy (AFM). AFM imaging revealed that a 1:1 mixture of hexaDAN and hexaNDI formed fibers by charge transfer donor-acceptor recognition leading to a hydrogel after drying. The organization of the resulting structures is strongly dependent on the nature of the complementary partner, leading to the formation of mono- or multilayer hydrogel networks with different compactness.

Tricyclic octaurea "Temples" for the recognition of polar molecules in water

Two water-soluble tricyclic "Temple" macrocycles featuring pyrene roof/floor units and bis-urea spacers have been synthesised and studied as receptors for aromatic compounds in aqueous media. The tricycles show good selectivity for methylated purine alkaloids such as caffeine versus unsubstituted heterocycles such as adenine and indole. Binding is signalled by major changes in fluorescence, apparently due to the break-up of intramolecular excimers. The formation of excimers implies cavity collapse in the absence of guests explaining why, unlike an earlier relative, these receptors do not bind carbohydrates. Naphthalenediimides (NDIs) have also been studied as geometrically complementary guests, and indeed bind especially strongly (K_a > 10⁷ M^-1); this powerful and selective association suggests potential applications in supramolecular self-assembly.

An intelligent peptide recognizes and traps Mycobacterium tuberculosis to inhibit macrophage phagocytosis

Tuberculosis is a major public health concern worldwide, and it is a serious threat to human health for a long period. Macrophage phagocytosis of Mycobacterium tuberculosis (M. tuberculosis) is a crucial process for granuloma formation, which shelters the bacteria and gives them an opportunity for re-activation and spread. Herein, we report an intelligent anti-microbial peptide that can recognize and trap the M. tuberculosis, inhibiting the macrophage phagocytosis process. The peptide (Bis-Pyrene-KLVFF-WHSGTPH, in abbreviation as BFH) first self-assembles into nanoparticles, and then forms nanofibers upon recognizing and binding M. tuberculosis. Subsequently, BFH traps M. tuberculosis by the in situ formed nanofibrous networks and the trapped M. tuberculosis are unable to invade host cells (macrophages). The intelligent anti-microbial peptide can significantly inhibit the phagocytosis of M. tuberculosis by macrophages, thereby providing a favorable theoretical basis for inhibiting the formation of tuberculosis granulomas.

Enhanced molecular binding affinity toward aromatic dications by anthracene-derived crown ethers in water

The pursuit of high molecular binding affinity using conventional crown ethers in water remains a challenging task in the field of supramolecular chemistry and may hold great promise in the creation of advanced biocompatible nanoconstructs. In this work, the molecular binding strength toward a series of structurally relevant cationic guests has been greatly enhanced by tetrasulfonated 1,5-dianthracenyl-42-crown-10 and as investigated by means of ¹H NMR, UV-vis, and fluorescence spectroscopy, the host-guest association constants can reach up to 10⁸ M^-1 order of magnitude in aqueous solution. X-ray crystal diffraction analysis further demonstrates that the aromatic dication can be tightly encapsulated in the ring of anthracene-derived crown ether via multiple π-stacking and electrostatic interactions. Meanwhile, the obtained association constants are remarkably higher than the ones in the cases of the known benzene- and naphthalene-derived sulfonated crown ethers, substantiating that the appropriate extension of π-conjugation in the molecular skeleton of crown ether is a feasible method in attaining a highly affiliative host-guest complex. Taken together, our results indicate that the anthracene-based sulfonated crown ether can be developed as a new family of water-soluble macrocyclic receptors in the fabrication of functional nanoarchitectures.

Mitochondrial Aging and Senolytic Natural Products with Protective Potential

Living organisms do not disregard the laws of thermodynamics and must therefore consume energy for their survival. In this way, cellular energy exchanges, which aim above all at the production of ATP, a fundamental molecule used by the cell for its metabolisms, favor the formation of waste products that, if not properly disposed of, can contribute to cellular aging and damage. Numerous genes have been linked to aging, with some favoring it (gerontogenes) and others blocking it (longevity pathways). Animal model studies have shown that calorie restriction (CR) may promote longevity pathways, but given the difficult application of CR in humans, research is investigating the use of CR-mimetic substances capable of producing the same effect. These include some phytonutrients such as oleuropein, hydroxytyrosol, epigallo-catechin-gallate, fisetin, quercetin, and curcumin and minerals such as magnesium and selenium. Some of them also have senolytic effects, which promote the apoptosis of defective cells that accumulate over the years (senescent cells) and disrupt normal metabolism. In this article, we review the properties of these natural elements that can promote a longer and healthier life.

