Substituted cage amines: towards new functional metalloassemblies

Chapter 1 contains an Introduction to the role of metal complexes in functional assemblies. The remainder of the chapter is devoted to an Introduction to the "sarcophagine" class of ligands, including their synthesis, stereochemistry and electrochemical properties. Chapter 2 describes the synthesis of a variety of alkylated derivatives of the cage amines "diaminosarcophagine" and "aminomethylsarcophagine". Procedures have been developed for the selective functionalisation of the primary amine sites through protection of the secondary amines by coordination to a metal ion. Experiments with the Cu(II) complex of diaminosarcophagine indicated mono-, di-, and tri-alkylation were possible by varying the reaction conditions but separation of the various alkylation products was extremely difficult. Methods were developed, therefore, to prepare the desired di-alkylated products in a selective manner which overcame the need for difficult and tedious separations. A method for the isolation of the free aminomethylsarcophagine ligand in good yields was developed. Copper and magnesium complexes of this ligand were prepared, which allowed the selective synthesis of monoalkylated cages. Magnesium(II) complexes were employed to successfully protect the secondary amines, and allowed the ready removal of the metal ion from the cage to give the free alkylated ligands. These ligands could then be used to prepare a variety of metal complexes containing one or two alkyl groups. Chapter 3 describes attempts to prepare thermotropic metallomesogens (liquid crystals) of a variety of cage complexes. The simple mono- and di-alkylated compounds described in Chapter 2 were shown not to form thermotropic LC phases and new complexes containing three and six alkyl groups were prepared in the hope of producing mesogenic behaviour. None of the compounds synthesised exhibited thermotropic liquid crystalline phases but the aqueous solution behaviour of the triple tailed complexes displayed interesting phenomena, most notably the production of viscoelastic solutions at ≤ 1 wt%. This behaviour was shown, in the case of the Co(III) complex, to be due to the presence of long cylindrical or "wormlike" micelles in pure water, which can be readily converted to vesicle structures. The electrochemical behaviour of the Co(III) complex displayed some interesting adsorption behaviour at a hydrophobic electrode surface giving an immobilised film. Chapter 4 describes the synthesis and characterisation of a series of Co(III) complexes linked by short peptide-like disulfide spacers. The solution electrochemical characteristics of the new complexes is reported. Two immobilisation methods, namely electrodeposition and traditional "self-assembly", were investigated for the preparation of monolayers of the disulfides on gold surfaces and both were found to give indistinguishable equilibrium surface coverages and electrochemical characteristics. An initial induction period was observed, most evident for the electrodeposited films, and this phenomenon has been tentatively assigned as due to a surface rearrangement effect.