Charge migration in supramolecular assemblies with multiple redox centers

The relationship between molecular structure and charge migration within supramolecular assemblies containing multiple redox centers is the primary topic of this thesis. The supramolecular assemblies are comprised of molecules with favorable attributes for use in organic electronic and light-harvesting applications. The main techniques employed for the determination of charge migration are electron paramagnetic resonance (EPR) spectroscopy and electron nuclear double resonance (ENDOR) spectroscopy.;First, a series of zinc porphyrin arrays using meso-meso and meta-phenylene linkages comprised of dimers, tetramers, and a dodecameric ring were singly oxidized and intramolecular hole hopping between the porphyrin moieties was probed using EPR and ENDOR. Rapid hole hopping occurs between both porphyrins within both dimers, and among three porphyrins of the tetramers, and among 8-12 porphyrins in the dodecameric ring with rates > 107 s-1. These results show that hole hopping is rapid even though the meta-phenyl bridges and direct meso-meso linkages do not provide optimal electronic coupling between the porphyrins within these multi-porphyrin arrays.;Next, intramolecular electron hopping is explored within a series of synthetic DNA hairpins in which perylenediimides (PDIs) are cofacially stacked by incorporation into the DNA strands as base pair surrogates. Analysis of the EPR and ENDOR spectra of the singly reduced duplexes is consistent with electron delocalization over two sites in both dimers and the trimer and over three sites in the tetramer. These results demonstrate the potential of synthetic DNA scaffolds, readily obtainable using automated synthesis techniques, to promote large scale ordering and long distance charge transport in redox-active organic molecules.;Lastly, a series of linearly-linked PDI dimers and trimers were synthesized in which the PDI pi systems are oriented nearly orthogonal to one another. When the functional groups attached to the ends of the oligomers were chosen to make each PDI molecule electronically equivalent, the single electron in a mono-reduced sample hops between the PDI molecules with rates that significantly exceed 107 s-1. Rapid electron hopping between pairs of PDI molecules having orthogonal pi systems is unexpected and may expand the possible design motifs for organic electronic materials based on PDI.