Self‐Assembly and Disassembly of Vesicles as Controlled by Anion–π Interactions

Carbon Dots Derived from Traditional Chinese Medicines with Bioactivities: A Rising Star in Clinical Treatment

In the field of carbon nanomaterials, carbon dots (CDs) have become a preferable choice in biomedical applications. Based on the concept of green chemistry, CDs derived from traditional Chinese medicines (TCMs) have attracted extensive attention, including TCM charcoal drugs, TCM extracts, and TCM small molecules. The design and preparation of CDs from TCMs (TCMs-CDs) can improve the inherent characteristics of TCMs, such as solubility, particle size distribution, and so on. Compared with other precursor materials, TCMs-CDs have outstanding intrinsic bioactivities and potential pharmacological effects. However, the research of TCMs-CDs in biomedicine is not comprehensive, and their mechanisms have not been understood deeply either. In this review, we will provide concise insights into the recent development of TCMs-CDs, with a major focus on their preparation, formation, precursors, and bioactivities. Then we will discuss the perfect transformation from TCMs to TCMs-CDs. Finally, we discuss the opportunities and challenges for the application of TCMs-CDs in clinical treatment.

Anion-π Interactions: What's in the Name?

The studies of the anion-π interactions advanced during the last two decades from the discussion of the mere existence of this counter-intuitive bonding to its utilization for anion recognition and transport, catalysis, and other applications. Yet, there are substantial differences in the interpretation of nature and the driving forces of anion-π bonding. Most surprisingly, there are still different opinions about the meaning of this term (i. e., which associations can be considered anion-π complexes). After a brief overview of the studies in this area (including early examples of such complexes), we suggested that anion-π bonding occurs when there is evidence of a net attraction between a (close-shell) anion and the face of an electrophilic π-system. This definition encompasses fundamentally similar supramolecular complexes comprising diverse π-systems and anions and its general acceptance would facilitate a discussion of the nature and distinct driving forces of this fascinating interaction.

Anion-π Interactions in Monolayers Formed by Amphiphilic Electron-Deficient Aromatic Compounds at Air/Water Interfaces

Biological systems precisely and selectively control ion binding through various chemical reactions, molecular recognition, and transport by virtue of effective molecular interactions with biological membranes and proteins. Because ion binding is inhibited in highly polar media, recognition systems for anions in aqueous media, which are relevant to biological and environmental systems, are still limited. In this study, we explored the anion binding of Langmuir monolayers formed by amphiphilic naphthalenediimide (NDI) derivatives with a series of substituents at air/water interfaces via anion-π interactions. Density functional theory (DFT) simulations revealed that the binding of anions originating from anion-π interactions is related to the electron density of the anions. At the air/water interfaces, amphiphilic NDI derivatives formed Langmuir monolayers, and the addition of anions caused expansion of the Langmuir monolayers. The anions with larger hydration energies related to electron density showed larger binding constants (K_a) for 1:1 stoichiometry with the NDI derivatives. The loosely packed monolayer formed by the amphiphilic NDI derivatives with bromine groups showed a better anion response. In contrast, the binding of NO₃^- was significantly enhanced in the highly packed monolayer. These results indicate that the packing of NDI derivatives with rigid aromatic rings influenced the binding of the anions. These results provide insight into ion binding using the air/water interface as a promising recognition site for mimicking biological membranes. In future, sensing devices can be developed using Langmuir-Blodgett films on electrodes. Furthermore, the capture of anions on electron-deficient aromatic compounds can lead to doping or composition technologies for n-type semiconductors.

Recognition competes with hydration in anion-triggered monolayer formation of cyanostar supra-amphiphiles at aqueous interfaces

The triggered self-assembly of surfactants into organized layers at aqueous interfaces is important for creating adaptive nanosystems and understanding selective ion extraction. While these transformations require molecular recognition, the underlying driving forces are modified by the local environment in ways that are not well understood. Herein, we investigate the role of ion binding and ion hydration using cyanosurf, which is composed of the cyanostar macrocycle, and its binding to anions that are either size-matched or mis-matched and either weakly or highly hydrated. We utilize the supra-amphiphile concept where anion binding converts cyanosurf into a charged and amphiphilic complex triggering its self-organization into monolayers at the air-water interface. Initially, cyanosurf forms aggregates at the surface of a pure water solution. When the weakly hydrated and size-matched hexafluorophosphate (PF6 -) and perchlorate (ClO4 -) anions are added, the macrocycles form distinct monolayer architectures. Surface-pressure isotherms reveal significant reorganization of the surface-active molecules upon anion binding while infrared reflection absorption spectroscopy show the ion-bound complexes are well ordered at the interface. Vibrational sum frequency generation spectroscopy shows the water molecules in the interfacial region are highly ordered in response to the charged monolayer of cyanosurf complexes. Consistent with the importance of recognition, we find the smaller mis-matched chloride does not trigger the transformation. However, the size-matched phosphate (H2PO4 -) also does not trigger monolayer formation indicating hydration inhibits its interfacial binding. These studies reveal how anion-selective recognition and hydration both control the binding and thus the switching of a responsive molecular interface.

