Supramolecular Clusters Research Articles

Remalleable, Healable, and Highly Sustainable Supramolecular Polymeric Materials Combining Superhigh Strength and Ultrahigh Toughness.

To build a sustainable society, it is of significant importance but highly challenging to develop remalleable, healable, and biodegradable polymeric materials with integrated high strength and high toughness. Here, we report a superstrong and ultratough sustainable supramolecular polymeric material with a toughness of ca. 282.3 J g-1 (395.2 MJ m-3) in combination with a tensile strength as high as ca. 104.2 MPa and a Young's modulus of ca. 3.53 GPa. The toughness is even higher than that of the toughest spider silk (ca. 354 MJ m-3) ever found in the world, while the material also exhibits a superior tensile strength over most engineering plastics. This material is fabricated by topological confinement of the biodegradable linear polymer of poly(vinyl alcohol) (PVA) via the naturally occurring dendritic molecules of tannic acid (TA) based on high-density hydrogen bonds. Simply blending TA and PVA in aqueous solutions at acidic conditions leads to the formation of TA-PVA complexes as precipitates, which can be processed into dry TA-PVA composite products with desired shapes via the compression molding method. Compared to the conventional solution casting method for the fabrication of PVA-based thin films, the as-developed strategy allows large-scale production of bulk TA-PVA composites. The TA-PVA composites consist of interpenetrating three-dimensional supramolecular TA-PVA clusters. Such a structural feature, revealed by computational simulations, is crucial for the integrated superhigh strength and ultrahigh toughness of the material. The biodegradable TA-PVA composites are remalleable for multiple generations of recycling and healable after break, at room temperature, by the assistance of water to activate the reversibility of the hydrogen bonds. The TA-PVA composites show high promise as sustainable substitutes for conventional plastics because of their remalleability, healability, and biodegradability. The integrated superhigh strength and ultrahigh toughness of the TA-PVA composites ensure their high reliability and broad applicability.

Supramolecular clusters clarification in ethanol-water mixture by using fluorescence spectroscopy and 2D correlation analysis

Due to the importance of ethanol-water solutions in many fields the different supramolecular clusters involved in this binary system is studied in detail by using fluorescence spectroscopy, at different concentration and incubation time after mixing. Two-dimensional (2D) correlation analysis is performed on the concentration-dependent mixtures (10–100%) at each incubation time, which find that the correlation intensity of emission peak at 330 nm for (H2O)m(EtOH)n not only related to the concentration but also gradually increase with the incubation time. Such results indicate that the cluster of (H2O)m(EtOH)n is the most stable one because it tends to be formed with longer incubation time. In addition, the correlation results indicate that at low concentration range of 10–45%, the dominated cluster is (H2O)m(EtOH) corresponding to a peak at 373 nm; while at high concentration range of 80–100%, the main cluster is (H2O)(EtOH)n corresponding to an emission peak at 308 nm; however, the most stable cluster of (H2O)m(EtOH)n, corresponding to the peak at 330 nm, not only predominate at the concentration range of 50–75% but also exist in all mixture at longer incubation time. Therefore, the present study provides a new approach to clarify the different supramolecular clusters in ethanol-water mixtures, which would be applied to other binary solution system.

Darren Johnson.

"The best advice I have ever been given is in two parts: 1) while it is important in life to learn how to connect dots, you have to collect dots first, and 2) don't forget to give yourself time to think …" Find out more about Darren Johnson in his Author Profile.

Halogen Bonding Provides Heterooctameric Supramolecular Aggregation of Diaryliodonium Thiocyanate

The crystal structure of the newly synthesized 4-methoxyphenyl(phenyl)iodonium thiocyanate, [PhI(4-C6H4OMe)](SCN), represents the first example of 16-membered cyclic heterooctamer formed by halogen bonding between the iodonium cation and SCN−. Results of density functional theory (DFT) calculations followed by the topological analysis of the electron density distribution within the framework of the quantum theory of atoms in molecules (QTAIM) method at the ωB97XD/DZP-DKH level of theory reveal that energies of attractive intermolecular noncovalent interactions I···S and I···N (responsible for the formation of heterooctameric supramolecular clusters {PhI(4-C6H4OMe)}4·{SCN}4 in the solid state structure of [PhI(4-C6H4OMe)](SCN)) vary from 0.9 to 8.5 kcal/mol.

