Optical and electrochemical transduction of calixarene host-guest chemistry

The well-known selective receptor properties and ease of structural modification makes calixarene derivatives attractive materials for use in chemical sensors. This thesis represents a study of the performance of a range of calixarene compounds either as the active component of an optical sensor or as the lonophore in potentiometnc sensors. Determination of enantiomeric purity has become important in recent years due to increasing restrictions on the composition of pharmaceuticals whose efficacy depends on a chiral moiety. With the aim of enantiomeric selectivity, three novel fluorescent calixarenes were synthesised and their interaction with R and S enantiomers of phenylethylamine and norephedrine were investigated Stem-Volmer plots were used to evaluate the calixarenes and from this it was found that the calix[4]arene with a dinaphthylprolinol group attached to the lower nm exhibited the best selectivity of the three compounds investigated. Using this compound it was possible to determine the percentage of one enantiomer in the presence of the other. In keeping with the increasing popularity of optical modes of transducing host-guest interaction o f calixarenes, an ammonia gas optical sensor based on the nitrophenylazophenol cahx[4]arene ligand was developed. The optode membranes were prepared from a PVC cocktail composition and exhibited significant colour change on exposure to gaseous ammonia. Some preliminary studies involving coated optical fibres together with a mass flow controller were also earned out demonstrating the potential of this chromogemc calixarene for the detection of ppm levels of ammonia. The performance of sodium selective electrodes based on the monoacid denvatives of tetramethyl and tetraethyl /?-fert-butylcalix[4]arenes were investigated Virtually no difference in selectivity between the monoacid denvatives and the tetraesters was found pH stability studies showed that the monoacid denvatives gave best performance at neutral pH but at alkaline pH there was a reduction in response which did not occur with the tetraesters. A PVC membrane electrode based on an alklylated calix[4]arene tetraphosphine oxide was developed and found to be selective for europium (III) m the presence of a high background of sodium and other common ions. The results also suggest that there is some selectivity within the lanthanide senes itself. Two other tetraphosphine oxide calixarene denvatives were also evaluated but were found not to be as selective as the alkylated calix[4]arene tetraphosphine oxide