Hydrophobic supramolecular complexes of various cations with 18-crown-6 as the ligand and N-methoxy-picramide as the anion pair in a water/methylene chloride two-phase system: complexes with α-amino acids,their characteristics and conditions for formation

α-Amino acids (arginine, valine, glycine, isoleucine, alanine, leucine, and phenylalanine), as amphionic species, were extracted from water into methylene chloride as neutral, hydrophobic, red supramolecular complexes of the type (CE-AmAc)⁺A⁻ where CE is 18-crown-6, AmAc is RCH(NH₃)⁺ COOH, and A⁻ is the N-methoxy-2,4,6-trinitroanilinium anion, where the latter gives rise to the red colour of the complexes (λ_max = 462 nm). The extraction constants (K_exs) of the α-amino acids from water to methylene chloride as supramolecular complexes were determined in relationship to the aqueous ionic strength (I).     

Solvent-Controlled Self-Assembled Oligopyrrolic Receptor

We report a fully organic pyridine-tetrapyrrolic U-shaped acyclic receptor 10, which prefers a supramolecular pseudo-macrocyclic dimeric structure (10)₂ in a less polar, non-coordinating solvent (e.g., CHCl₃). Conversely, when it is crystalized from a polar, coordinating solvent (e.g., N,N-dimethylformamide, DMF), it exhibited an infinite supramolecular one-dimensional (1D) “zig-zag” polymeric chain, as inferred from the single-crystal X-ray structures. This supramolecular system acts as a potential receptor for strong acids, e.g., p-toluenesulfonic acid (PTSA), methane sulfonic acid (MSA), H₂SO₄, HNO₃, and HCl, with a prominent colorimetric response from pale yellow to deep red. The receptor can easily be recovered from the organic solution of the host–guest complex by simple aqueous washing. It was observed that relatively stronger acids with pK_a < −1.92 in water were able to interact with the receptor, as inferred from ¹H NMR titration in tetrahydrofuran-d₈ (THF-d₈) and ultraviolet–visible (UV–vis) spectroscopic titrations in anhydrous THF at 298 K. Therefore, this new dynamic supramolecular receptor system may have potentiality in materials science research.     

Self-healing and shape memory functions exhibited by supramolecular liquid-crystalline networks formed by combination of hydrogen bonding interactions and coordination bonding

We here report a new approach to develop self-healing shape memory supramolecular liquid-crystalline (LC) networks through self-assembly of molecular building blocks via combination of hydrogen bonding and coordination bonding. We have designed and synthesized supramolecular LC polymers and networks based on the complexation of a forklike mesogenic ligand with Ag⁺ ions and carboxylic acids. Unidirectionally aligned fibers and free-standing films forming layered LC nanostructures have been obtained for the supramolecular LC networks. We have found that hybrid supramolecular LC networks formed through metal–ligand interactions and hydrogen bonding exhibit both self-healing properties and shape memory functions, while hydrogen-bonded LC networks only show self-healing properties. The combination of hydrogen bonds and metal–ligand interactions allows the tuning of intermolecular interactions and self-assembled structures, leading to the formation of the dynamic supramolecular LC materials. The new material design presented here has potential for the development of smart LC materials and functional LC membranes with tunable responsiveness.

New supramolecular hybrid liquid-crystalline networks exhibiting self-healing and shape memory properties are developed by self-assembly of small components through hydrogen bonding interactions and coordination bonding.     

Engineering a cationic supramolecular charge switch for facile amino acids enantiodiscrimination based on extended-gate field effect transistors

Chiral recognition of essential amino acids (EAAs) is a huge challenge that keeps plaguing analytical scientists due to their cryptochirality and limited steric interaction sites. Inspired by the superior enantioselectivity of functional supramolecular cyclodextrins (CDs) and strong signal amplification ability of field effect transistors (FETs), this work firstly reports a cationic supramolecular charge switch for facile enantiodiscrimination of EAAs based on extended-gate organic FET (EG-OFET). The cationic phenylcarbamoylated-CD single isomer acts as a charge switch via interacting with different enantiomers and the weak stereo-differentiation intermolecular interaction signals between the cationic perphenylcarbamoylated CDs and EAAs on the EG can be strongly and rapidly amplified through an OFET. Efficient chiral differentiation of six EAAs, including phenylalanine, tryptophan, leucine, isoleucine, lysine and valine, are successfully achieved without any derivation process and the detection limit for d-phenylalanine is down to 10^?13 mol/L. We believe that this study provides a new and facile sensing perspective for natural amino acids and may afford deeper understanding of molecular chirality.     

