Structure Activity Study of a Family of Functional Pyrene-Isoxazole-Calix[4]arene Fluorescent Chemosensors for Metal Ion Detection

This thesis reports onthedesign, synthesisand structural characterisationof a novel family of pyrene-isoxazole-calix[4]arenes. Aninvestigation of their metal cation sensing abilitiesusing techniques including absorbance, fluorescence and 1H NMR spectroscopiesfollows.The novel work begins by developing apyrene-isoxazole appended calix[4]arene,PIC thatcould selectively detectand report, viafluorescence spectroscopy, on the presence ofCu2+ions in MeCN. Thehost:guest binding interactionwas investigated by 1H NMR spectroscopy.Stern-Volmer analysis of the quenching mechanism, Benesi-Hildebrand analysis of the binding constant and detection limit calculations were performed in characterisation of the binding properties of this host.The relationship betweenthe modular building blocks and the conformational presentation of thehost structuresand their metal cation sensing abilities was probed by design of three new members of this family,structurally related to PIC. Each memberdifferedat just onekey position. EPIC, introduced an ethylene linker between the lower rim of the calixarene and the isoxazole heterocycle, PPICintroduced an alkyl chain between the isoxazole rings and the pyrene units and MPICincorporatedmethoxy groups in place of the hydroxyl groups of PIC.Each host wassuccessfully synthesised using catalyst-free click cycloaddition and were structurallycharacterisedusing the full suite of analytical techniques including solid state structures of EPIC and MPIC.Fluorescence spectroscopic studiesindicated thatwhilstEPIC, PPIC and MPIC, like PIC, had affinities forCu2+binding, there were subtle differences in the binding association of the H:G complexes (Kavalues varied between 33,000–6,000 M-1) and in the information that could be extracted from the NMR spectroscopic study of their binding.In order to probe real-world applications such as waste water analysis,studies involving PIC in aqueous MeCN were conducted. Atendencyfor the hosttoself-assemble andform supramolecular structures in the aqueous media was hypothesised on the basis of emission and absorbance data and supported by SEM images.PIC was shown to be fluorescent in drop-casted solid state samplesand subsequently in electrospun PIC doped polymeric microfibers. The fluorescent microfibers responded spectrofluorometrically tothe presence of Cu2+ cations in water