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Synthesis, Characterization and Photophysical Studies of Porphyrin and N-Confused Porphyrin Derivatives and Self-assembled Nano-Morphologies

Acharya, Rajendra

Abstract Details

2013, Doctor of Philosophy, University of Akron, Chemistry.
Organic photoactive molecules and polymers are gaining much attention due to their potential applications in organic photovoltaic devices and organic electronics. Organic photovoltaic devices suffer from low efficiencies that result from low charge carrier mobilities and short exciton diffusion lengths. To increase the efficiency of organic photovoltaic devices, much of the focus of current research in this field is on panchromic organic molecules, suitable donor-acceptor molecules and self-organized organic semiconductors. Controllable nano-morphologies of donor and acceptor molecules via self-assembly, together with structured interfaces which are important for efficient charge separation and transport, may reduce the problems and yield photovoltaics with much higher efficiencies. Porphyrins are stable, largely planar, aromatic macrocycles, which makes them excellent at forming aggregates by way of pp-interactions. Their aromatic structures and resulting favorable redox and excited state properties, in turn, make them excellent model compounds for the study of photo-induced processes. N-Confused porphyrins are structural isomers of porphyrins which show physical and chemical properties different than that of regular porphyrins. N-Confused porphyrins are interesting molecules due to their structure, reactivity, solvent dependent tautomerization and metal binding properties. This dissertation presents synthetic methods to design new derivatives of porphyrins and N-confused porphyrins to obtain new photophysical properties as well as incorporate these molecules into self-assembled nano-morphologies. Several forms of intermolecular interactions are used in non-covalent syntheses and self assembly, most prominently hydrogen bonding and p-stacking interactions. Porphyrins substituted with peripheral polyalkyl chains have been shown to have liquid crystal properties and usually form columnar mesophases within certain temperature ranges. In the first project of this dissertation, several meso-subtituted tetraarylporphyrins have been synthesized, where the porphyrin macrocycle is attached using different types of linkages to a phenyl ring bearing trialkoxy groups. The effect of the linker in aggregations of these porphyrins via peripheral interactions, such as through the formation of hydrogen bonds and dipole interactions, between porphyrins is presented. The morphology of these porphyrins in drop cast thin films, as well as their aggregation behavior in solution, as a function of the combined p-stacking and H-bonding properties is also presented in this dissertation. Porphyrins with ester, hydrazide and ethylenediamide (EDA) linking groups between the porphyrin macrocycle and the trialkoxy aryl groups were observed to self-assemble in solution and in thin films. TEM studies of these porphyrins revealed nano-fiber formation from methylcyclohexane (MCH) and chloroform solutions. In the second portion of this dissertation a series of asymmetrically substituted N-confused porphyrins were synthesized using N-confused and regular dipyrromethanes. The structures of these compounds were confirmed by various 2D NMR techniques. This project represents the first synthesis of asymmetrically substituted N-confused tetraarylporphyrins. In a third project, a series of tetrasubstituted N-confused porphyrins having different linking groups between the N-confused porphyrin macrocyle and trialkoxyaryl groups were synthesized. The photophysical properties and morphologies of these meso-substituted N-confused tetraarylporphyrins (NCTArPs) are described. These molecules were found to assemble into nano-fibers and nano-rods, most likely because of H-bonding interactions between the NCPs. This work represents the first report on NCPs self-assembly into arrays. Finally, NCPs were shown to undergo reaction with nitromethane to produce nitromethane substituted NCPs which have very different photophysical properties from NCPs.
David Modarelli, Dr. (Advisor)
Michael Taschner, Dr. (Committee Member)
Chrys Wesdemiotis, Dr. (Committee Member)
Matthew Espe, Dr. (Committee Member)
Kevin Cavicchi, Dr. (Committee Member)
194 p.

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Citations

  • Acharya, R. (2013). Synthesis, Characterization and Photophysical Studies of Porphyrin and N-Confused Porphyrin Derivatives and Self-assembled Nano-Morphologies [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1376061548

    APA Style (7th edition)

  • Acharya, Rajendra. Synthesis, Characterization and Photophysical Studies of Porphyrin and N-Confused Porphyrin Derivatives and Self-assembled Nano-Morphologies. 2013. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1376061548.

    MLA Style (8th edition)

  • Acharya, Rajendra. "Synthesis, Characterization and Photophysical Studies of Porphyrin and N-Confused Porphyrin Derivatives and Self-assembled Nano-Morphologies." Doctoral dissertation, University of Akron, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1376061548

    Chicago Manual of Style (17th edition)