Helical secondary structures and supramolecular tilted chirality in N-terminal aryl amino acids with diversified optical activities

Helix structures at atomic/molecular level have not been found in self-assembled peptide seque nce with less than three residues.As β-sheet supramolecular secondary structures have been discovered in solidstate amino acids,we here report the conjugation of simple N-terminal aryl protecting group could give rise to helical supramolecular secondary structures in solid-state,which determines the optical activities of the adjacent aryl groups.The carboxylic acid-involved asymmetric H-bonds in N-te rminal aryl amino acids induce the emergence of super-helical structures of amino acid residues and aryl groups.In most cases,supramolecular tilted chirality of aryl groups is opposite to that of amino acid sequences,of which handedness and helical pitch are determined by the H-bond modalities.Determining correlation between supramolecular tilted chirality of aryl segments and their chiroptical activities is firstly unveiled,which was verified by the computational results based on density functional theory.Most aryl amino acids self-assembled by nanoprecipitation method via crystallization induced self-assembly into rigid one-dimensional microstructures with ultra-high Young's modulus.This study reveals the generic existence of chiral supramolecular structure s in aggregated amino acid derivatives and gives an in-depth investigation into the structural-property relationships,which could guide the rational design and screening of chiroptical supramolecular materials.     

Benzyl isobornyl amines: a simple and practical class of NMR discriminating agents for effective chiral recognition of acids

The design and synthesis of a few simple N-benzyl derivatives of isobornyl amine is presented. The derivatives have been assessed as chiral solvating agents for effective discrimination of the signals of some acids in NMR analysis. The single crystal X-ray analysis of the salts of (R)-mandelic acid with two of the title derivatives help to understand the supramolecular interactions and assign the induced chemical shifts in ¹H NMR analysis. The title derivative is found to be suitable for quantitative determination of the enantiomeric excess of unknown enantiomeric purity as well as being efficient in resolving racemic mandelic acid.     

Association and colloid-chemical properties of humic acids in aqueous solutions

Colloid-chemical properties of humic acids in aqueous solutions have been studied as functions of their concentration, medium pH, and counterion nature. It has been established that, at pH < 4, Na-form humic acids exist in aqueous solutions as 30–120-nm aggregates. At pH > 4, the state of humic acids depends on the solution concentration. At low concentrations, they exist as individual molecules; as the concentration is increased, they associate to form supramolecular structures at 5 mg/dm³ and micelles at 8 g/dm³. An increase in the counterion charge has been shown to decrease the critical concentration of supramolecular structuring. Supramolecular structures have increased adsorbability on clay minerals and promote the manifestation of solubilizing properties of humic acids in solutions even at a concentration of 5 mg/dm³, which is three orders of magnitude lower than the critical micelle concentration (8 g/dm³).     

Supramolecular assemblies of Al3+ complexes with vitamin D3 (cholecalciferol) and phenothiazine. Encapsulation and complexation studies in β-cyclodextrin

Ternary assemblies of β-cyclodextrin with cholecalciferol (or vitamin D₃) or phenothiazine and Al³⁺ ions were studied. The stability constants of aluminium binary complexes with cholecalciferol or phenothiazine and of ternary assemblies (β-cyclodextrin, cholecalciferol or phenothiazine and Al³⁺) were determined using potentiometric titrations at 25 °C (I = 0.100 M). The ¹³C NMR spectra of the supramolecular structures in the solid state showed that ternary supramolecular structures associating β-cyclodextrin, cholecalciferol or phenothiazine and aluminium(III) ions were obtained. Finally, X-ray powder diffraction patterns showed that the ternary assemblies with phenothiazine are channel type inclusion complexes.     

