Molecular machines constructed from multichromophore arrays
Our long-term ambitious goal is to construct molecular assemblies or machines of unprecedented complexity leading to unique function. Porphyrins and phthalocyanines have been selected as the building blocks for the construction of the targeted molecular machines. The synthesis of different porphyrin/phthalocyanine building blocks is introduced with particular emphasis on the introduction of central metal/metalloid elements such as ruthenium, indium and lanthanides. The linking of porphyrins to give covalent assemblies suitable for elaboration into machine-like arrays is then described. The synthesis of an array in which four porphyrin units surround a central porphyrin core is described, alongside modifications to the strategy that permits differential metal substitution. Strategies for face-to-face elaboration of machine-like structures from the previously described covalent multiporhyrin array are discussed. Although unsuccessful, a separate reaction pathway is described that leads to controlled formation of triple-decker structures. Model diporphyrins, linked through flexible spacers, are smoothly metallated with lanthanum. Complementary phthalocyanine macrocycles are then easily inserted, giving high yields of triple decker molecules. The synthesis and materials are discussed, and the novel structures are characterised by absorption spectroscopy, NMR spectroscopy and crystallography. The versatility and generality of the strategy are demonstrated by synthesis of analogues that incorporate more heavily functionalised central (phthalocyanine) macrocycles. Rotation is hindered (NMR) in these cases. Finally, preliminary assessment of extension of this approach towards higher-order stacks is described, alongside variation of the linking lanthanides to include magnetic elements such as dysprosium.
Networked Digital Library of Theses and Dissertations