Cationic Assemblies Research Articles

Strain-Amplified Exciton Chirality in Organic-Inorganic Hybrid Materials.

Chiral organic-inorganic hybrids combining chirality of organic molecules and semiconducting properties of inorganic frameworks generate chiral excitons without external spin injection, creating the potential for chiroptoelectronics. However, the relationship between molecular chirality and exciton chirality is still unclear. Here we show the strain-amplified exciton chirality in one-dimensional chiral metal halides. Utilizing chirality-induced spin-orbital coupling theory, we quantitatively demonstrate the impact of the strain-engineered molecular assembly of chiral cations on exciton chirality, offering a feasible way to amplify exciton chirality by molecular manipulation.

Epoxidation of Olefins Catalyzed by Sulfate‐based Supramolecular Ion Pairs

AbstractThe development of inexpensive and effective catalysts for the epoxidation of olefins to epoxides, which are key commodities for the chemical industry, is a continuing challenge. In this context, we present a supramolecular solution with the development of new host‐guest assemblies of sulfate ions and amidoammonium receptor cations that, for the first time, are shown to act as catalysts for olefin epoxidation by hydrogen peroxide under biphasic conditions. Analysis of the reaction mechanism shows that the reactive and oxidizing peroxymonosulfate is formed in the organic phase. Furthermore, a variety of readily available precursors may be used to form the supramolecular ion pairs (SIPs), which is enabling a large‐scale synthesis of the catalysts while maintaining catalytic control and effectiveness.

Antibacterial Synthetic Nanocelluloses Synergizing with a Metal-Chelating Agent.

Antibacterial materials composed of biodegradable and biocompatible constituents that are produced via eco-friendly synthetic strategies will become an attractive alternative to antibiotics to combat antibiotic-resistant bacteria. In this study, we demonstrated the antibacterial properties of nanosheet-shaped crystalline assemblies of enzymatically synthesized aminated cellulose oligomers (namely, surface-aminated synthetic nanocelluloses) and their synergy with a metal-chelating antibacterial agent, ethylenediaminetetraacetic acid (EDTA). Growth curves and colony counting assays revealed that the surface-aminated cellulose assemblies had an antibacterial effect against Gram-negative Escherichia coli (E. coli). The cationic assemblies appeared to destabilize the cell wall of E. coli through electrostatic interactions with anionic lipopolysaccharide (LPS) molecules on the outer membrane. The antibacterial properties were significantly enhanced by the concurrent use of EDTA, which potentially removed metal ions from LPS molecules, resulting in synergistic bactericidal effects. No antibacterial activity of the surface-aminated cellulose assemblies was observed against Gram-positive Staphylococcus aureus even in the presence of EDTA, further supporting the contribution of electrostatic interactions between the cationic assemblies and anionic LPS to the activity against Gram-negative bacteria. Analysis using quartz crystal microbalance with dissipation monitoring revealed the attractive interaction of the surface-aminated cellulose assembly with LPS Ra monolayers artificially produced on the device substrate.

Ionothermal Approach to Homo- and Heteroleptic Alkylation of Tellurido Mercurate Clusters for Assembly in Lamellar Crystal Structures.

The selective methylation and butylation of chalcogenido metalate clusters by utilizing imidazolium-based ionic liquids turned out to be not only a comparably mild but at the same time also the only known method for postsynthetic alkylation of such species in order to increase their solubility. For additional impact on the crystal structures, selective alkylation with longer alkyl chains was addressed by utilizing the ionic liquid (C10C1Im)[BF4] (C10 = decyl group at position 1 and C1 = methyl group at position 3 of the cation's Im = imidazolium ring) for ionothermal syntheses of functionalized tellurido mercurate clusters. Herein, we report three novel compounds, two of which comprise cluster anions that exhibit a selective organic functionalization of their terminal telluride ligands upon in situ alkylation with the ionic liquid: [Hg6Te6(Te2)2(TeDec)2]6- (in 1; Dec = decyl) represents the first decylated chalcogenido metalate cluster. A unique heteroleptic functionalization, combining methylation and decylation, was achieved for the second cluster, [Hg6Te6(Te2)2(TeDec)(TeMe)]6- (in 2; Me = methyl). The third cluster is purely inorganic, but based on the same cluster core architecture: [Hg4Te2(Te2)2(Te3)2]4- (in 3) comprises a tritelluride unit instead of two HgTeR groups (R = Me, Dec). As a consequence of the long alkyl chains, both at the cluster and at the charge-compensating cations, all three crystal structures are characterized by lamellar assemblies of cations and anions. For further comparison of the properties of the organometallic versus purely inorganic compounds, vibrational and optical properties of crystalline samples of the compounds comprising clusters 1 and 3 were studied by means of infrared, Raman, and UV-visible spectroscopy. The results clearly show the effect of the presence of an organic decoration (in 1) relative to its absence (in 3), reflected by a red shift of the band gap energy (1 → 3) and a replacement of the Te-C bands (in 1) with bands for tritelluride units (in 3).