Anisotropic Microgels by Supramolecular Assembly and Precipitation Polymerization of Pyrazole-Modified Monomers

Soft colloidal macromolecular structures with programmable chemical functionalities, size, and shape are important building blocks for the fabrication of catalyst systems and adaptive biomaterials for tissue engineering. However, the development of the easy upscalable and template-free synthesis methods to obtain such colloids lack in understanding of molecular interactions that occur in the formation mechanisms of polymer colloids. Herein, a computer simulation-driven experimental synthesis approach based on the supramolecular self-assembly followed by polymerization of tailored pyrazole-modified monomers is developed. Simulations for a series of pyrazole-modified monomers with different numbers of pyrazole groups, different length and polarity of spacers between pyrazole groups and the polymerizable group are first performed. Based on simulations, monomers able to undergo π-π stacking and guide the formation of supramolecular bonds between polymer segments are synthesized and these are used in precipitation polymerization to synthesize anisotropic microgels. This study demonstrates that microgel morphologies can be tuned from spherical, raspberry-like to dumbbell-like by the increase of the pyrazole-modified monomer loading, which is concentrated at periphery of growing microgels. Combining experimental and simulation results, this work provides a quantitative and predictive approach for guiding microgel design that can be further extended to a diversity of colloidal systems and soft materials with superior properties.

2-Hydroxychalcone-β-Cyclodextrin Conjugate with pH-Modulated Photoresponsive Binding Properties

Stimuli-responsive supramolecular receptors are important building blocks for the construction of self-assembled functional materials. We report the design and synthesis of a pH- and light-responsive 2-hydroxychalcone-β-cyclodextrin conjugate (1-Ct) and its characterization by spectroscopic and computational methods. 1-Ct follows the typical reaction network of trans-chalcone-flavylium photoswitches. Upon light irradiation, 1-Ct can be photochemically converted into the cis-chalcone/hemiketal forms (1-Cc/1-B) under neutral pH conditions or to the flavylium cation (1-AH⁺) at acidic pH values. This stimuli-responsive β-cyclodextrin host, 1-Ct, was found to form stronger intramolecular self-inclusion complexes (K_intra = 14) than 1-AH⁺ (K_intra = 3) and weaker than 1-Cc/1-B (overall K_intra = 179), allowing control over their stability and binding properties by combinations of pH and light stimuli.

Specific Binding of Primary Ammoniums in Aqueous Media by Homooxacalixarenes Incorporated into Micelles

The development of artificial receptors for efficient recognition of analytes in water is a challenging task. Homooxacalix[3]arene-based receptor 1, which is selective toward primary ammoniums in organic solvents, was transferred into water following two different strategies: direct solubilization and micellar incorporation. Extensive ¹H NMR studies showed that recognition of ammoniums is only observed in the case of micellar incorporation, highlighting the beneficial effect of the microenvironment of the micellar core. The selectivity of the system for primary ammoniums over secondary and tertiary ones was also maintained. The hydrophobic effect plays an important role in the recognition properties, which are counterion-dependent due to the energy penalty for the dissociation of certain ammonium salts in the apolar micellar core. This study shows that the straightforward self-assembly process used for the encapsulation of artificial receptors in micelles is an efficient strategy for developing water-soluble nanosized supramolecular recognition systems.

