Functional polyoxometalate assemblies: from host-guest complexes to porous frameworks

Streb, Carsten (2008) Functional polyoxometalate assemblies: from host-guest complexes to porous frameworks. PhD thesis, University of Glasgow.

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The host-guest chemistry of two sets of isopolyoxometalate clusters is investigated. In particular the binding modes of cationic alkali and alkali earth metals through coordinative interactions with the cluster anions {Mo36} and {W36} were compared and contrasted. It was shown that the ionic radii of the cations are crucial in the isolation of discrete molecules or infinite 3D frameworks. Crystal engineering allowed the introduction of organic amine guest molecules by the formation of a set of intermolecular interactions between the cluster anions and the amine cations. In addition it was shown that by engaging the ammonium guest molecules in additional supramolecular interactions, the framework assembly in the solid state could be directed.

Further investigations focused on the assembly of supramolecular polyoxometalate-based framework materials where organic ammonium cations were used as hydrogen-bond donors. The structural effects of three amines were compared and contrasted and it was established that the use of rigid planar molecules resulted in the formation of 2D networks whereas the use of flexible amines gave supramolecular 1D chains. Based on these results the synthesis of a functional framework was achieved; a three-component approach allowed the formation of a chiral, porous framework which shows structural stability and reversible solvent sorption properties.

In a different approach, the cross-linking of polyoxometalates using transition metal linkers in organic solvents was studied. It was shown that silver(I) cations are highly versatile linking units and allow the linking of {V10} cluster anions into 1D zigzag chains and 2D planar networks. The silver units assemble into supramolecular, trinuclear complexes which are supported by bridging organic ligands. Careful choice of the reaction conditions allowed the formation of a 3D framework based on {W12} units. The tungstate clusters are cross-linked by dinuclear {Ag2} linkers which are held together by argentophilic silver-silver interactions and result in the formation of a porous framework. The material features reversible sorption capabilities and can be used to sequester small molecules as well as transition metal cations from organic solvents.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: polyoxometalates, frameworks, host-guest complex, chemistry, inorganic, materials, building blocks, porosity, sorption
Subjects: Q Science > QD Chemistry
Colleges/Schools: College of Science and Engineering > School of Chemistry
Supervisor's Name: Cronin, Prof. Leroy
Date of Award: 2008
Depositing User: Mr Carsten Streb
Unique ID: glathesis:2008-120
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 25 Jun 2008
Last Modified: 10 Dec 2012 13:15

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