Super-resolution Imaging of the T cell Central Supramolecular Signaling Cluster Using Stimulated Emission Depletion Microscopy.

Supramolecular signaling assemblies are of interest for their unique signaling properties. A µm scale signaling assembly, the central supramolecular signaling cluster (cSMAC), forms at the center interface of T cells activated by antigen presenting cells (APC). The adaptor protein linker for activation of T cells (LAT) is a key cSMAC component. The cSMAC has widely been studied using total internal reflection fluorescence microscopy of CD4+ T cells activated by planar APC substitutes. Here we provide a protocol to image the cSMAC in its cellular context at the interface between a T cell and an APC. Super resolution stimulated emission depletion microscopy (STED) was utilized to determine the localization of LAT, that of its active, phosphorylated form and its entire pool. Agonist peptide-loaded APCs were incubated with TCR transgenic CD4+ T cells for 4.5 min before fixation and antibody staining. Fixed cell couples were imaged using a 100x 1.4 NA objective on a Leica SP8 AOBS confocal laser scanning microscope. LAT clustered in multiple supramolecular complexes and their number and size distributions were determined. Using this protocol, cSMAC properties in its cellular context at the interface between a T cell and an APC could be quantified.

Substituent effects on the crystallization mechanisms of 7-chloro-4-substituted-quinolines

The crystallization mechanisms of a series of fourteen 7-chloro-4-substituted-quinolines were proposed based on a retrocrystallization approach using the supramolecular cluster as demarcation.

Energetically significant unconventional O[sbnd]H⋯π contacts involving discrete guest (H2O)8 clusters in a fumarato bridged polymeric supramolecular host of Ni(II) phenanthroline: Antiproliferative evaluation and theoretical studies

A new coordination polymer of nickel(II) involving bridging fumarato viz. catena[μ-fumarato(1,10-phenanthroline monohydrate(diaqua))nickel(II)trihydrate], {[Ni(μ-fum)(phen)(H2O)2].3H2O}n (1) (where, fum = fumarate, phen = 1,10-phenanthroline monohydrate) has been synthesized in purely aqueous medium at room temperature. The crystal structure of the polymer has been determined by single crystal X-ray Diffraction analysis. The polymer has been characterised by FT-IR, electronic spectroscopy, thermal and elemental analysis. The zig-zag polymeric chain of 1 self assembles into 2D supramolecular network architecture via reciprocal π-π stacking interactions. The lattice water molecules are involved in the formation of unique supramolecular octameric linear water clusters involving alternate trimeric rings that stabilizes the 2D network architecture. The crystal structure of the polymer also reveals the self-assembled enclathration of (H2O)8 cluster into polymeric Ni(II) host involving fum ligands that brings rigidity to the structure. Theoretical calculations have been performed to analyse the non-covalent interactions observed in the solid-state structure of 1. In particular, we have analysed the π–π stacking interactions between the phen ligands and also the energetically significant unconventional OH⋯π interaction involving the π-system of fum. For the latter, we have investigated the ability of the double bond of fum (coordinated to Ni) to establish OH⋯π interaction with water in comparison to fum acid and simple ethene. Finally, the polymer has been investigated for potential anticancer activities considering cell cytotoxicity, apoptosis and molecular docking as a major parameters against Dalton’s lymphoma (DL) malignant cancer cell line and the results were compared with cisplatin (reference drug) under the same experimental conditions. DNA interaction and fragmentations have been investigated for compound 1 and pharmacophore features establish structure activity relationship (SAR).

Transient protein accumulation at the center of the T cell antigen-presenting cell interface drives efficient IL-2 secretion.

Supramolecular signaling assemblies are of interest for their unique signaling properties. A µm scale signaling assembly, the central supramolecular signaling cluster (cSMAC), forms at the center of the interface of T cells activated by antigen-presenting cells. We have determined that it is composed of multiple complexes of a supramolecular volume of up to 0.5 µm3 and associated with extensive membrane undulations. To determine cSMAC function, we have systematically manipulated the localization of three adaptor proteins, LAT, SLP-76, and Grb2. cSMAC localization varied between the adaptors and was diminished upon blockade of the costimulatory receptor CD28 and deficiency of the signal amplifying kinase Itk. Reconstitution of cSMAC localization restored IL-2 secretion which is a key T cell effector function as dependent on reconstitution dynamics. Our data suggest that the cSMAC enhances early signaling by facilitating signaling interactions and attenuates signaling thereafter through sequestration of a more limited set of signaling intermediates.

