Supramolecular Clusters Research Articles

Self-Assembly and Mechanochromism Behavior of Gold(I) Supramolecular Cluster

Aurophilicity interaction has played a crucial role in the controllable self-assembly of polynuclear clusters with high nuclear structures and tunable photoluminescence properties. We proposed a multi-component synergistic self-assembly strategy for the controlled synthesis of a hexadeca-nuclei gold(I) supramolecular cluster through spontaneous ligand substitution and conformation rearrangement driven by AuI···AuI bonding interactions. In supramolecular cluster 12+·2BF4–, multi-components could be highly accurately aggregated together when thiolate-chloride/phosphine coordination exchange reactivity is partially activated by changing the stoichiometric ratio between digold(I) corners, dppmAu2Cl2, and ditopic linkers, trithiocyanuric salt. Mass spectra confirmed the stepwise self-assembly mechanism in solution, which was also supported by crystallographic data. Supramolecular cluster 12+·2BF4– displayed intense emission properties either in the solid state or in solution. Moreover, cluster 12+·2BF4– exhibited a reversible mechanochromic luminescence behavior in the crystalline state and aggregation-caused blue-shifted emission in solution. Hence, emissive gold(I) cluster with strong aurophilicity interactions has great potential value in the fluorescence imaging for 3D printing hydrogels.

Mesoionic compounds: the role of intermolecular interactions in their crystalline design

The quest for understanding crystal structures using supramolecular cluster demarcation has been applied to various uncharged compounds, and, more recently, to charged compounds. So, what would be the supramolecular behavior of mesoionic compounds?

The Medawar Prize Acceptance Speech 2022.

The Medawar Prize Acceptance Speech 2022.

Self-Assembly of Mechanoluminochromic Ladder-Shaped Gold(I) Clusters Promoted Using Cooperative Aurophilicity.

The self-assembly of mechanoluminochromic polynuclear gold(I) complexes has attracted more and more attention in the field of supramolecular gold(I) chemistry. In this work, we adopted a stepwise self-assembly strategy to precisely synthesize two polynuclear gold(I) supramolecular clusters. Through cooperative AuI···AuI and Au-N interactions, the gold(I) clusters 1+•BF4- and 24+•4BF4- with Au4 and Au16 cores, respectively, were successfully constructed. In these supramolecular clusters, (dppm)Au2Cl2 coordination motifs and trithiocyanuric linkers were stepwise assembled via sequential thiolate-chloride/phosphine coordination substitution and Au-S/Au-N coordination bond rearrangement. Two well-defined gold(I) supramolecular clusters displayed intense emission both in the solid state and in solution. Furthermore, the ladder-shaped cluster 24+•4BF4- exhibited reversible mechanochromic luminescence behavior in the solid state as well as aggregation-caused redshifted emission in solution. Upon mechanical grinding, the emission of the cluster 24+•4BF4- changed from yellow at 582 nm to red at 612 nm. The initial emission could be fully recovered by treatment with acetonitrile.

Formulation and Ex vivo Permeation Study of Tamoxifen Citrate Loaded Transfersomal Gel

Objective: The current study’s objective is to assess the transfersomal gel, administration of tamoxifen citrate transdermally for DEPARTMENT OF Expenditure (DOE) Approach. Materials and Methods: Supramolecular clusters with extreme flexibility, known as transferosomes can penetrate untouched animal skin. The formulations were designed by Box-Behnken design (BBD). The ex-vivo skin permeation study of tamoxifen citrate-loaded transferosomal gel was compared with commercial gel and blank drug solution. A total of 100 mg of the maximal drug release (94.32%) from the tamoxifen citrate optimized transferosome formulation demonstrated excellent results. Conclusion: According to this study, the comparatively stable transferosomes represent a promising long-term administration strategy for tamoxifen citrate. According to this study, transdermal drug delivery of skin cancer could be treated by employing transferosomes containing the tamoxifen citrate.

Regulated Adaptive Self-Assembly of Cu3I3 Supramolecular Clusters and their Photocatalytic Properties

Regulated Adaptive Self-Assembly of Cu₃I₃ Supramolecular Clusters and their Photocatalytic Properties

Supramolecular Structure of Phenyl Derivatives of Butanol Isomers

Wide-angle X-ray scattering patterns were recorded for a series of aliphatic butanol isomers (n-, iso-, sec-, tert-butanol) and their phenyl derivatives (4-phenyl-1-butanol, 2-methyl-3-phenyl-1-propanol, 4-phenyl-2-butanol, and 2-methyl-1-phenyl-2-propanol, respectively) to determine their atomic-scale structure with particular emphasis on the formation of supramolecular clusters. In addition, molecular dynamics simulations were carried out and yielded good agreement with experimental data. The combination of experimental and theoretical results allowed clarification of the origin of the pre-peak appearing at low scattering angles for the aliphatic butanols and its absence for their phenyl counterparts. It was demonstrated that the location of the hydroxyl group in the molecule of alkyl butanol, its geometry, and rigidity determine the morphology of the supramolecular clusters, while the addition of the aromatic moiety causes more disordered organization of molecules. The phenyl group significantly decreases the number of hydrogen bonds and size of the supramolecular clusters formed via the O–H···O scheme. The lower association ability of phenyl alcohols via H-bonds is additionally attenuated by the appearance of competing π–π configurations evidenced by the structural models.