Dendrimer-based hydrogen-bonded liquid crystalline complexes: Synthesis and characterization

Three generations of dendritic polyester macromolecules based on 5-hydroxyisophthalic acid were synthesized by the divergent growth approach. The characterization of dendritic fragments was performed using a combination of ¹H NMR, ¹³C NMR spectroscopy and elemental analysis. The dendritic hydrogen-bonded supramolecular liquid crystalline complexes were prepared from different generation of dendritic acids and stilbazole derivative containing pyridyl units. The polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) were used for investigation of the liquid crystalline properties of the hydrogen-bonded dendritic supramolecular complexes.     

New pincer-like receptor derived from trans-cyclopentane-1,2-diamine as a chiral shift reagent for carboxylic acids

A new pincer-like enantiopure receptor bearing two (1R,2R)-cyclopentane-1,2-diamine moieties has been synthesized and tested as a chiral shift reagent (CSR) for different carboxylic acids. This CSR is efficient for those acids bearing an aromatic group attached to Cα, especially for arylpropionic acids. A full structural study of the diastereomeric supramolecular complexes has allowed us to propose a reasonable model for the interaction.     

Effect of anions on supramolecular architecture of benzimidazole-based ionic salts

The reaction of N,N,N′,N′-tetrakis-(1H,benzimidazol-2ylmethyl) propane-1,3-diamine (L) with different inorganic acids affords salts viz., LH₄ ⁴⁺·4ClO₄ ^?·H₂O (1), LH₄ ⁴⁺·4Cl^?·2H₂O (2), LH₄ ⁴⁺·2H₂PO₄ ^?·H₇P₃O₁₂ ^2?·3H₃PO₄ (3), LH₄ ⁴⁺·4NO₃ ^? (4), and 2LH⁺·2CF₃COO^?·5H₂O (5). The X-ray crystallographic studies revealed that the proton transfer occurred from acid to the ligand. It also demonstrated that different type of hydrogen bond between protonated ligand and anions is responsible for the supramolecular framework. The colorimetric test showed color change upon the addition of acids in the solution of the ligand. The photo-physical experiments suggested the fluorescence properties of ligand in the presence of acids.     

A linear supramolecular polymer based on host-guest recognition and metal-ligand coordination

A linear main-chain supramolecular polymer was constructed in aqueous solution via γ-CD host recognition with coumarin unit as well as metalligand coordination between terpyridine unit and Zn²⁺. Besides, the self-assembly behavior and morphological property of this supramolecular polymer system were characterized by DLS and TEM experiments.     

Ion spray-tandem mass spectrometry of supramolecular coordination complexes

Double-helical [M₂L₂] ⁿ⁺, triple-helical [M₂L₃] ⁿ⁺, and toroidal [M₃L₃] ⁿ⁺ (M = Cu, Co, Fe, Ni, La, Eu, Gd, Tb, or Lu) supramolecular complexes have been fully characterized by ion spray mass spectrometry (IS-MS). The IS-MS spectra from pure acetonitrile solutions reflect the nature of the cations present in solution with conservation of the charge state and allow an efficient qualitative speciation of the compounds. The mass spectrometry results can be correlated with other powerful techniques (nuclear magnetic resonance and electronic spectroscopy) for the characterization of supramolecular complexes in solution, Structural information is obtained by collision-induced dissociation, which strongly depends on the metal ions used in the supramolecular complexes and on the various connectivities and topologies of the ligands. When the ligand contains 3,5dimethoxybenzyl groups bound to the benzimidazole rings, the partial fragmentation of the complexes is associated with a decrease of the total charge of the complexes and the appearance of the characteristic fragment at m/z 151 that corresponds to the 3,5-dimethoxybenzyl cation. A detailed analysis of the fragmentation pathways of these supramolecular complexes suggests that the metal-nitrogen coordination bonds are very strong in the gas phase.     