Large in-plane anisotropic 2D perovskites toward highly linear polarized light responses

A unique cationic assemblyviastrong H-bonding interacts intensely with perovskite inorganic sheets to bring about huge in-plane structural anisotropy that leads to high photocurrent anisotropy responses.

Functional Droplets Stabilized by Interfacially Self‐Assembled Chiral Nanocomposites

AbstractHere, we show that aqueous dispersions of inorganic nanoparticles bearing negative surface charges would trigger the chiral assembly of organic radical cations solubilized in organic solvent at the liquid–liquid interface, which consequently produces stable droplets covered by a layer of inorganic/organic chiral nanocomposites. We demonstrate that chirality transfer across the liquid–liquid interface from the chiral organic monomers to the nanoparticle assemblies is realized. Surprisingly, opposite handedness between molecular assemblies and nanoparticle assemblies is determined from both CD and CPL measurements. Moreover, the functionalities of these “chiral” droplets could be further engineered through either a simple mixing or a droplet merging strategy, which enables to produce fluorescent emissive‐tunable, magnetic, as well as magnetofluorescent dual‐functional droplets.

Functional Droplets Stabilized by Interfacially Self-Assembled Chiral Nanocomposites.

Here, we show that aqueous dispersions of inorganic nanoparticles bearing negative surface charges would trigger the chiral assembly of organic radical cations solubilized in organic solvent at the liquid-liquid interface, which consequently produces stable droplets covered by a layer of inorganic/organic chiral nanocomposites. We demonstrate that chirality transfer across the liquid-liquid interface from the chiral organic monomers to the nanoparticle assemblies is realized. Surprisingly, opposite handedness between molecular assemblies and nanoparticle assemblies is determined from both CD and CPL measurements. Moreover, the functionalities of these "chiral" droplets could be further engineered through either a simple mixing or a droplet merging strategy, which enables to produce fluorescent emissive-tunable, magnetic, as well as magnetofluorescent dual-functional droplets.

Simultaneous Identification of Multiple Binding Sites in Proteins: A Statistical Mechanics Approach.

We present an extension of the Poisson-Boltzmann model in which the solute of interest is immersed in an assembly of self-orienting Langevin water dipoles, anions, cations, and hydrophobic molecules, all of variable densities. Interactions between charges are controlled by electrostatics, while hydrophobic interactions are modeled with a Yukawa potential. We impose steric constraints by assuming that the system is represented on a cubic lattice. We also assume incompressibility; i.e., all sites of the lattice are occupied. This model, which we refer to as the Hydrophobic Dipolar Poisson-Boltzmann Langevin (HDPBL) model, leads to a system of two equations whose solutions give the water dipole, salt, and hydrophobic molecule densities, all of them in the presence of the others in a self-consistent way. We use those to study the organization of the ions, cosolvent, and solvent molecules around proteins. In particular, peaks of densities are expected to reveal, simultaneously, the presence of compatible binding sites of different kinds on a protein. We have tested and validated the ability of HDPBL to detect pockets in proteins that bind to hydrophobic ligands, polar ligands, and charged small probes as well as to characterize the binding sites of lipids for membrane proteins.

Anion-directed two cadmium(II) metal–organic frameworks based on bis(imidazol-1-yl)methane with diverse supramolecular structures and luminescence properties

Two Cd-based metal-organic frameworks derived from bis(imidazol-1-yl)methane (BIM), [Cd(BIM)2(NO3)2]n (complex 1) and {[Cd(BIM)2Cl2]•2H2O}n (complex 2), can be prepared and controlled by using different metal-dependent anions. BIM and Cd(NO3)2 can form a 1D framework based on CdN4(NO3)2 node. Cd(NO3)2 is replaced by CdCl2 to construct another 1D structure based on CdN4Cl2. It is notable that diverse structures of both complexes are mainly attributed to the metal-dependent anion effect during the assembly of metal cations and organic ligands. Meanwhile, complex 1 is used as a mode to explore the luminescent performance for nitrofurantoin (NFT) with preferable detectable ability and good reusability.