Supramolecular Rotaxane‐Based Multi‐Modal Probes for Cancer Biomarker Imaging**

Mechanically interlocked molecules present opportunities to construct therapeutic drugs and diagnostic imaging agents but harnessing supramolecular chemistry to make biologically active probes in water is a challenge. Here, we describe a rotaxane‐based approach to synthesise radiolabelled proteins and peptides for molecular imaging of cancer biomarkers in vivo. Host–guest chemistry using β‐cyclodextrin‐ and cucurbit[6]uril‐catalysed cooperative capture synthesis produced gallium‐68 or zirconium‐89 radiolabelled metallo[4]rotaxanes. Photochemical conjugation to trastuzumab led to a viable positron emission tomography (PET) radiotracer. The rotaxane architecture can be tuned to accommodate different radiometal ion complexes, other protein‐ or peptide‐based drugs, and fluorophores for optical detection. This technology provides a platform to explore how mechanical bonding can improve drug delivery, enhance tumour specificity, control radiotracer pharmacokinetics, and reduce dosimetry.

Modeling and Optimisation of Comlexity by the β-Cyclodextrin of an Organic Pollutant Model: m-Methyl Red

Studies of cyclodextrin chemistry using quantum chemical methods are mainly adopted to investigate the formation of the inclusion complex causing changes in the physicochemical properties of the cyclodextrin guest. In this paper, we conducted a computational modeling study of the inclusion complexes of β-cyclodextrin (β-CD) with m-Methyl Red (m-MR) by using parametric method 6 (PM6), the semi empirical molecular orbital calculations and the natural bond orbital method (NBO). The inclusion process is carried out by maintaining the coordinates of the β-CD fixed and by displacing the guest molecule. The different relative positions between m-MR and β-CD are measured with respect to the distance between the reference atom (N) in the guest molecule and the origin of the coordinates from the equatorial plane of β-CD. The m-MR/β-CD (B) inclusion complex has a lower negative value of ΔG compared to another m-MR/β-CD (A) complex, highlighting the spontaneous behavior of the inclusion process. In addition, during the process of inclusion, the complexation energy is negative, which allows us to affirm that the complexation of m-MR in the β-CD is thermodynamically favorable. Among two directions A and B, the minimum energy generated from the PM6 was obtained in the orientation B and the guest molecule is partially encapsulated in the cavity of β-CD. In the NBO analysis, the stabilization energy is also usually used to characterize the hydrogen bond interaction between a lone pair (LP(Y)) of an atom Y and an anti-bonding orbital (BD٭(X-H)).

Recent Advances in the Applications of Water-soluble Resorcinarene-based Deep Cavitands

We review here the use of container molecules known as cavitands for performing organic reactions in water. Central to these endeavors are binding forces found in water, and among the strongest of these is the hydrophobic effect. We describe how the hydrophobic effect can be used to drive organic molecule guests into the confined space of cavitand hosts. Other forces participating in guest binding include cation-π interactions, chalcogen bonding and even hydrogen bonding to water involved in the host structure. The reactions of guests take advantage of their contortions in the limited space of the cavitands which enhance macrocyclic and site-selective processes. The cavitands are applied to the removal of organic pollutants from water and to the separation of isomeric guests. Progress is described on maneuvering the containers from stoichiometric participation to roles as catalysts.

A fluorescent, chirality-responsive, and water-soluble cage as a multifunctional molecular container for drug delivery

In recent years, the rational design and construction of drug delivery systems (DDSs) via a supramolecular approach for improving chemical therapeutics have gained significant attention. Here, we report a host-guest DDS formed from a fluorescent, chirality-responsive, and water-soluble tetraphenylethene-based octacationic cage as a fluorescent/chiral probe, solubilizer, and molecular cargo, which can recognize chiral nucleoside drugs, enhance the solubility of insoluble drugs, and protect drugs from the outside environment by forming host-guest complexes in aqueous solution. Given the fluorescence properties and dynamically rotational conformation of tetraphenylethene (TPE) units, this fluorescent and chirality-responsive cage exhibits different responses including turn-on/turn-off fluorescence and negative/positive circular dichroism (CD) when binding with different chiral nucleoside drugs in water, resulting in multiple-responsive photophysical behaviors for these chiral drugs. Furthermore, this water-soluble cationic cage with a hydrophobic cavity can improve the water solubility of insoluble drugs (e.g., CPT) by forming host-guest complexes in water. More importantly, this multifunctional cage exhibits a low toxicity to both human colon and breast cancer cell lines in vitro, and drugs encapsulated by the cage are more effective in killing cancer cells than drugs alone. Finally, the on-off-on fluorescence responses in the formation and dissociation processes of the cage⊃drug complexes have been successfully used to monitor drug release and track drug delivery by fluorescence microscopy in vitro. Therefore, this fluorescent, chirality-responsive, and water-soluble cage as a multifunctional molecular container can be used to construct a smart drug delivery system with several functions of fluorescence and CD detection, water solubilization, real-time monitoring, and chemotherapy.

