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From small molecules to nano-scale architectures - A supramolecular approach

Posted on:2009-07-25Degree:Ph.DType:Thesis
University:Kansas State UniversityCandidate:Scott, Benjamin M. TFull Text:PDF
GTID:2441390002494658Subject:Chemistry
Abstract/Summary:
We have shown that supramolecular synthons can be used to construct discrete two or three component co-crystals and 1-D inorganic-organic chains and dramatically influence the arrangement of nanoparticle assemblies.;A collection of supramolecular reagents (SR's) have been designed and synthesised to carry out a systematic study into hydrogen bonding. In order to test Etter's guideline "the best proton donor and acceptor remaining after intramolecular hydrogen-bond formation will form an intermolecular hydrogen-bond" and to develop a hierarchy of interactions, a series of co-crystals between the supramolecular reagents and hydrogen-bond donors (carboxylic acids) have been synthesised.;Co-crystals with pyrazole benzamide SR's have demonstrated the ability to fine-tune hydrogen-bond formation. By utilising a poor hydrogen-bond acceptor (pyrazole) the incoming carboxylic acid opts to form a heteromeric acid-amide dimer via N-H···O hydrogen bonds. Additionally, we have shown that the hydrogen-bond acceptor strength of the pyrazole can be turned up through simple covalent modifications (i.e. isomer change or addition of methyl groups to the pyrazole ring). Although the heteromeric acid-amide dimer is observed, O-H···N hydrogen bonds to the pyrazole are also observed in cases when more than one donor site is present (i.e. di-carboxylic acids and 4-hydroxybenzoic acid).;Furthermore, co-crystals with picolyl-indazole and pyrimidine-pyrazole SR's agree with Etter's guideline. In all cases, the incoming carboxylic acid forms an O-H···N hydrogen bond to the best acceptor (pyridine and pyrazole, respectively).;The homomeric amide-amide dimer has been used to construct inorganic-organic hybrid materials. The reaction between the pyrazole benzamide ligands with acac or "paddle-wheel" complex ions yielded 1-D chains. Furthermore, pyrimidine-bispyrazole and functionalised 1,3-bisbenzylpyrazole ligands have been utilised as chelating-ligands for reliable metal coordination.;Finally, the power of supramolecular synthons to control the arrangement of much larger nanoparticle assemblies has been shown. Both homomeric (acid-acid, alcohol-alcohol) and heteromeric (acid-imidazole, alcohol-imidazole) hydrogen bonding cause significant changes in nanoparticle assemblies.
Keywords/Search Tags:Supramolecular, Nanoparticle assemblies, Shown, Hydrogen, Co-crystals
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