Date of Award

Winter 2014

Project Type

Thesis

Program or Major

Chemistry

Degree Name

Master of Science

First Advisor

Glen P Miller

Second Advisor

Arthur Greenberg

Third Advisor

Eric Berda

Abstract

Organic semiconductors have been the subject of both academic and industrial interest due to their potential advantages over inorganic semiconductors. Based on the type of charge transporting (hole or electron), organic semiconductors can be categorized as n-type (electron transporting) or p-type (hole transporting). Most attention has been concentrated on the development of p-type organic semiconductors and their development has led to dramatic enhancements in the performance of hole transporting material. However, the investigation and application of electron transporting organic semiconductors has not drawn as much attention. In this project, we focus on the exploration, design, synthesis and characterization of novel n-type organic semiconductors.

A series of novel compounds, linearly extended thiazinium salts (LETS) with structures similar to methylene blue were designed. Methylene blue itself has several characteristics that are associated with potential n-type semiconductors, such as a positively charged backbone, water-solubility, stability, intense absorption in the visible region, a relatively small HOMO-LUMO gap, potential high charge carrier mobility and strong π-π stacking in its solid state crystal structure. A new molecule, 3,9-bis(dimethylamino)dibenzo[b,i]phenothiazin-6-ium chloride, was selected as one of several compounds for a computational (DFT) investigation for comparison to methylene blue. The calculated results showed that the new molecule has an even smaller HOMO-LUMO gap than 0.76 eV and a maximum absorption of light at approximately 790 nm. The computational study provided impetus to synthesize and characterize LETS compounds.

Three synthetic schemes have been explored for the synthesis of LETS compounds. A thionation reaction involving elemental sulfur, a coupling reaction and a Friedel-Crafts acylation have all been utilized to synthesize a precursor of LETSs, 13H-dibenzo[b,i]phenothiazine.

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