3D Metallo-organic coordination assembly-based anion-enriched supramolecular material for fast and efficient removal of Cr2O72−

Chromium(VI), especially dichromate (Cr2O72−) contamination in wastewater due to rapid industrialization with uncontrolled effluent management is still a serious concern which needs focused attention. Multiprong approaches are practiced such as chemical precipitation, reverse osmosis, ion-exchange, adsorption by granular activated carbon etc. to capture and separate this “Group A” human carcinogenic effluent from water. However, low capture capacity, non-reusability, poor selectivity, pH-limited performance are some major limitations of these techniques. Recently, metal organic frameworks (MOFs), metal organic cages (MOCs), porous organic polymers (POPs) or covalent organic frameworks (COFs), covalent organic networks (CONs) etc. emerged as new-generation materials to overcome such limitations. However, the development is still in initial stage and issues related to structural stability and integrity of many MOFs in water and in wide pH range, as well as reusability need to be addressed. At this juncture, herein we report a novel [Zn(terpyridine)2]2+-templated trisimidazolium-based highly cationic three-dimensional metal-organic coordination assembly (3D MOCA), serving as a new class of efficient, fast, robust and recyclable dichromate-removal material. Not only the highly cationic assembly is enriched with a high density of Br− anions, but its three-dimensional propagation and flexibility also exposes the exchangeable Br− ions for facile anion-metathesis with Cr2O72−. By virtue of the benefits of these attributes, the presented supramolecular material exhibits a high capture capacity (469 mg g−1), fast exchange kinetics (0.028 g mg−1 min−1), wide working pH range (pH 2–12) and reusability up to a minimum of 10 cycles without much loss of efficiency. Key mechanistic examinations highlight the evidences in favor of ion-exchange-based chemistry to be responsible for dichromate removal with the present material.

High Refractive-Index Hybrids Consisting of Water-Soluble Matrices with Bipyridine-Modified Polyhedral Oligomeric Silsesquioxane and Lanthanoid Cations.

We report high refractive-index (RI) films composed of polyhedral oligomeric silsesquioxane (SSQ) matrices and various lanthanoid cations. The SSQ matrices were constructed from octaammonium SSQ by connecting with bipyridine dicarboxylic acid, which is expected to capture cations. By modulating the feed ratio between SSQ and dicarboxylic acid, the series of the SSQ matrices were obtained with variable cross-linking ratios among the SSQ units. Thin transparent films were able to be prepared through the drop-casting method with the aqueous mixtures containing SSQ matrices and various kinds of lanthanoid salts up to 40 wt %. From RI measurements, it was revealed that the increase of the amount of the metal ion can significantly lift up the RI values. In particular, critical losses of Abbe numbers, which theoretically have the trade-off relationship toward increases in RI values, were hardly detected. This effect could be obtained by cation assembly in local spots that are assisted by SSQ.

Cationic Nanostructures for Vaccines Design.

Subunit vaccines rely on adjuvants carrying one or a few molecular antigens from the pathogen in order to guarantee an improved immune response. However, to be effective, the vaccine formulation usually consists of several components: an antigen carrier, the antigen, a stimulator of cellular immunity such as a Toll-like Receptors (TLRs) ligand, and a stimulator of humoral response such as an inflammasome activator. Most antigens are negatively charged and combine well with oppositely charged adjuvants. This explains the paramount importance of studying a variety of cationic supramolecular assemblies aiming at the optimal activity in vivo associated with adjuvant simplicity, positive charge, nanometric size, and colloidal stability. In this review, we discuss the use of several antigen/adjuvant cationic combinations. The discussion involves antigen assembled to (1) cationic lipids, (2) cationic polymers, (3) cationic lipid/polymer nanostructures, and (4) cationic polymer/biocompatible polymer nanostructures. Some of these cationic assemblies revealed good yet poorly explored perspectives as general adjuvants for vaccine design.

Dynamics of Chiral Cations in Two-Dimensional CuX4 and PbX4 Perovskites (X = Cl and Br).