The design of anion-π interactions and hydrogen bonds for the recognition of chloride, bromide and nitrate anions

The role of anions in several biochemical processes has given rise to enormous interest in the identification/exploration of compounds with the potential ability to recognize anions. Here, an anthracene-squaramide conjugated compound, O2C4[NH(C14H10)][(NH(C6H6)], has been modified through the substitutions (i) H → F and (ii) H → OH at the anthracene and benzene rings to improve the capabilities of these structures for recognizing chloride, bromide, and nitrate anions. Through an energy decomposition analysis method, the recognition of the anions is chiefly identified as a non-covalent process. H → F substitutions at the benzene ring and, principally, the anthracene ring favor anion recognition, since H → F substitutions create a π-acid region in the aromatic ring, as indicated based on the molecular electrostatic potential surfaces. Similarly, H → OH substitutions also improve the recognition of anions, which is related to the establishment of partly covalent chemical bonds of the form O-H(Cl-, Br- and O-), which are verified based on the quantitative analysis of the maximum and minimum values of the molecular electrostatic potential surfaces and the quantum theory of atoms in molecules method. The presence of large electron density has a key role in the recognition of Cl- anions, and the more favorable electrostatic interactions between the anthracene structure and Br- anions, relative to NO3- anions, mean that receptorBr- interactions are more attractive than receptorNO3- ones. These data can contribute to the design of structures with the relevant abilities to interact with anions.

Resonance-assisted/impaired anion-π interaction: towards the design of novel anion receptors

Substituents alter the electron density distribution in benzene in various ways, depending on their electron withdrawing and donating capabilities, as summarized by the empirical Hammett equation. The change of the π electron density distribution subsequently impacts the interaction of substituted benzenes or other cyclic conjugated rings with anions. Currently the design and synthesis of conjugated cyclic receptors capable of binding anions is an active field due to their applications in the sensing and removal of environmental contaminants and molecular recognition. By using the block-localized wavefunction (BLW) method, which is a variant of ab initio valence bond (VB) theory and can derive the reference resonance-free state self-consistently, we quantified the resonance-assisted (RA) or resonance-impaired (RI) phenomena in anion–π interactions from both structural and energetic perspectives. The frozen interaction, in which the electrostatic attraction is involved, has been shown to be the governing factor for the RA or RI interactions with anions. Energy analyses based on the empirical point charge (EPC) model indicated that the anion–π interactions can be simplified as the attraction between a negative point charge (anion) and a group of local dipoles, affected by the enriched or diminished π-cloud due to the resonance between the substituents and the conjugated ring. Hence, two strategies for the design of novel anion receptors can be envisioned. One is the enhancement of the magnitudes and/or numbers of local dipoles (polarized σ bonds), and the other is the reduction of π electron density in conjugated rings. For cases with the RI characteristics, “curved” aromatic molecules are preferred to be anion receptors. Indeed, extremely strong binding was found in complexes formed with fluorinated corannulene (F-CDD) and fluorinated [5]cycloparaphenylene (F-[5]CPP). Inspired by the RA phenomenon, complexes of p-, o- and m-benzoquinones with halides were revisited.

Substituents alter the electron density distribution in benzene in various ways, depending on their electron withdrawing and donating capabilities, as summarized by the empirical Hammett equation.

Enhancement of Ion Pairing of Sr(II) and Ba(II) Salts by a Tritopic Ion-Pair Receptor in Solution

Tritopic ion-pair receptors can bind bivalent salts in solution; yet, these salts have a tendency to form ion-pairs even in the absence of receptors. The extent to which such receptors can enhance ion pairing has however remained elusive. Here, we study ion pairing of M2+ (Ba2+ , Sr2+ ) and X- (I- , ClO4- ) in acetonitrile with and without a dichlorooxacalix[2]arene[2]triazine-related receptor containing a pentaethylene-glycol moiety. We find marked ion association already in receptor-free solutions. When present, most of the MX+ ion-pairs are bound to the receptor and the overall degree of ion association is enhanced due to coordinative, hydrogen-bonding, and anion-π interactions. The receptor shows higher selectivity for iodides but also stabilizes perchlorates, despite the latter are often considered as weakly coordinating anions. Our results show that ion-pair binding is strongly correlated to ion pairing in these solutions, thereby highlighting the importance of taking ion association in organic solvents into account.