Challenges, Prospects, and Emerging Applications of Inkjet-Printed Electronics: A Chemist's Point of View

Driven by the development of new functional inks, inkjet-printed electronics has achieved several milestones upon moving from the integration of simple electronic elements (e.g., temperature and pressure sensors, RFID antennas, etc.) to high-tech applications (e.g. in optoelectronics, energy storage and harvesting, medical diagnosis). Currently, inkjet printing techniques are limited by spatial resolution higher than several micrometers, which sets a redhibitorythreshold for miniaturization and for many applications that require the controlled organization of constituents at the nanometer scale. In this Review, we present the physico-chemical concepts and the equipment constraints underpinning the resolution limit of inkjet printing and describe the contributions from molecular, supramolecular, and nanomaterials-based approaches for their circumvention. Based on these considerations, we propose future trajectories for improving inkjet-printing resolution that will be driven and supported by breakthroughs coming from chemistry. Please check all text carefully as extensive language polishing was necessary. Title ok? Yes.

CB[7]- and CB[8]-Based [2]-(Pseudo)rotaxanes with Triphenylphosphonium-Capped Threads: Serendipitous Discovery of a New High-Affinity Binding Motif

The synthesis of new triphenylphosphonium-capped cucurbit[7]uril (CB[7])- and cucurbit[8]uril (CB[8])-based [2]rotaxanes was achieved by a simultaneous threading-capping strategy. While the use of CB[7] produced the designed [2]rotaxane, attempts to obtain the CB[8] analogue were unsuccessful due to the unexpected strong interaction found between the host and the phosphonium caps leading to pseudo-heteroternary host–guest complexes. This unusual binding motif has been extensively studied experimentally, with results in good agreement with those obtained by dispersion-corrected DFT methods.

Switchable bifunctional molecular recognition in water using a pH-responsive Endo-functionalized cavity

The construction of water-soluble synthetic hosts with a stimuli-responsive endo-functionalized cavity is challenging. These hosts feature a switchable cavity and may bring new properties to the fields of self-assembly, molecular machines, and biomedical sciences. Herein, we report a pair of water-soluble naphthotubes with a pH-responsive endo-functionalized cavity. The inward-directing secondary amine group of the hosts can be protonated and deprotonated. Thus, the hosts have different cavity features at the two states and show drastically different binding preference and selectivity in water. We reveal that the binding difference of the two host states is originated from the differences in charge repulsion, hydrogen bonding and the hydrophobic effects. Moreover, the guest binding can be easily switched in a ternary mixture with two guest molecules by adjusting the pH value of the solution. These pH-responsive hosts may be used for the construction of smart self-assembly systems and water-soluble molecular machines.

When Molecules Meet in Water-Recent Contributions of Supramolecular Chemistry to the Understanding of Molecular Recognition Processes in Water

Molecular recognition processes in water differ from those in organic solvents in that they are mediated to a much greater extent by solvent effects. The hydrophobic effect, for example, causes molecules that only weakly interact in organic solvents to stay together in water. Such water‐mediated interactions can be very efficient as demonstrated by many of the synthetic receptors discussed in this review, some of which have substrate affinities matching or even surpassing those of natural binders. However, in spite of considerable success in designing such receptors, not all factors determining their binding properties in water are fully understood. Existing concepts still provide plausible explanations why the reorganization of water molecules often causes receptor‐substrate interactions in water to be strongly exothermic rather than entropically favored as predicted by the classical view of the hydrophobic effect.

