Supramolecular self-assembly strategies involving water soluble calixarenes / Irene Ling

Ling, Irene (2010) Supramolecular self-assembly strategies involving water soluble calixarenes / Irene Ling. PhD thesis, University of Malaya.

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Abstract

Fundamental investigations of host-guest interactions on the supramolecular self-assembly involving water-soluble p-sulfonatocalix[4]arene, with a series of imidazolium-based cations and pyrrolidinium cation with variable alkyl chain lengths, which featured extensively in ionic liquids have been established. Combinatorial studies incorporating multiple components concerning p-sulfonatocalix[4]arene, imidazolium cations or pyrrolidinium cation, phosphonium cations and lanthanide ions have been developed, which yielded diverse solid state motifs with a common structural characteristic that the imidazolium or pyrrolidinium cation resides in the cavity of the calixarene. Shorter terminal alkyl chain of mono-imidazolium molecules, i.e. n-ethyl and n-butyl imidazoliums are confined in the „molecular capsule‟, being encapsulated by two calixarenes and coordinated by lanthanide metal ions, whilst terminal alkyl chain longer than n-butyl will have the alkyl chain directed away from the calixarene cavity. Longer terminal alkyl chain from the imidazolium cation also results in penetration into the adjacent calixarene bilayer. Calixarenes end-capping bis-imidazolium cation effectively creates „molecular capsule‟ or skewed „molecular capsule‟. The mono- or bis-phosphonium cations as part of the self-assembled material are not being taken up in the cavity nevertheless are self-assembled in between the calixarene bilayers, creating thicker hydrophobic bilayers and in some cases forms scaffold network which shroud the calixarenes. The nature of the interplay of the multi-component systems is well understood using Hirshfeld surface analysis and solution studies, with the results further highlighting the power of the technique in mapping out the interactions in a complex system, and how the components come together with complementarity interactions. The research was deemed as an important strategy in defining the limits in utilising the ubiquitous imidazolium cations or pyrrolidinium cation in constructing multi-component bilayers.Complexation of p-sulfonatocalix[4]arene with carbon rich nanomaterials i.e. single wall carbon nanotubes (SWNTs) and fullerenes (C60 and C70) shows these nanomaterials can be solubilised and stabilised in water by solventless mechanical grinding the component with p-sulfonatocalix[4]arene, followed by sonication in water This approach has possibilities in using other amphiphiles in solubilising carbon nanomaterials in general, where other techniques for dispersing such material are limited. The composite material has nano-particles of the calixarene randomly arranged on the surface of the carbon nanotube or fullerenes which render the hydrophobic material soluble in aqueous solution. However solubilisation is not possible when the two components are sonicated only in water without prior grinding.

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