Irene Ling

Structural diversity of multi-component self-assembled systems incorporating p-sulfonatocalix[4]arene

Bowl shaped p-sulfonatocalix[4]arene is a versatile anion in building multi-component self-assembled materials, with a design strategy of incorporating small organic cations including imidazolium or pyrrolidinium cations within the cavity of the calixarene through their polar head groups, which is also established in solution for the two components. Another design strategy is the assembly of interlocking (embracing) large phosphonium cations around the outer (exo-) surface of the cavity of the calixarene. The selectivity of interplay of the different cations with the endo- and exo-surfaces of the calixarene requires the presence of aquated lanthanide(III) ions, but these ions are not necessarily incorporated into the extended structures.

Calixarene C8-imidazolium interplay as a design strategy for penetrating organic bi-layers

1-Octyl-3-methylimidazolium (C8-mim) cation forms multi-component bi-layers with p-sulfonatocalix[4]arene and phosphonium ions, and aquated lanthanide ions, with the imidazolium head group residing in the calixarene cavity and the terminus of the C8 chain penetrating the adjacent hydrophobic bi-layer which is comprised of calixarenes and phosphonium ions, as part of a porous-like extended structure. Hirshfeld surface analyses reveal the nature of the interactions between the components.

Lanthanoid assisted self-assembly of imidazolium cations in organic bi-layers

Multi-component solutions containing 1-n-ethyl-3-methylimidazolium or 1-n-butyl-3-methylimidazolium cations, p-sulfonatocalix[4]arene and large mono- or bis-phosphonium cations, as well as lanthanide metal ions, afford self-assembled material incorporating all four components. The calixarenes and phosphonium cations are organized into bi-layers, with the imidazolium cations and gadolinium(III) species incorporated between the bi-layers. The imidazolium cations are confined within essentially ‘molecular capsules’ based on two calixarenes from adjacent bi-layers, with these cations taking on different orientations, depending on the nature of the phosphonium cation, and whether the metal also binds to sulfonate moieties.

Structural and electrochemical characteristics of 49% PMMA grafted polyisoprene-LiCF3SO3-PC based polymer electrolytes.

Gel polymer electrolytes consisting of 49% PMMA grafted polyisoprene-LiCF3SO3, were plasticized with propylene carbonate (PC) are reported. The effect of PC on the electrochemical properties of the polymer electrolyte has been investigated. Analysis of FTIR spectra shows the interaction of salt and plasticizers with the polymer chain. The ionic conductivity was measured and exhibited a maximum value of 10−4 S/cm. The temperature dependence of the electrical conductivity follows the Arrhenius law.

Organocatalysis by p-sulfonic acid calix[4]arene: a convenient and efficient route to 2,3-dihydroquinazolin-4(1H)-ones in water

An efficient and eco-friendly method is reported for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones from the direct cyclocondensation of anthranilamide with aldehydes using p-sulfonic acid calix[4]arene (p-SAC) as a recyclable organocatalyst in excellent yields in water at room temperature. The catalyst was reusable without significant loss of catalytic efficiency. Operational simplicity, the compatibility with various functional groups, non-chromatographic purification technique, high yields and mild reaction conditions are the notable advantages of this procedure. Large scale reaction demonstrated the practical applicability of this methodology.

Selective Binding of Imidazolium Cations in Building Multi-Component Layers

Addition of 1-alkyl-3-methylimidazolium (C(n)-mim) cations 3-5 to a mixture of bis-phosphonium cation 2 and sodium p-sulfonatocalix[4]arene (1) in the presence of lanthanide ions results in the selective binding of an imidazolium cation into the cavity of the calixarene. The result is a multi-layered solid material with an inherently flexible interplay of the components. Incorporating ethyl-, n-butyl- or n-hexyl-mim cations into the multi-layers results in significant perturbation of the structure, the most striking effect is the tilting of the plane of the bowl-shaped calixarene relative to the plane of the multi-layer, with tilt angles of 7.2, 28.9 and 65.5 degrees , respectively. The lanthanide ions facilitate complexation, but are not incorporated into the structures and, in all cases, the calixarene takes on a 5- charge, with one of the lower-rim phenolic groups deprotonated. ROESY NMR experiments and other (1)H NMR spectroscopy studies establish the formation of 1:1 supermolecules of C(n)-mim and calixarene, regardless of the ratio of the two components, and indicate that the supermolecules undergo rapid exchange on the NMR spectroscopy timescale.

Multi-component bi-layers featuring [1-octyl-2,3-dimethylimidazolium ∩ p-sulfonatocalix[4]arene] supermolecules

Multi-component solid state structures containing 1-octyl-2,3-dimethylimidazolium cations, anionic p-sulfonatocalix[4]arenes and/or large mono-phosphonium cations, as well as lanthanide metal ions are readily accessible, which have the calixarenes organised into bi-layers with gadolinium(III) coordinated between them. The imidazolium ring is confined in the calixarene cavity, essentially forming “molecular capsules” based on two calixarenes, or with the n-octyl chain penetrating the adjacent bi-layer, with the nature of the calixarene–dimethylimidazolium interplay mapped out using Hirshfeld surface analysis. The supermolecules [1-octyl-2,3-dimethylimidazolium ∩ p-sulfonatocalix[4]arene] are persistent in aqueous solutions (1H NMR).

Supramolecular architecture containing end-capping bis-imidazolium cations

Multi-component self-assembly involving bis-phosphonium and bis-imidazolium cations, and p-sulfonatocalix[4]arene feature supermolecules based on two geometrically opposed calixarenes end-capping each bis-imidazolium cation, either with coordinated lanthanide cations or with the phosphonium cations residing around the upper rim of the calixarenes. The nature of the calixarene-bis-imidazolium interaction is mapped out using Hirshfeld surface analysis. 1H NMR and ROESY experiments establish the formation of the supermolecules of the bis-imidazolium cation and calixarenes in solution.

Hirshfeld surface analysis of phosphonium salts

Structurally authenticated phosphonium salts yielded from the treatment of (phosphoniumn+)(Cl− or Br−)n and (imidazoliumn+)(X−)n, n = 1 or 2 have been examined using Hirshfeld surface analysis, revealing the domination of C–H⋯X non-classical hydrogen-bonding between the cations and anions. The crystalline salts of (phosphoniumn+)(X−)n (X− = [SCN]−, [N(CN)2]−, [C(CN)3]−, [PF6]−, [CF3SO3]− or [N(CF3SO2)2]−) were formed by metathetical exchange in the presence of p-sulfonatocalix[4]arene and aquated gadolinium ions.

Water solublisation of single-walled carbon nanotubes using p-sulfonatocalix[4]arene

Single-walled carbon nanotubes (SWCNTs) are decorated with nanoparticles of p-sulfonatocalix[4]arene which render the nanotubes soluble in water. The nanocomposite was prepared by a solventless grinding method, followed by the additional of water then sonication. The non-covalently modified carbon nanotubes have been characterized using Raman, FTIR spectroscopy, fluorescence spectroscopy, transmission electron microscopy and thermogravimetric analysis.