Deciphering the hydrogen-bonding scheme in the crystal structure of triphenylmethanol: a tribute to George Ferguson and co-workers.

The crystal structure of triphenylmethanol, C19H16O, has been redetermined using data collected at 295 and 153 K, and is compared to the model published by Ferguson et al. over 25 years ago [Ferguson et al. (1992). Acta Cryst. C48, 1272-1275] and that published by Serrano-González et al., using neutron and X-ray diffraction data [Serrano-González et al. (1999). J. Phys. Chem. B, 103, 6215-6223]. As predicted by these authors, the hydroxy groups are involved in weak intermolecular hydrogen bonds in the crystal, forming tetrahedral tetramers based on the two independent molecules in the asymmetric unit, one of which is placed on the threefold symmetry axis of the R-3 space group. However, the reliable determination of the hydroxy H-atom positions is difficult to achieve, for two reasons. Firstly, a positional disorder affects the full asymmetric unit, which is split over two sets of positions, with occupancy factors of ca 0.74 and 0.26. Secondly, all hydroxy H atoms are further disordered, either by symmetry, or through a positional disorder in the case of parts placed in general positions. We show that the correct description of the hydrogen-bonding scheme is possible only if diffraction data are collected at low temperature. The prochiral character of the hydrogen-bonded tetrameric supramolecular clusters leads to enantiomorphic three-dimensional graphs in each tetramer. The crystal is thus a racemic mixture of supS and supR motifs, consistent with the centrosymmetric nature of the R-3 space group.

In-situ N/S Co-doping three-dimensional succulent-like hierarchical carbon assisted by supramolecular polymerization for high-performance supercapacitors

Three-dimensional N/S co-doped succulent-like hierarchical carbon (3D NS-SHC) is synthesized by carbonization of a supramolecular cluster. In this supramolecular process, potassium citrate can act as a reliable carbon source, while the thiourea as a N/S source and then, two molecules gradually tend to generate a giant “all-in-one” precursor via hydrogen bonding verified by Independent Gradient Model (IGM) calculation. TEM and SEM images show the N/S co-doped carbon holds a novel 3D succulent-like hierarchical structure. For NS-SHC-8:8 sample, element mapping images display the uniform N/S atoms distribution. These distinct features can be related to the supramolecular polymerization which promotes in-situ N/S co-doping homogenously and conduces to build 3D structure. Typically, NS-SHC-8:8 electrode exhibits prominent specific capacitance (258.5 F g−1 at 0.5 A g−1) and excellent cycle stability (94.4% after 20000 cycles) in three-electrode system. Furthermore, an assembled quasi-solid state symmetric supercapacitor delivers good energy density (10.2 Wh kg−1 at 250 W kg−1) and steady cycle endurance (85.1% after 10000 cycles). These eximious behaviors of NS-SHC-8:8 are mainly attributed to (1) the uniform N/S atoms distribution and their synergistic effect, which brings extra Faradaic reaction to higher specific capacitance, (2) the charming 3D succulent-like hierarchical structure, which serves as a multifunctional reservoir that can accommodate the ion/charge and facilitate their migration to further promote the electrochemical performance. Above mentions suggest that this uniformly heteroatom-modified carbon material produced by supramolecular technique is promising for high-performance energy storage devices.

Supramolecular self-assembly and thermodynamic properties of 5-aryl-1-(1,1-dimethylethyl)-1H-pyrazoles in the crystalline state

A series of seven 5-aryl-1-(1,1-dimethylethyl)-3-trifluoromethyl-1H-pyrazoles [in which aryl: C6H5 (1); C6H4-4-F (2); C6H4-4-Cl (3); C6H4-4-Br (4); C6H4-4-I (5); C6H4-4-CH3 (6), C6H4-4-OCH3 (7)] and 5-aryl-1-(1,1-dimethylethyl)-1H-pyrazole [C6H4-4-NO2 (8)] was studied at the molecular and supramolecular level. X-ray diffraction, thermal analysis, sublimation enthalpy data, NMR spectroscopy, and DFT calculations were used in this systematic study. The supramolecular cluster was used as demarcation and furnished energetic and contact area data of each compound, which allowed proposals of crystallization mechanisms. Two different mechanisms were observed: (i) compounds 1–4 had 2 stages, where initially the monomers formed a 2-D block, followed by the formation of the 3-D block; (ii) compounds 5–8 also had 2 stages, where initially the monomers formed a 1-D block, followed by formation of the 3-D block. The packing observed in the crystal was corroborated by data from 1H NMR experiments. The types of interactions observed were evaluated using Hirshfeld surface and QTAIM analysis and showed slight differences in both methods. Lastly, energetic and topologic data obtained from the clusters were correlated with crystal properties such as crystal packing efficiency, sphericity, and sublimation enthalpy and presented good trends between data.