Exploring Anion-π Interactions and Their Applications in Supramolecular Chemistry

Noncovalent bond interactions provide primary driving forces for supramolecular processes ranging from molecular recognition to self-assembly of sophisticated abiotic and biological machineries. While hydrogen bonding and π-π interactions are arguably textbook concepts playing indispensable parts in various scientific disciplines, noncovalent anion-π interactions have been emerging as attractive forces between π systems and negatively charged species for just about two decades. At the beginning of this century, three research groups reported independently their computational studies on the interactions between anions and aromatic compounds, proposing attractive anion-π interactions. Since π systems such as aromatic rings are traditionally noted as electron rich entities, anions and π systems would be repulsive to each other if there are any interactions. In stark contrast to the acknowledged cation-π interactions, the seemingly counterintuitive noncovalent anion-π bindings invoked great interest in the following years. Although a plethora of calculations had been published, the lack of experimental evidence cast doubt on the existence of anion-π interactions between anions and charge-neutral aromatic systems.During the same time when anion-π interactions were coined, we were studying the chemistry of novel macrocyclic compounds, namely, heteracalixaromatics, and their applications in supramolecular chemistry. It has been shown that heteracalixaromatics are powerful and versatile macrocyclic hosts to bind various guest species forming interesting assembled structures and organometallic complexes. Being a member of heteracalixaromatics, tetraoxacalix[2]arene[2]triaizne adopts a 1,3-alternate conformational structure yielding a V-shaped cavity or cleft formed by two electron-deficient triazine rings. Advantageously, the macrocycle is able to self-tune the cavity sizes by altering the degrees of conjugation between the bridging oxygen atoms with their bonded aromatic rings in response to the guest species in present, rendering it an ideal tool to explore anion-π interactions. We initiated our study on anion-π interactions using tetraoxacalix[2]arene[2]triazine as a molecular tool with the primary aim to clarify experimentally the uncertainty of whether exclusive anion-π interactions exist between anions and charge-neutral aromatic rings. We provided for the first time concrete evidence substantiating the formation of typical anion-π interaction between the anions and 1,3,5-triazine ring and demonstrated subsequently the generality and binding motifs of anion-π interactions. We have then extended our study to anion-π interaction-directed or -driven anion recognition and selective sensing, transmembrane anion transport, molecular self-assembly, and stimuli-responsive aggregation systems. A number of new generation macrocycles and cages constructed from electron-deficient tetrazine and benzenetriimide segments have also been developed in the meantime, advancing the study of anion-π interactions. This Account summarizes our endeavors to explore nascent anion-π interactions and their applications in supramolecular chemistry. We hope this Account will inspire scientists from various disciplines to explore all aspects of the nascent yet fruitful research area of anion-π interactions.

A ferrocene-templated Pd-bearing molecular reactor

High-yield, chromatography-free syntheses of a ferrocene-templated molecular cage and its Pd-bearing derivative are presented. The formation of a symmetric cage-type structure was confirmed by single-crystal X-ray diffraction analysis. The Pd-bearing cage was used as an innovative catalyst for the efficient synthesis of 1,1'-biphenyls under mild conditions. The presented catalyst is reusable and 1,1'-biphenyls can be obtained efficiently in a gram scale process.

An accurate single descriptor for ion-π interactions

Non-covalent interactions between ions and π systems play an important role in molecular recognition, catalysis and biology. To guide the screen and design for artificial hosts, catalysts and drug delivery, understanding the physical nature of ion-π complexes via descriptors is indispensable. However, even with multiple descriptors that contain the leading term of electrostatic and polarized interactions, the quantitative description for the binding energies (BEs) of ion-π complexes is still lacking because of the intrinsic shortcomings of the commonly used descriptors. Here, we have shown that the impartment of orbital details into the electrostatic energy (coined as OEE) makes an excellent single descriptor for BEs of not only spherical, but also multiply-shaped, ion-π systems, highlighting the importance of an accurate description of the electrostatic interactions. Our results have further demonstrated that OEEs from a low-level method could be calibrated to BEs from a high-level method, offering a powerful practical strategy for an accurate prediction of a set of ion-π interactions.

