Synthesis Of Functional Metallosupramolecular Complexes

This thesis describes three areas of research which involve preparation of novel pyridyl-thiazole-containing ligands and the formation of their complexes with transition metal ions. Chapter 2 describes the preparation, complexation chemistry and photophysical behaviour of ligands L1 and L2 which contain pyrene moieties. The emission properties of pyrene are highly dependent on its environment, and so it was proposed that it could be used as a probe to elucidate solution conformations of complexes. It was shown that incorporation of a pyrene moiety into the ligand strand and subsequent measurement of the emission spectra of its complexes with Cu+ and Cd2+ gave information about their solution state conformations which correlated well with the solid state structures. In Chapter 3, synthesis and coordination complexes of ligands L3 and L4, which contain substituents capable of binding anions, are described. L3 forms a mononuclear complex with Zn(II) which binds two perchlorate anions via the amide groups on the two substituents. However, with Cu(I), L3 and L4 form dinuclear double helicates which have a binding "pocket" at each end of the complex. Both [Cu2(L3)2](ClO4)2 and [Cu2(L4)2](PF6)2 form one-dimensional polymers; the complexes are held together by bridging perchlorate and hexafluorophosphate anions, respectively. Finally, in Chapter 4, allosteric control of the complexation behaviour of ligand L5 is described. L5 contains amine groups on the 3,3'-positions of the bipyridine core which can react with ketones, forming a cyclic aminal product. Reaction with cyclohexanone was used to control the metal specificity of the ligand by restraining the torsion angle between the two pyridine groups and forcing the ligand into planarity. In general, L5 formed dinuclear double helicates with tetrahedral metals and mononuclear complexes with octahedral metals, as expected. Upon reaction with cyclohexanone, mononuclear species were observed with Hg2+, Zn2+, Cd2+ and Ag+. Experiments were then carried out with mixtures of metal ions and two trends were observed: firstly, when L5 is mixed with octahedral and tetrahedral metals, species containing the octahedral metal are favoured. Where two octahedral metals are used species containing the metal with the larger ionic radius are formed preferentially. After reaction with cyclohexanone, only mononuclear species of the octahedral metals are observed in every case.