Separation of 2-Bromobutane, 2-Chlorobutane, 2-Chloropentane, and 2-Butanol Enantiomers Using a Stationary Phase Based on a Supramolecular Uracil Structure

We proposed a new chiral stationary phase based on a supramolecular uracil structure with induced chirality. According to the Kondepudi effect, mechanical stirring leads to the formation of a supramolecular structure layer on the surface of an adsorbent with a predominance of one of types of chiral supramolecular clusters. The obtained stationary phase was used for the gas-chromatographic separation of enantiomers of 2-bromobutane, 2-chlorobutane, 2-chloropentane, and 2-butanol. The effectiveness of a 1-m column packed with an inert stationary phase modified with uracil is 200–400 theoretical plates. The enantiomers of 2-bromobutane and 2-chlorobutane were completely separated using the proposed stationary phase in 210 and 180 s, respectively, at 45°C. The enantiomers of 2-chloropentane were separated at 60 and 65°C in 170 and 160 s, respectively. The enantiomers of 2-butanol were partially separated at 100°C. The enantioselectivity of the proposed stationary phase is probably associated with the adsorption of one enantiomer outside the cavity of the supramolecular structure and the other enantiomer inside it.

Design of Supramolecular Cluster Compounds of Copper Subgroup Metals Based on Polydentate Phosphine Ligands

Principles and examples of assembling heteroleptic supramolecular cluster compounds of copper subgroup metals based on polydentate phosphine ligands of various topologies are considered. The choice of an organic linker between phosphorus atoms allows one to control the formation of three-dimensional aggregates with a regular architecture, whereas the choice of alkynyl ligands determines their luminescent properties.

SWINGER: a clustering algorithm for concurrent coupling of atomistic and supramolecular liquids.

In this contribution, we review recent developments and applications of a dynamic clustering algorithm SWINGER tailored for the multiscale molecular simulations of biomolecular systems. The algorithm on-the-fly redistributes solvent molecules among supramolecular clusters. In particular, we focus on its applications in combination with the adaptive resolution scheme, which concurrently couples atomistic and coarse-grained molecular representations. We showcase the versatility of our multiscale approach on a few applications to biomolecular systems coupling atomistic and supramolecular water models such as the well-established MARTINI and dissipative particle dynamics models and provide an outlook for future work.

Supramolecular azasugar clusters based on an amphiphilic fatty-acid-deoxynojirimycin derivative as multivalent glycosidase inhibitors.

A novel supramolecular multivalent glycosidase inhibitor was constructed based on the amphiphilic deoxynojirimycin derivative FA-DNJ. FA-DNJ self-assembled into spherical assemblies with the diameters between 103 nm and 137 nm under different pH values (pH 2-7) and showed a potent glycosidase effect against α-mannosidase with a Ki value of 0.11 μM, an effect that increased approximately 330-fold compared with that of miglitol. In addition, FA-DNJ exhibited a hypoglycaemic effect in mice.

Supramolecular Metallopolymers: From Linear Materials to Infinite Networks.

The fields of coordination polymers (CPs) and supramolecular metallopolymers (SMPs) have been extensively studied for decades. Spectacular recent advances in both fields have created new compounds that lie at the interface between these two classes of organic-inorganic hybrid materials. At this interface, materials based on molecular weaving, supramolecular clusters, and metal-organic framework-polymer hybrids have emerged. This minireview provides a perspective on the intellectual emergence and connection between different supramolecular constructs and the state of the art with respect to this new materials interface.

Supramolecular Packing of a Series of N-Phenylamides and the Role of NH···O=C Interactions.