Switching of Self-Assembly to Solvent-Assisted Assembly of Molecular Motor: Unveiling the Mechanisms of Dynamic Control on Solvent Exchange

Natural biological molecular motors are capable of performing several biological functions, such as fuel production, mobility, transport, and many other dynamic features. Inspired by these biological motors, scientists effectively synthesized artificial molecular motors to mimic several biological functionalities. Several molecular systems, from sensitive materials to molecular motors, are essential for controlling dynamic processes in larger assemblies. In this work, we discuss the self-assembly of molecular motors in water and how this self-assembly switches to the solvent-assisted assembly as solvent changes to a water-THF (tetrahydrofuran) mixture. We present an elaborate description of the morphological changes of molecular motor assemblies from pure water to a water-THF mixture to pure THF. Under the influence of THF solvent, molecular motors form an assembled structure by taking a sufficient number of THF molecules in between themselves, resulting in an assembled molecular motor with a softened core. So, molecular motor assembly swells in the water-THF mixture, and in pure water, it shrinks. This solvent-assisted assembled structure has a specific shape. We have confirmed this assembly as a solvent-assisted assembly with the help of molecular dynamics simulation and quantum chemical analysis. Molecular motor-THF and THF-THF interactions are the main responsible interactions for solvent-assisted assembly over self-assembly. This work is a perfect example of conversion between self-assembly (shrinking) and solvent-assisted assembly (swelling) of molecular motors by adding THF into water or vice versa. A spectacular check on the shrinking and swelling by merely altering solvents illustrates so many intriguing possibilities for an alteration of dynamic processes at the nanoscale.

Macrocycle-Directed Construction of Tetrahedral Anion-π Receptors for Nesting Anions with Complementary Geometry

Manipulation of the emerging anion-π interactions in a highly cooperative manner through sophisticated host design represents a very challenging task. In this work, unprecedented tetrahedral anion-π receptors have been successfully constructed for complementary accommodation of tetrahedral and relevant anions. The synthesis was achieved by a macrocycle-directed approach by using large macrocycle precursors bearing four reactive sites, which enabled a kinetic-favored pathway and afforded the otherwise inaccessible tetrahedral cages in considerable yields. Crystal structure suggested that the tetrahedral cages have an enclosed three-dimensional cavity surrounded by four electron-deficient triazine faces in a tetrahedral array. The complementary accommodation of a series of tetrahedral and relevant anions including BF₄ ^- , ClO₄ ^- , H₂ PO₄ ^- , HSO₄ ^- , SO₄ ^2- and PF₆ ^- was revealed by ESI-MS and DFT calculations. Crystal structures of ClO₄ ^- and PF₆ ^- complexes showed that the anion was nicely encapsulated within the tetrahedral cavity with up to quadruple cooperative anion-π interactions by an excellent shape and size match. The strong anion-π binding was further confirmed by negative ion photoelectron spectroscopy measurements.

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

Functionalized O6-corona[3]arene[3]tetrazines were synthesized efficiently and conveniently by means of a macrocyclic condensation reaction between N-functionalized 3,6-dihydroxyphthalimides and 3,6-dichlorotetrazine under mild conditions in a one-pot reaction manner. The novel macrocycles exist as a mixture of rapidly interconvertible conformers in solution while in the solid state they adopt the conformation in which three phthalimide units are cis,trans-orientated. Acting as electron-deficient macrocyclic hosts, the synthesized O6-corona[3]arene[3]tetrazines self-regulated conformational structures to complex anions in the gas phase and in the solid state owing to the anion-π noncovalent interactions between anions and the tetrazine rings.

Macrocycles as Ion Pair Receptors

Cation and anion recognition have both played central roles in the development of supramolecular chemistry. Much of the associated research has focused on the development of receptors for individual cations or anions, as well as their applications in different areas. Rarely is complexation of the counterions considered. In contrast, ion pair recognition chemistry, emerging from cation and anion coordination chemistry, is a specific research field where co-complexation of both anions and cations, so-called ion pairs, is the center of focus. Systems used for the purpose, known as ion pair receptors, are typically di- or polytopic hosts that contain recognition sites for both cations and anions and which permit the concurrent binding of multiple ions. The field of ion pair recognition has blossomed during the past decades. Several smaller reviews on the topic were published roughly 5 years ago. They provided a summary of synthetic progress and detailed the various limiting ion recognition modes displayed by both acyclic and macrocyclic ion pair receptors known at the time. The present review is designed to provide a comprehensive and up-to-date overview of the chemistry of macrocycle-based ion pair receptors. We specifically focus on the relationship between structure and ion pair recognition, as well as applications of ion pair receptors in sensor development, cation and anion extraction, ion transport, and logic gate construction.