Chiral organic ammonium cations ((R)-2-methylphenethylammonium (R-MPhA) and (R)-3,7-dimethyloctylammonium (R-DMOA)) cations were combined with [MX4]2- anions (M = Cu and Pb, X = Cl and Br) to form two-dimensional (2D) perovskites: (R-MPhA)2CuCl4 (1a), (R-MPhA)2CuBr4 (1b), (R-DMOA)2CuCl4 (2a), (R-DMOA)2CuBr4 (2b), (R-DMOA)2PbCl4 (2c), and (R-DMOA)2PbBr4 (2d). The point shearing of the MX4 octahedron formed 2D perovskite layers, which were sandwiched by the bilayer molecular assembly of chiral organic ammonium cations. We found that the flexible and polar organic R-MPhA and R-DMOA cations in the 2D perovskites played an important role in the phase transition behavior and dielectric responses. Salts 2a-2d showed similar solid-solid (S1-S2) phase transitions, for which the temperatures decreased in the order of CuCl4 (2a) > PbCl4 (2c) > CuBr4 (2b) > PbBr4 (2d). The occupation volume of one R-DMOA per MX4 octahedron determined the dynamic crystalline space for the motional freedom of chiral ammonium in the 2D perovskite layer. Although thermally activated dielectric fluctuations were observed in salts 2a, 2b, and 2c, only an order-disorder-type dielectric phase transition was observed in salt 2d. Interband optical transitions were observed in the CuCl4 and CuBr4 2D perovskites, whereas sharp exciton absorptions were observed in the 2D PbCl4 and PbBr4 layers in perovskite salts 2c and 2d.

Self-Assembled, Highly Positively Charged, Allyl-Pd Crowns: Cavity-Pocket-Driven Interactions of Fluoroanions.

A series of dodecanuclear highly positively charged homo- and heterometallamacrocycles [{Pd(η3 -2-Me-C3 H4 )}6 (4-PPh2 py)12 {M2 (tpbz)}3 ]18+ (M=Pd, Pt; tpbz=1,2,4,5-tetrakis(diphenylphosphanyl)benzene were synthesized by the quantitative self-assembly of {Pd(η3 -2-Me-C3 H4 )}+ , {M2 (tpbz)}4+ and 4-PPh2 py moieties in 2:1:4 molar ratio. The cationic assemblies were obtained as salts of different fluorinated anions with diverse sizes and electronic properties, namely BF4 - , PF6 - , SbF6 - and CF3 SO3 - . The new crown-like metallamacrocycles showed remarkable differences in their NMR spectra due to the presence of the different counteranions. On the basis of the observed variations, the metallacycles have been tested as catalytic precursors in allylic alkylation reactions. The anion-dependent activity and selectivity has been analysed and compared with that of the corresponding monometallic allylic corners [Pd(η3 -2-Me-C3 H4 )(4-PPh2 py)2 ]X (X=BF4 - , PF6 - , SbF6 - , CF3 SO3 - ). DFT calculations have been employed in order to help to the interpretation of the experimental data and to model the anion-crown interactions.

Halogen-Bond-Modulated Organization of [Ni(terpy-ph)2]I2 Complexes in Heteromeric Three-Component Systems

The encapsulation of metal complexes within halogen-bonded networks may lead to modulation of their properties in the solid state without the need to chemically incorporate donor or acceptor moieties on the metal complex itself. Here, we investigate the effect of anionic halogen-bonded structure formation on the organization of arene-rich bis(4′-phenyl-2,2′:6′,2″-terpyridine)nickel(II) cations, varying both the topicity and the geometry of the halogen bond donor in a heteromeric three-component system. The X-ray structures of four cocrystals (1-4), [Ni(terpy-ph)][(1,2-DITFB)(I)] (1), [Ni(terpy-ph)][(1,3-DITFB)(I)] (2), [Ni(terpy-ph)][(1,4 DITFB)(I)](I)·9HO (3), and [Ni(terpy-ph)][(1,3,5-TITFB)(HO)(I)]·2HO (4), as well as the iodide salt of the parent complex [Ni(terpy-ph)]I·4HO are reported along with characterization to assess bulk sample and phase purity. Within assemblies of complex cations, we observe the ubiquitous aryl embrace motif often seen in the crystal packing of such terpyridine complexes; however, these assemblies are separated from one another by a variety of halogen-bonded structures, including discrete supramolecular complexes, 1D chains, pseudo-2D sheets, and unusual racemic double helices. The results herein demonstrate how typical crystal packing motifs of metal terpy-ph complexes can be altered and disrupted through their incorporation into halogen-bonded heteromeric three-component systems.

Crystal Structure of a New Ordered form of Ammonium Hydrogen Succinate NH4HC4H4O4

Triclinic ammonium hydrogen succinate compound (space group $$P\stackrel{-}{1}$$) is known to present very short O–H⋅⋅⋅O hydrogen bonds in association with a second-order phase transition around 170 K. Whatever the temperature, its crystal structure is characterized by a statistical distribution of the hydrogen atom belonging to the hydrogen succinate molecule on two crystallographic sites, leading to a disordered structure. In this study, we report on the crystal structure of a new ordered structural form of the title compound NH4HC4H4O4, determined by single-crystal X-ray diffraction at room temperature. This new ordered form crystallizes in the triclinic space group $$P\stackrel{-}{1}$$ with refined cell parameters: a = 6.4868(16) A, b = 7.4313(17) A, c = 7.4339(17) A, α = 112.058(8)°, β = 96.477(9)°, γ = 109.026(8)° and V = 302.45(12) A3. Hydrogen succinate molecules are in trans conformation in the ordered form and in gauche conformation in the disordered one. It leads to different molecular assemblies of the ammonium cations and hydrogen succinate anions, and consequently, to different hydrogen bond networks. The crystal structure stability of this new ordered structural form is discussed and compared to that of the disordered form.