A series of seven N-phenylamides [R–C(O)NHPh, in which R: CH3, C(CH3)3, Ph, CF3, CCl3, CBr3, and H] were used as models in this study. Molecular packing and intermolecular interactions were evaluated by theoretical calculations, solution NMR, and quantum theory of atoms in molecules analyses. Crystallization mechanisms were proposed based on the energetic and topological parameters using the supramolecular cluster as demarcation. Concentration-dependent 1H NMR experiments corroborated the proposed interactions between molecules. For all compounds (except for R: H, which initially formed tetramers), layers (two-dimensional) or chains (one-dimensional) were formed in the first stage of the proposed crystallization mechanisms. The presence of strong intermolecular NH···O=C interactions promoted the first stages. The study in solution provided different values of association constant (Kass) governed by the hydrogen bond NH···O=C, showing that the stronger interactions are directly influenced by the substituent steric hindrance. A correlation between Kass(NH···O=C) from the solution and the NH···O=C interaction energy in the crystal showed a good trend.

Formation of Supramolecular Clusters at the Interface of Zeolite X Following the Adsorption of Rare-Earth Cations and Their Impact on the Macroscopic Properties of the Zeolite.

The adsorption behavior of neodymium (Nd3+ ) and yttrium (Y3+ ) cations on synthetic FAU zeolite X in its sodium form (NaX) has been investigated by means of macroscopic (adsorption isotherm determination and thermal analysis) and microscopic measurements (including solid-state NMR spectroscopy and X-ray powder diffraction). The multidisciplinary study reveals some unexpected features. Firstly, adsorption constants of cations are not correlated to their ionic radii or hydration enthalpy. The adsorption constant of Y3+ on NaX was indeed about twice that of Nd3+ , which is the opposite of what could be expected based on the size of the cations. In addition, adsorption was accompanied by partial dealumination of the zeolite framework. The extent of dealumination changed depending on the exchanged cations, with the extent being more significant on the Nd-exchanged zeolite than on the Y-exchanged one. The most interesting finding of this study, however, is the presence of supramolecular clusters composed of water, Nd3+ , residual sodium ions, and extra-framework aluminum at the interface of Nd-exchanged zeolite. The hypothesis that these host-guest complexes are responsible of the significantly different behavior exhibited by NaX towards the adsorption/desorption of Nd3+ and Y3+ has been formulated.

Insights on the Similarity of Supramolecular Structures in Organic Crystals Using Quantitative Indexes.

The quest for concepts of isostructurality in organic crystals has been long and mostly based on geometric data, even with the development of modern software. This field of study is of great interest to the pharmaceutical industry and for the prediction of crystal structures. Despite this, there is still no methodology that provides broad quantitative and comparable similarity data between two complete crystalline structures. The present study demonstrated that the similarity between two crystalline structures could be estimated from the similarity between the two “supramolecular clusters”. Quantitative indexes for similarity comparisons of crystal structures were shown using nine 5-aryl-1-(1,1-dimethylethyl)-1H-pyrazoles as a model. This proposal includes the quantitative data of a geometric parameter (ID), a contact area parameter (IC), and an energetic parameter (IG). The proposed indexes exhibited good perspective regarding the similarity data and distinct regions of similarity. The range of similarity was set at IX ≥ 0.80, 0.80 > IX > 0.60, and IX ≤ 0.60 (X = D, C, or G). Indexes with a value near 1.0 indicate systems with isostructural, isocontact, and isoenergetic behavior. The results indicated that supramolecular structures with high similarity must have high values for all three indexes (ID, IC, and IG).

Formation ofH2-rich iodine-hydrogen compounds at high pressure

We have used synchrotron x-ray and Raman spectroscopic studies combined with molecular dynamics to investigate the ${\mathrm{I}}_{2}\ensuremath{-}{\mathrm{H}}_{2}$ system at high pressure. By laser heating the mixture above 25 GPa we synthesized the molecular compound $\mathrm{HI}{({\mathrm{H}}_{2})}_{13}$, with the ${AB}_{13}$ structure type and unusually high volumetric hydrogen content. The isolation of HI molecules by ${({\mathrm{H}}_{2})}_{13}$ supramolecular clusters stabilizes the compound over a remarkable pressure range from 9 to at least 130 GPa. At lower pressures and 300 K another compound, hydrogen diiodane ${\mathrm{H}}_{2}{(\mathrm{HI})}_{2}$, spontaneously forms, being stable up to 12.5 GPa.