Anion–π interactions in lithium–organic redox flow batteries

The interactions between the electrolyte anions and electron-deficient redox-active organic molecules (anion–π interactions) have strong influences on the battery properties due to the anion–π-induced formation of radical anions or sandwich-like aggregates.

Synthesis, Structure, Property, and Dinuclear Cu(II) Complexation of Tetraoxacalix[2]arene[2]phenanthrolines

A number of novel tetraoxacalix[2]arene[2]phenanthrolines 7-11 containing phenanthroline and diverse aromatic linkages were conveniently synthesized by a one-pot protocol between a series of dihydroxy arenes and 1,10-phenanthroline derivatives. Single-crystal diffraction analysis revealed that the resulting macrocycles possess diverse conformational and cavity structures which are regulated by the different aromatic linkages. In line with the length of the aromatic linkages, the distance between the two phenanthroline moieties ( d_N-N) gradually increases from 6.92 to 13.30 Å, respectively. The physicochemical properties of these macrocyclic compounds were investigated by spectroscopic, CV, and DPV measurements. Owing to the coordination ability of the phenanthroline moieties and the tunable conformational structure, the macrocyclic hosts can form distinct dinuclear complexation with Cu²⁺. Typically, with a short aromatic linkage the 7b-2Cu(II) complex gives an O-bridged dicopper structure, while with long linkage the 11b-2Cu(II) complex possesses two discrete copper centers. The spectroscopic structure and the redox property of the dicopper complexes were investigated by XPS, CV, and DPV techniques. This work hence provides a platform to access biomimetic copper-containing small-molecule models with well-defined structures.

Remote Control of Anion-π Catalysis on Fullerene-Centered Catalytic Triads

The design, synthesis and evaluation of catalytic triads composed of a central C60 fullerene with an amine base on one side and polarizability enhancers on the other side are reported. According to an enolate addition benchmark reaction, fullerene-fullerene-amine triads display the highest selectivity in anion-π catalysis observed so far, whereas NDI-fullerene-amine triads are not much better than fullerene-amine controls (NDI=naphthalenediimide). These large differences in activity are in conflict with the small differences in intrinsic π acidity, that is, LUMO energy levels and π holes on the central fullerene. However, they are in agreement with the high polarizability of fullerene-fullerene-amine triads. Activation and deactivation of the fullerene-centered triads by intercalators and computational data on anion binding further indicate that for functional relevance, intrinsic π acidity is less important than induced π acidity, that is, the size of the oriented macrodipole of polarizable π systems that emerges only in response to the interaction with anions and anionic transition states. The resulting transformation is thus self-induced, the anionic intermediates and transition states create their own anion-π catalyst.

Solvent Mixing To Induce Molecular Motor Aggregation into Bowl-Shaped Particles: Underlying Mechanism, Particle Nature, and Application To Control Motor Behavior

Control over dynamic functions in larger assemblies is key to many molecular systems, ranging from responsive materials to molecular machines. Here we report a molecular motor that forms bowl-shaped particles in water and how confinement of the molecular motor affects rotary motion. Studying the aggregation process in a broader context, we provide evidence that, in the case of bowl-shaped particles, the structures are not the product of self-assembly, but a direct result of the mixing a good solvent and a (partial) non-solvent and highly independent of the molecular design. Under the influence of the non-solvent, droplets are formed, of which the exterior is hardened due to the increase in the glass transition temperature by the external medium, while the interior of the droplets remains plasticized by the solvent, resulting in the formation of stable bowl-shaped particles with a fluid interior, a glass-like exterior, and a very specific shape: dense spheres with a hole in their side. Applying this to a bulky first-generation molecular motor allowed us to change its isomerization behavior. Furthermore, the motor shows in situ photo-switchable aggregation-induced emission. Strong confinement prohibits the thermal helix inversion step while altering the energy barriers that determine the rotary motion, such that it introduces a reverse trans- cis isomerization upon heating. These studies show a remarkable control of forward and backward rotary motion by simply changing solvent ratios and extent of confinement.

