Search results for "Supramolecular"
showing 10 items of 830 documents
Bamboo-like Chained Cavities and Other Halogen-Bonded Complexes from Tetrahaloethynyl Cavitands with Simple Ditopic Halogen Bond Acceptors
2018
Halogen bonding provides a useful complement to hydrogen bonding and metal-coordination as a tool for organizing supramolecular systems. Resorcinarenes, tetrameric bowl-shaped cavitands, have been previously shown to function as efficient scaffolds for generating dimeric capsules in both solution and solid-phase, and complicated one-, two-, and three-dimensional frameworks in the solid phase. Tetrahaloethynyl resorcinarenes (bromide and iodide) position the halogen atoms in a very promising “crown-like” orientation for acting as organizing halogen-bond donors to help build capsules and higher-order networks. Symmetric divalent halogen bond acceptors including bipyridines, 1,4-dioxane, and 1…
Template-Free Supracolloidal Self-Assembly of Atomically Precise Gold Nanoclusters : From 2D Colloidal Crystals to Spherical Capsids
2016
We report supracolloidal self-assembly of atomically precise and strictly monodisperse gold nanoclusters involving p-mercaptobenzoic acid ligands (Au102-pMBA44) under aqueous conditions into hexagonally packed monolayer-thick two-dimensional facetted colloidal crystals (thickness 2.7 nm) and their bending to closed shells leading to spherical capsids (d ca. 200 nm), as controlled by solvent conditions. The 2D colloidal assembly is driven in template-free manner by the spontaneous patchiness of the pMBA ligands around the Au102-pMBA44 nanoclusters preferably towards equatorial plane, thus promoting inter-nanocluster hydrogen bonds and high packing to planar sheets. More generally, the findin…
Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods.
2018
The self-assembled structures of atomically precise, ligand-protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs) is presented. Unlike highly sophisticated DNA nanotechnology, this strategically simple hydrogen bonding-directed self-assembly of nanoclusters leads to octahedral nanocrystals encapsulating GNRs. Specifically, the p-mercaptobenzoic acid (pMBA)-protected atomically precise silver nanocluster, Na4 [Ag44 (pMBA)30 ], and pMBA-functionalized GNRs were used. High-resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver …
Experiences with applications of macromolecular tools in supramolecular crystallography
2014
Supramolecular structures, with ever increasing size ranging from a few up to tens of nanometres, represent an intermediate stage between small molecules and biological macromolecules. Many crystal structures of these large supramolecular assemblies have been solved using dual space algorithms. However, supramolecular assemblies with a capsular shape present a particular challenge for crystallography, especially when they are chiral and composed of only light atoms. In this paper, we show that the application of “routine” macromolecular tools may be of great help in solving the crystal structures of supramolecular assemblies that are otherwise refractory to the routine methods of small mole…
Programmable assembly of peptide amphiphile via noncovalent-to-covalent bond conversion
2017
Controlling the number of monomers in a supramolecular polymer has been a great challenge in programmable self-assembly of organic molecules. One approach has been to make use of frustrated growth of the supramolecular assembly by tuning the balance of attractive and repulsive intermolecular forces. We report here on the use of covalent bond formation among monomers, compensating for intermolecular electrostatic repulsion, as a mechanism to control the length of a supramolecular nanofiber formed by self-assembly of peptide amphiphiles. Circular dichroism spectroscopy in combination with dynamic light scattering, size-exclusion chromatography, and transmittance electron microscope analyses r…
Self-assembly of catalytically-active supramolecular coordination compounds within metal-organic frameworks
2019
[EN] Supramolecular coordination compounds (SCCs) represent the power of coordination chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesized in solution, with isolated fully coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-organic frameworks (MOFs) show unique features to act as chemical nanoreactors for the in situ synthesis and stabilization of otherwise not accessible functional species. Here, we present the self-assembly of Pd-II SCCs within the confined space of a pre-formed MOF (SCCs@MOF) and its post-assembly metalation to give a Pd-II-Au-III supra molecular assembly, c…
Unzipping Nucleoside Channels by Means of Alcohol Disassembly
2013
Gold nanoparticles capped with simple adenosine derivatives can form colloidal aggregates in nonpolar solvents. Theoretical calculations indicate the formation of organic channels by the supramolecular assembly of the nanoparticles by means of hydrogen bonds between the adenine moieties. The aggregates were only negligibly sensitive to nPrOH, iPrOH, and tBuOH, whereas some showed a similar response to MeOH and EtOH, and others showed high selectivity toward MeOH. DNA nucleoside derivatives (1-(2-deoxy-β-D-ribofuranosyl)-5-methyluracil and 2′,3′-O-isopropylideneadenosine) as well as thymine and other aromatic compounds such as pyrene derivatives (pyrene, 1-chloropyrene, 1-hydroxypyrene, (1-p…
Magneto-structural correlations in Ni(ii) [2 × 2] metallogrids featuring a variable number of μ-aquo or μ-hydroxo extra bridges
2019
Four new [2 × 2] grid-type metallosupramolecular species have been obtained by using the ditopic 3,6-bis(2′-pyridyl)pyridazine ligand (dppn) and nickel(II) salts containing poorly coordinating anions. Three of them have the formula [Ni4(μ-dppn)4(μ-OH)2(μ-H2O)2]X6·nH2O [with X = ClO4− (1), NO3− (2) and CF3SO3− (3), and n = 6.5 (1), 14 (2) and 4 (3)]. Their crystal structure shows the same tetranuclear core, constituted by four six-coordinate metal ions and four dppn molecules. Two hydroxo groups and two water molecules efficiently interact forming two hydrated hydroxide (H3O2−) supramolecular bridging anions, further stabilizing the grid. The other compound, [Ni4(μ-dppn)4(μ-OH)3(μ-H2O)](ClO4…
Bipyridine based metallogels: an unprecedented difference in photochemical and chemical reduction in the in situ nanoparticle formation
2017
Metal co-ordination induced supramolecular gelation of low molecular weight organic ligands is a rapidly expanding area of research due to the potential in creating hierarchically self-assembled multi-stimuli responsive materials. In this context, structurally simple O-methylpyridine derivatives of 4,4′-dihydroxy-2,2′-bipyridine ligands are reported. Upon complexation with Ag(I) ions in aqueous dimethyl sulfoxide (DMSO) solutions the ligands spontaneously form metallosupramolecular gels at concentrations as low as 0.6 w/v%. The metal ions induce the self-assembly of three dimensional (3D) fibrillar networks followed by the spontaneous in situ reduction of the Ag-centers to silver nanopartic…
A post-synthetic approach triggers selective and reversible sulphur dioxide adsorption on a metal-organic framework.
2018
We report the application of a post-synthetic solid-state cation-exchange process to afford a novel 3D MOF with hydrated barium cations hosted at pores able to trigger selective and reversible SO2 adsorption. Computational modelling supports the full reversibility of the adsorption process on the basis of weak supramolecular interactions between SO2 and coordinated water molecules.