The incorporation of upper vs lower rim substituted thia- and calix[4]arene ligands into polydiacethylene polymeric bilayers for rational design of sensors to heavy metal ions

1,3-Diketone calix [4]arene (CA) and thiacalix [4]arene (TCA), with the hydrophobic substituents introduced onto lower or upper rims respectively, form mixed aggregates with 10,12-pentacosadiynoic acid (PCDA) through the thin film hydration technique. Computer simulations, showing the arrangement of TCA and CA molecules in supramolecular clusters with PCDA molecules, suggest that PCDA assemblies with both cyclophanes are a convinient basis for the coordination of metal ions. However, photopolymerization of mixed aggregates reveals more disruption of the vesicular nanostructure of polydiacetylene (PDA) when CA molecules are included compared to TCA. The incorporation of the TCA and CA ligands influences the ability of the mixed PDA-bilayers to conformational and spectral changes and provides tight coordination of Tb3+ ions and efficient sensitizing of the Tb3+-centered luminescence. The PDA-bilayers incorporated by terbium TCA complex provide more sensitive response on the series of heavy metal ions vs their CA-based analogues. The surface exposed TCA rims and carboxylate moieties of PDA provide two different binding sites for Tb3+ and heavy metal ions. Both distribution of Tb3+ and heavy metal ions between these sites and heterometallic complex formation are revealed as the factors affecting the luminescence response of PDA-TCA terbium complex in the solutions of heavy metal ions. The interplay between these factors is the reason for the different luminescence response of PDA-TCA terbium complex on Cd2+, Hg2+ and Pb2+ ions. The PDA-vesicles incorporated by terbium TCA complex exhibit easier phase separation vs the PDA vesicles themselves, which favors the extraction of Pb2+ ions.

Strength and Nature of Host-Guest Interactions in Metal-Organic Frameworks from a Quantum-Chemical Perspective.

Metal‐organic frameworks (MOFs) offer a convenient means for capturing, transporting, and releasing small molecules. Their rational design requires an in‐depth understanding of the underlying non‐covalent host‐guest interactions, and the ability to easily and rapidly pre‐screen candidate architectures in silico. In this work, we devised a recipe for computing the strength and analysing the nature of the host‐guest interactions in MOFs. By assessing a range of density functional theory methods across periodic and finite supramolecular cluster scale we find that appropriately constructed clusters readily reproduce the key interactions occurring in periodic models at a fraction of the computational cost. Host‐guest interaction energies can be reliably computed with dispersion‐corrected density functional theory methods; however, decoding their precise nature demands insights from energy decomposition schemes and quantum‐chemical tools for bonding analysis such as the quantum theory of atoms in molecules, the non‐covalent interactions index or the density overlap regions indicator.

Revealing the Molecular Mechanism of Cosolvency Based on Thermodynamic Phase Diagram, Molecular Simulation, and Spectrum Analysis: The Tolbutamide Case.

Cosolvency has been observed in many systems. To reveal the mechanism of cosolvency from the molecular level, the effects of molecular conformation, supramolecular clusters, and interactions on cosolvency were systematically investigated using tolbutamide as a model compound, through experimental exploration, spectral detection, and molecular simulation. The results show that, under the influence of intermolecular and intramolecular interactions, the dominant solute molecular conformations transform and the supramolecular clusters change in different solution systems, which then lead to the cosolvency phenomena.

Recent developments in supramolecular complexes of azabenzenes containing one to four N atoms: synthetic strategies, structures, and magnetic properties.

For the last couple of decades, azabenzene-based ligands have drawn much attention from inorganic chemists due to their ability to coordinate with different metal ions to form supramolecular clusters. These azabenzenes are weak σ donors and strong π acceptors and electron-deficient. Metallogrid complexes and non-grid oligomers are well-defined supramolecular clusters, formed by appropriate chelating ligands, and can show interesting optical, magnetic, and electronic properties. Self-assembly of [n × n] metallogrid complexes is dominated by the entropic factor while the formation of oligonuclear metal ion complexes is dominated by other effects like CFSE, electrostatic factors, ligand conformational characters, etc. Herein, the present article gives an overview of six-membered heterocyclic azine-based ligands and their potential for different metal ions to form polynuclear complexes. Moreover, their temperature-dependent magnetic properties and SCO phenomena are well described and tabulated.