Molecular Approaches to Protein Dimerization: Opportunities for Supramolecular Chemistry

Protein dimerization plays a key role in many biological processes. Most cellular events such as enzyme activation, transcriptional cofactor recruitment, signal transduction, and even pathogenic pathways are significantly regulated via protein-protein interactions. Understanding and controlling the molecular mechanisms that regulate protein dimerization is crucial for biomedical applications. The limitations of engineered protein dimerization provide an opportunity for molecular chemistry to induce dimerization of protein in biological events. In this review, molecular control over dimerization of protein and activation in this respect are discussed. The well known molecule glue-based approaches to induced protein dimerization provide powerful tools to modulate the functionality of dimerized proteins and are shortly highlighted. Subsequently metal ion, nucleic acid and host-guest chemistry are brought forward as novel approaches for orthogonal control over dimerization of protein. The specific focus of the review will be on host-guest systems as novel, robust and versatile supramolecular approaches to modulate the dimerization of proteins, using functional proteins as model systems.

Aqueous Self-Assembly of Hydrophobic Molecules Influenced by the Molecular Geometry

Water, in addition to acting as a solvent, plays a constructional role in aqueous self-assembly. The hydrophobic molecule of POSS-PDI-POSS (POSS = polyhedral oligomeric silsesquioxanes, PDI = perylene diimide) has a shape anisotropy in which POSS is a ball-like bulky group and PDI is a flat aromatic group. The self-assembly of this molecule in water created assemblies with inner spaces due to the steric effect, which suppressed aromatic interactions of PDI and trapped water for the colloidal stability. By replacing POSS with dodecyl (C₁₂), C₁₂-PDI-C₁₂ aggregated with extended aromatic interaction of PDI and less inner water. The resulting aggregates tended to agglomerate and precipitate. This discovery extended the scope of aqueous self-assembly by using the building blocks without amphiphilicity and created knowledge for biophysics.

Thermoresponsive Supramolecular Assemblies from Dendronized Amphiphiles To Form Fluorescent Spheres with Tunable Chirality

Balance between self-association of structural units and self-repulsion from crowding-induced steric hindrance accounts for the supramolecular assembly of the amphiphilic entities to form ordered structures, and solvation provides a toolbox to conveniently modulate the assemblies through differential interactions to various structural units. Here we report solvation-modulated supramolecular chiral assembly in aqueous solutions of amphiphilic dendronized tetraphenylethylenes (TPEs) with three-folded dendritic oligoethylene glycols (OEGs) through dipeptide Ala-Gly linkage. These dendronized amphiphiles can form supramolecular spheres with enhanced supramolecular chirality, which is tunable and dependent on solvation. These nanosized spherical aggregates exhibit thermoresponsive behavior, and their cloud point temperatures are dependent on mixed solvent of water and THF. The phase transition temperatures increase with water fractions due to water-driven shifting of OEG moieties from interiors of the aggregates to their peripheries. Furthermore, the thermally induced dehydration and collapse of OEG moieties mediate the reversible aggregation and deaggregation between the spheres, imparting tunable aggregation-induced fluorescent emission (AIE) and supramolecular chirality. Both experimental results and molecular dynamic simulations have highlighted that reversible chirality transformations of the amphiphilic dendronized assemblies mediated by solvation through change solvent quality or thermally dehydration are dependent on the balance between interactions of OEG dendrons with TPE moieties and with the solvent molecules.

Molecular Recognition by Pillar[5]arenes: Evidence for Simultaneous Electrostatic and Hydrophobic Interactions

The formation of inclusion complexes between alkylsulfonate guests and a cationic pillar[5]arene receptor in water was investigated by NMR and ITC techniques. The results show the formation of host-guest complexes stabilized by electrostatic interactions and hydrophobic effects with binding constants of up to 10⁷ M⁻¹ for the guest with higher hydrophobic character. Structurally, the alkyl chain of the guest is included in the hydrophobic aromatic cavity of the macrocycle while the sulfonate groups are held in the multicationic portal by ionic interactions.