Electrochemical recognition of nitrophenol isomers by assembly of pillar[5]arenes mutifilms

The rational design of electrochemical methods for isomer recognition is a focus of research in the molecular recognition and separation fields. In this work, a novel, rapid, and convenient electrochemical approach for recognition of nitrophenol isomers was constructed based on the alternating layer-by-layer (LbL) assembly of water-soluble cationic and anionic pillar [5]arene on a carboxylic graphene (C-Gra) modified glass carbon electrode. The electrochemical recognition of nitrophenol isomers was investigated by differential pulse voltammetry (DPV). The electrochemical results reveal that both the peak currents of m-nitrophenol (m-NP) and p-nitrophenol (p-NP) increased with the increasing of the layer number of the assembled pillar [5]arene, whereas the peak current of o-nitrophenol (o-NP) decreased with the increased layers, which demonstrated an efficient route for discriminating the nitrophenol isomers. The molecular recognition mechanism was studied by 1H NMR spectra, which indicated that the m-NP and p-NP can be included in the cavity of the pillar [5]arene host. However, the o-NP could not enter into the host of pillar [5]arene, which was ascribed to the formation of intramolecular hydrogen bond of o-NP. The LbL assembly modified GCE was used for detecting p-NP and m-NP. A low detection limit of 0.33 μM (S/N = 3) and a linear response range of 1–90 μM for p-NP were obtained by using this method. And the detection limit of 0.16 μM (S/N = 3) and a linear response range of 0.5–70 μM for m-NP were obtained. This method of LbL assembly modified GCE has potential application in molecular recognition and separation.

Multivalent Metallosupramolecular Assemblies as Effective DNA Binding Agents.

We report the implementation of coordination chemistry onto the generation of new types of metallosupramolecular complexes with laterally appended cationic moieties for DNA binding in buffered aqueous media. Utilization of an N,N,O-type coordination pocket along with an octahedral zinc(II) metal ion allowed us to obtain mono- and tetranuclear complexes in both solution and solid state, as confirmed by NMR spectroscopy and single-crystal X-ray diffraction, respectively. By using isothermal titration calorimetry and gel electrophoresis, multiply charged cationic assemblies were observed to effectively bind to DNA through multivalent electrostatic interactions. Furthermore, we observed a correlation between the multivalency of the compounds employed and the effectiveness of DNA binding.

Layer-by-layer assembly of anionic-/cationic-pillar[5]arenes multilayer films as chiral interface for electrochemical recognition of tryptophan isomers

The rational design of electrochemical methods for chiral recognition is a focus of research in the detection fields of biomolecules and pharmaceuticals. In this work, a novel, rapid, and convenient electrochemical approach for recognition of tryptophan isomers (L-/D-Trp) was constructed based on the alternating layer-by-layer assembly of water-soluble cationic and anionic pillar[5]arene on a carboxylic graphene (C-Gra) modified glass carbon electrode. Differential pulse voltammetry (DPV) was employed to study the electrochemical recognition of tryptophan isomers. The results reveal that both the peak currents of L-Trp and D-Trp decreased with the increasing of the layer number of the assembled pillar[5]arene, whereas the peak current value's difference between the L-Trp and D-Trp increased with the increased layers, which demonstrated an efficient route for discriminating the L-Trp and D-Trp. The recognition mechanism was studied by 1H NMR spectra and molecular docking. The host−guest interaction is different for D- and L-Trp due to the opposite steric configurations of the Trp isomers, resulting in significantly discernible electrochemical differences in both peak currents and consequently effective chiral recognition of Trp isomers. This study is the first example that shows the construction of electrochemical chiral separation platform based on pillar[5]arene. This method shows potential applications in many fields, including separation, purification, storage of chiral molecule, drug detection and analysis.

Supramolecular cooperative interaction-induced assembly of phosphotungstate polyanions and sulfur-containing pyridine-based cations

Three crystals were assembled by means of multiple weak intermolecular cooperative supramolecular interactions of hydrogen bonding, S⋯O, C–H⋯π, and polyanion–π.