The role of attractive and repulsive interactions in the stabilization of ammonium salts structures

A series of ammonium salts was used to propose a step-by-step approach to obtain the stabilization energy and contact area data of supramolecular clusters in charged molecules. A new parameter was presented to assess the cluster energy efficiency.

Preparation and application of one new supramolecular molybdenum oxygen cluster with adsorption of organic contaminants in wastewater

In this paper, one supermolecular compound, namely, p-[C20H18N2O4][Mo8O26]0.5·H2O (1) has been synthesized from 1,4-bis[4-nitrile-pyridine)-N-methylene]phenyldibromide (L1) and (NH4)6Mo7- O24·4H2O by hydrothermal method. The structure has been confirmed through single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra. The adsorption property of compound 1 has bee studied, Thus it’s much important to enrich the types of chemicals.

Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes.

Nuclear magnetic resonance (NMR) spectroscopy of paramagnetic molecules provides detailed information about their molecular and electron-spin structure. The paramagnetic NMR spectrum is a very rich source of information about the hyperfine interaction between the atomic nuclei and the unpaired electron density. The Fermi-contact contribution to ligand hyperfine NMR shifts is particularly informative about the nature of the metal–ligand bonding and the structural arrangements of the ligands coordinated to the metal center. In this account, we provide a detailed experimental and theoretical NMR study of compounds of Cr(III) and Cu(II) coordinated with substituted acetylacetonate (acac) ligands in the solid state. For the first time, we report the experimental observation of extremely paramagnetically deshielded 13C NMR resonances for these compounds in the range of 900–1200 ppm. We demonstrate an excellent agreement between the experimental NMR shifts and those calculated using relativistic density-functional theory. Crystal packing is shown to significantly influence the NMR shifts in the solid state, as demonstrated by theoretical calculations of various supramolecular clusters. The resonances are assigned to individual atoms in octahedral Cr(acac)3 and square-planar Cu(acac)2 compounds and interpreted by different electron configurations and magnetizations at the central metal atoms resulting in different spin delocalizations and polarizations of the ligand atoms. Further, effects of substituents on the 13C NMR resonance of the ipso carbon atom reaching almost 700 ppm for Cr(acac)3 compounds are interpreted based on the analysis of Fermi-contact hyperfine contributions.

Energetic and structural features of SARS-CoV-2 N-protein co-assemblies with nucleic acids

SummaryNucleocapsid (N) protein of the SARS-CoV-2 virus packages the viral genome into well-defined ribonucleoprotein particles, but the molecular pathway is still unclear. N-protein is dimeric and consists of two folded domains with nucleic acid (NA) binding sites, surrounded by intrinsically disordered regions that promote liquid-liquid phase separation. Here, we use biophysical tools to study N-protein interactions with oligonucleotides of different lengths, examining the size, composition, secondary structure, and energetics of the resulting states. We observe the formation of supramolecular clusters or nuclei preceding growth into phase-separated droplets. Short hexanucleotide NA forms compact 2:2 N-protein/NA complexes with reduced disorder. Longer oligonucleotides expose additional N-protein interactions and multi-valent protein-NA interactions, which generate higher-order mixed oligomers and simultaneously promote growth of droplets. Phase separation is accompanied by a significant change in protein secondary structure, different from that caused by initial NA binding, which may contribute to the assembly of ribonucleoprotein particles within macromolecular condensates.

In Situ Capture of a Ternary Supramolecular Cluster in a 58-Nuclei Silver Supertetrahedron

Although inorganic anion templates are highly appreciated in the synthesis of nanosized silver clusters, supramolecular clusters used as templates to mold silver nanoclusters remain as-yet-unknown ...

Is a Dissociation Process Underlying the Molecular Origin of the Debye Process in Monohydroxy Alcohols?

Herein, we investigated the molecular dynamics as well as intramolecular interactions in two primary monohydroxy alcohols (MA), 2-ethyl-1-hexanol (2EHOH) and n-butanol (nBOH), by means of broad-band dielectric (BDS) and Fourier transform infrared (FTIR) spectroscopy. The modeling data obtained from dielectric studies within the Rubinstein approach [Macromolecules2013, 46, 7525−7541] originally developed to describe the dynamical properties of self-assembling macromolecules allowed us to calculate the energy barrier (Ea) of dissociation from the temperature dependences of relaxation times of Debye and structural processes. We found Ea ∼ 19.4 ± 0.8 and 5.3 ± 0.4 kJ/mol for the former and latter systems, respectively. On the other hand, FTIR data analyzed within the van’t Hoff relationship yielded the energy barriers for dissociation Ea ∼ 20.3 ± 2.1 and 12.4 ± 1.6 kJ/mol for 2EHOH and nBOH, respectively. Hence, there was almost a perfect agreement between the values of Ea estimated from dielectric and FTIR studies for the 2EHOH, while some notable discrepancy was noted for the second alcohol. A quite significant difference in the activation barrier of dissociation indicates that there are probably supramolecular clusters of varying geometry or a ring-chain-like equilibrium is strongly affected in both alcohols. Nevertheless, our analysis showed that the association/dissociation processes undergoing within nanoassociates are one of the main factors underlying the molecular origin of the Debye process, supporting the transient chain model.