From dynamic self-assembly to networked chemical systems

Although dynamic self-assembly, DySA, is a relatively new area of research, the past decade has brought numerous demonstrations of how various types of components - on scales from (macro)molecular to macroscopic - can be arranged into ordered structures thriving in non-equilibrium, steady states. At the same time, none of these dynamic assemblies has so far proven practically relevant, prompting questions about the field's prospects and ultimate objectives. The main thesis of this Review is that formation of dynamic assemblies cannot be an end in itself - instead, we should think more ambitiously of using such assemblies as control elements (reconfigurable catalysts, nanomachines, etc.) of larger, networked systems directing sequences of chemical reactions or assembly tasks. Such networked systems would be inspired by biology but intended to operate in environments and conditions incompatible with living matter (e.g., in organic solvents, elevated temperatures, etc.). To realize this vision, we need to start considering not only the interactions mediating dynamic self-assembly of individual components, but also how components of different types could coexist and communicate within larger, multicomponent ensembles. Along these lines, the review starts with the discussion of the conceptual foundations of self-assembly in equilibrium and non-equilibrium regimes. It discusses key examples of interactions and phenomena that can provide the basis for various DySA modalities (e.g., those driven by light, magnetic fields, flows, etc.). It then focuses on the recent examples where organization of components in steady states is coupled to other processes taking place in the system (catalysis, formation of dynamic supramolecular materials, control of chirality, etc.). With these examples of functional DySA, we then look forward and consider conditions that must be fulfilled to allow components of multiple types to coexist, function, and communicate with one another within the networked DySA systems of the future. As the closing examples show, such systems are already appearing heralding new opportunities - and, to be sure, new challenges - for DySA research.

Flexible imidazolium macrocycles: building blocks for anion-induced self-assembly

This feature article summarises recent contributions of the authors in the area of anion-induced supramolecular self-assembly. It is based on the chemistry of a set of tetracationic imidazolium macrocycles, specifically the so-called 'Texas-sized' molecular box, cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,4-dimethylenebenzene) (1⁴⁺), and its congeners, cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,2-dimethylenebenzene) (2⁴⁺), cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,3-dimethylenebenzene) (3⁴⁺), and cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](2,6-dimethylenepyridine) (4⁴⁺). These systems collectively have been demonstrated as being versatile building blocks that interact with organic carboxylate or sulfonate anions, as well as substrates (e.g., neutral molecules or metal cations). Most work to date has been carried out with 1⁴⁺, a system that has been found to support the construction of a number of stimuli responsive self-assembled ensembles. This macrocycle and others of the 'Texas-sized' box family also show the potential to react as carbene precursors and to undergo post-synthetic modification (PSM) to produce new functional macrocycles, such as trans- and cis-cyclo[2]((Z)-N-(2-((6-(1H-imidazol-1-yl)pyridin-2-yl)amino)vinyl)formamide)[2](1,4-bismethylbenzene) (5²⁺ and 6²⁺, respectively). On the basis of the work reviewed in this Feature article, we propose that the imidazolium macrocycles 1⁴⁺-4⁴⁺ can be considered as useful tools for the construction of ensembles with environmentally responsive features, including control over self-assembly and an ability to undergo precursor-specific PSM.

A supramolecular fluorescent vesicle based on a coordinating aggregation induced emission amphiphile: insight into the role of electrical charge in cancer cell division

Binding of Zn²⁺ to the coordinating supramolecular vesicle based on an aggregation induced emission amphiphile TPE-BPA immediately triggers the formation of charged vesicles. This induces vesicle fission and fluorescence reduction, suggesting a looser molecular packing in the charged vesicle membrane. Since cancer cells are highly charged, this indicates that the quick fission of cancer cells may have electrical charge origin.

Fingerprinting the Nature of Anions in Pyrylium Complexes: Dual Binding Mode for Anion-π Interactions

The interplay between noncovalent interactions that involve oxygenated heteroaromatic rings have been studied for the first time in this work. In particular, we report an advance in knowledge-based anion-π interactions together with (C-H)⁺ ⋅⋅⋅anion contacts. To understand how the anion modulates these interactions, the synthesis of pyrylium salts with a variety of anions was performed by using an anionic metathesis methodology. The synthesized pyrylium complexes were classified in series, for example, anions derived from halogens, from oxoacids, from p-block elements, and from transition metals. Crystallographic data, DFT calculations, and NMR spectroscopy methods provided access to an overall insight into the noncovalent behavior of the anion in this kind of system. Based on the DFT calculations and ¹ H NMR spectroscopy, pyrylium protons can be used as chemical tags to detect noncovalent interactions in this type of compound.