Helicity-driven chiral self-sorting supramolecular polymerization with Ag+: right- and left-helical aggregates

The study of chiral self-sorting is extremely important for understanding biological systems and for developing applications for the biomedical field. In this study, we attempted unprecedented chiral self-sorting supramolecular polymerization accompanying helical inversion with Ag⁺ in one enantiomeric component. Bola-type terpyridine-based ligands (R-L¹ and S-L¹) comprising R- or S-alanine analogs were synthesized. First, R-L¹ dissolved in DMSO/H₂O (1 : 1, v/v) forms right-handed helical fibers (aggregate I) via supramolecular polymerization. However, after the addition of AgNO₃ (0.2–1.1 equiv.) to the R-L¹ ligand, in particular, it was found that aggregate II with left-handed helicity is generated from the [R-L¹(AgNO₃)₂] complex through the [R-L¹Ag]⁺ complex via the dissociation of aggregate I by a multistep with an off pathway, thus demonstrating interesting self-sorting properties driven by helicity and shape discrimination. In addition, the [R-L¹(AgNO₃)₂] complex, which acted as a building block to generate aggregate III with a spherical structure, existed as a metastable product during the formation of aggregate II in the presence of 1.2–1.5 equiv. of AgNO₃. Furthermore, the AFM and CD results of two samples prepared using aggregates I and III with different volume ratios were similar to those obtained upon the addition of AgNO₃ to free R-L¹. These findings suggest that homochiral self-sorting in a mixture system occurred by the generation of aggregate II composed of the [R-L¹Ag]⁺ complex via the rearrangement of both, aggregates I and III. This is a unique example of helicity- and shape-driven chiral self-sorting supramolecular polymerization induced by Ag⁺ starting from one enantiomeric component. This research will improve understanding of homochirality in complex biological models and contribute to the development of new chiral materials and catalysts for asymmetric synthesis.

Chiral self-sorting supramolecular polymerization of bola-type terpyridine-based ligands (R-L¹ and S-L¹) comprising R- or S-alanine analogs occurred upon addition of Ag⁺ in one enantiomeric component.     

Branched supramolecular polymers formed by bifunctional cyclodextrin derivatives

Branched supramolecular polymers have been prepared from the mixture of 3-cinnamamide-α-CD (1) and 3-N^α-cinnamamidehexancarbonyl-N^?-cinnamamide-lysinamide-α-CD (3) and from the mixture of 3-cinnamamidehexanamide-α-CD (2) and 3. Compounds 1 and 2 formed a linear supramolecular polymer, whereas compound 3 having two guest moieties formed a hyperbranched supramolecular polymer. Physical properties of these supramolecular polymers were studied by viscosity measurements in aqueous solutions. When compound 3 was added to the solution of compound 2, the η_sp/C value of the mixture of 2 and 3 was found to be much higher than that of compound 2. These results indicate that compound 3 functions as a branching moiety to increase the viscosity. Supramolecular polymers consisting of compound 2 or 3 did not show the viscosity increase, whereas the mixture of 2 and 3 gave highly viscous solutions and formed fibers from the concentrated aqueous solutions. It is caused by the branching of linear supramolecular polymers with compound 3 and hydrophobic and/or hydrogen bonding interactions between supramolecular polymers.     

Discovery of phosphotyrosine-binding oligopeptides with supramolecular target selectivity

We demonstrate phage-display screening on self-assembled ligands that enables the identification of oligopeptides that selectively bind dynamic supramolecular targets over their unassembled counterparts. The concept is demonstrated through panning of a phage-display oligopeptide library against supramolecular tyrosine-phosphate ligands using 9-fluorenylmethoxycarbonyl-phenylalanine-tyrosine-phosphate (Fmoc-FpY) micellar aggregates as targets. The 14 selected peptides showed no sequence consensus but were enriched in cationic and proline residues. The lead peptide, KVYFSIPWRVPM-NH₂ (P7) was found to bind to the Fmoc-FpY ligand exclusively in its self-assembled state with K_D = 74 ± 3 μM. Circular dichroism, NMR and molecular dynamics simulations revealed that the peptide interacts with Fmoc-FpY through the KVYF terminus and this binding event disrupts the assembled structure. In absence of the target micellar aggregate, P7 was further found to dynamically alternate between multiple conformations, with a preferred hairpin-like conformation that was shown to contribute to supramolecular ligand binding. Three identified phages presented appreciable binding, and two showed to catalyze the hydrolysis of a model para-nitro phenol phosphate substrate, with P7 demonstrating conformation-dependent activity with a modest k_cat/K_M = 4 ± 0.3 × 10⁻⁴ M⁻¹ s⁻¹.