Supra-Molecular Assemblies of ORAI1 at Rest Precede Local Accumulation into Puncta after Activation.

The Ca2+ selective channel ORAI1 and endoplasmic reticulum (ER)-resident STIM proteins form the core of the channel complex mediating store operated Ca2+ entry (SOCE). Using liquid phase electron microscopy (LPEM), the distribution of ORAI1 proteins was examined at rest and after SOCE-activation at nanoscale resolution. The analysis of over seven hundred thousand ORAI1 positions revealed a number of ORAI1 channels had formed STIM-independent distinct supra-molecular clusters. Upon SOCE activation and in the presence of STIM proteins, a fraction of ORAI1 assembled in micron-sized two-dimensional structures, such as the known puncta at the ER plasma membrane contact zones, but also in divergent structures such as strands, and ring-like shapes. Our results thus question the hypothesis that stochastically migrating single ORAI1 channels are trapped at regions containing activated STIM, and we propose instead that supra-molecular ORAI1 clusters fulfill an amplifying function for creating dense ORAI1 accumulations upon SOCE-activation.

Influence of molecular geometry on the formation, architecture and dynamics of H-bonded supramolecular associates in 1-phenyl alcohols

Combination of calorimetric, dielectric, infrared, diffraction studies and quantum DFT computations was used to analyze the impact of the molecular architecture of a set of four 1-phenyl alcohols (1-phenylethanol, 1-phenyl-1-propanol, 1-phenyl-1-butanol and 2-methyl-1-phenyl-1-propanol) on their glass transition temperature, molecular dynamics, relaxation processes, hydrogen-bonding pattern and intermolecular association. We showed that all these alcohols form H-bonded supramolecular nanoassociates even at room temperature, despite containing a steric hindrance in the form of the phenyl ring in the most disfavored position. However, the concentration and the size of the H-bonded structures as well as the mutual arrangement of molecules in these clusters are tremendously affected by the molecular architecture. In linear-shaped 1-phenyl alcohols, i.e., 1-phenylethanol, 1-phenyl-1-propanol, 1-phenyl-1-butanol, the intermolecular O-H···O bonds organize themselves into chain-like patterns. Moreover, these alcohols are characterized by similar strength of intermolecular H bonds at each temperature and similar glass transition temperature. In turn, the globular molecular shape of 2-methyl-1-phenyl-1-propanol leads to a weakening of H bonds in this system, an increase in the glass transition temperature and the formation of supramolecular clusters in which O-H···O connections imply ring-like organization of molecules. Finally, these studies clearly show that unlike the glass transition temperature, the molecular dynamics of the 1-phenyl alcohols in the liquid state is not only affected by the molecular architecture and hydrogen bond strength but also by the morphology of the associates composed of H-linked molecules.

Heterogeneous Supramolecular Catalysis through Immobilization of Anionic M4L6 Assemblies on Cationic Polymers.

Although most of the currently developed supramolecular catalysts that emulate enzymatic reactivity with unique selectivity and activity through specific host-guest interactions work under homogeneous conditions, enzymes in nature can operate under heterogeneous conditions as membrane-bound enzymes. In order to develop such a heterogeneous system, an immobilized chiral supramolecular cluster Ga416 (2) was introduced into cross-linked polymers with cationic functionalities. These heterogeneous supramolecular catalysts were used in aza-Prins and aza-Cope reactions and successfully applied to continuous-flow reactions. They showed high durability and maintained high turnovers for long periods of time. In sharp contrast to the majority of examples of heterogenized homogeneous catalysts, the newly developed catalysts showed enhanced activity and robustness compared to those exhibited by the corresponding soluble cluster catalyst. An enantioenriched cluster was also immobilized to enable asymmetric catalysis, and activity and enantioselectivity of the supported chiral catalyst were maintained during recovery and reuse experiments and under a continuous-flow process. Significantly, the structure of the ammonium cations in the polymers affected stability, reactivity, and enantioselectivity, which is consistent with the hypothesis that the cationic moieties in the polymer support interact with cluster as an exohedral protecting shell, thereby influencing their catalytic performance.