The design, synthesis and study of transition metal-based cyclophanes and molecular materials for sensing and sieving applications

While much effort has been invested in the design and synthesis of transition metal-based cyclophanes of varying size and shape, comparatively little work has been done in developing them into usable sensors and platforms for ultrafiltration and catalysis. Existing proof-of-concept experiments have demonstrated solution-phase host:guest binding interactions via NMR and luminescence studies, but chemoresponsive molecular materials of this kind have not been described. This thesis describes: (a) the development of a gas-phase sensor, (b) a novel approach to the size and purity characterization of supramolecular assemblies via pulsed-field gradient NMR, and (c) the synthesis, characterization, and study of transition metal, cyclophane-based polymeric membranes for sieving applications.; This first study describes the development of a gas phase sensor based on thin films of molecular materials (molecular squares, rectangles and corners) sensitive to volatile organic compounds. These materials were found to be both size and chemical-composition selective.; The second study focuses on the synthesis and characterization of porphyrin-based molecular squares derivatized with functional groups capable of polymerization. These squares, based on trans [5,15-(4-ethynylpyridine)-10,20-(4-substituted-phenyl)porphyrin ligands with tricarbonylrhenium(I) corners, were not amenable to standard size characterization via FAB-mass spectrometry, due to their higher molecular weights (4700 to 5300 g/mol). A novel approach to size and purity characterization was devised utilizing pulsed-field gradient NMR spectroscopy—a technique that reports on self-diffusion coefficients. These scale inversely with hydrodynamic radii, which in turn scale approximately with molecular weight.; These functionalized cyclophanes were then used as monomers in interfacial polymerization reactions with di-functional crosslinkers to form molecular square-based membranes. The molecular square subunits within the polymeric membranes were found to be ordered (by polarized absorption studies) with the channels at approximately 34 degrees to the surface normal. Placement of the membranes over a conductive platform allowed for electrochemical investigation of their porosity and molecular sieving properties. The polymeric membranes yielded permeation rates 10-fold higher than those observed for analogous disordered, molecular films.; Finally, the synthesis and characterization of novel dimeric assemblies utilizing cis [5,10-(4-pyridyl)-15,20-(4-substituted-phenyl)porphyrin ligands, are also described. These assemblies will serve as platforms for electron- and energy-transfer studies.