Phage-display screening on self-assembled tyrosine-phosphate ligands enables the identification of oligopeptides selective to dynamic supramolecular targets, with the lead peptide showing a preferred hairpin-like conformation and catalytic activity.     

A chiral SrSi2 (srs) superstructure constructed by a dual interaction system showing isotropic electrical conductivity

Most porous conductive frameworks are highly anisotropic in their structures thus leading to anisotropic charge transport. Here we report a supramolecular self-assembly which is constructed by intermolecular hydrogen bonding and π ···π interactions. This material features a chiral, porous, cubic framework structure with π-stacked helical columns along all of the three Cartesian coordinates. As a result, isotropic charge transport with an electrical conductivity(σ) of 2.1 × 10^–7S/cm is...     

Supramolecular Hybrids from Cyanometallate Complexes and Diblock Copolypeptide Amphiphiles in Water

The self-assembly of discrete cyanometallates has attracted significant interest due to the potential of these materials to undergo soft metallophilic interactions as well as their optical properties. Diblock copolypeptide amphiphiles have also been investigated concerning their capacity for self-assembly into morphologies such as nanostructures. The present work combined these two concepts by examining supramolecular hybrids comprising cyanometallates with diblock copolypeptide amphiphiles in aqueous solutions. Discrete cyanometallates such as [Au(CN)₂]⁻, [Ag(CN)₂]⁻, and [Pt(CN)₄]²⁻ dispersed at the molecular level in water cannot interact with each other at low concentrations. However, the results of this work demonstrate that the addition of diblock copolypeptide amphiphiles such as poly-(L-lysine)-block-(L-cysteine) (Lys_m-b-Cys_n) to solutions of these complexes induces the supramolecular assembly of the discrete cyanometallates, resulting in photoluminescence originating from multinuclear complexes with metal-metal interactions. Electron microscopy images confirmed the formation of nanostructures of several hundred nanometers in size that grew to form advanced nanoarchitectures, including those resembling the original nanostructures. This concept of combining diblock copolypeptide amphiphiles with discrete cyanometallates allows the design of flexible and functional supramolecular hybrid systems in water.     

Supramolecular adducts of mesocyclic diamines with various carboxylic acids: Charge-assisted hydrogen-bonding in molecular recognition

Aggregation of saturated mesocyclic diamine 1,4-diazacycloheptane (dach) or piperazine (pipz) and diversiform carboxylic acids with mono- or di-carboxyls yields a series of novel binary supramolecular adducts via two-point molecular recognition. All the supramolecular assemblies were obtained by solvent evaporation method from different media. X-ray single-crystal diffraction analyses reveal that these supramolecular moieties present 1D chain motif, 2D flat, corrugated sheet structures and 3D CdSO₄, pillar-layered networks through carboxylate-amide N–H⋯O, as well as its proton transfer form N⁺–H⋯O⁻, carboxyl head to tail O–H⋯O, and extended hydrogen-bonding interactions. Their compositions and structures were also confirmed by Fourier transform infrared (FT-IR) spectroscopy. Thermal stability of these binary crystalline adducts has been investigated by thermogravimetric analysis (TGA), suggesting similar thermal stabilities.     

Self-assembly of supramolecular polymers in water from tetracationic and tetraanionic monomers in water through cooperative electrostatic attraction and aromatic stacking

The cooperative electrostatic attraction and π-π stacking between tetrahedral tetrapyridinium and three tetraanionic tetraphenylethylenes led to the formation of a new series of supramolecular polymers in water.