Date of Graduation

Summer 2010

Degree

Master of Science in Chemistry

Department

Chemistry

Committee Chair

Erich Steinle

Keywords

HOMO-LUMO, bandgap, HOMO-LUMO tuning, fluorenylidene, bifluorenylidene, fluorenimine, fluorenone, electrochemical bandgap, donor-acceptor pair

Subject Categories

Chemistry

Abstract

Fluorenones and related derivatives have been explored in many studies for the development of organic-based semiconducting materials. In such materials, the size of the bandgap and the relative energy levels of the highest-energy occupied molecular orbital (HOMO) and the lowest-energy unoccupied molecular orbital (LUMO) must be correct for proper charge transfer to occur. A study of the effects of molecular structure changes on the HOMO-LUMO bandgap and HOMO-LUMO levels for a series of 9-fluorenones, fluorenylidenes, and related derivatives is herein described. Electrochemical and optical measurements were used to calculate the HOMO-LUMO levels and bandgap for each structure, and the results from both methods were compared and correlated to the changes in molecular structure. Electron-donating substituents were observed to decrease the HOMO-LUMO bandgap and increase the energy levels of the HOMO and the LUMO, while electron-withdrawing substituents were observed to produce the opposite effects. Increasing conjugation produced similar results, but the LUMO level was observed to decrease. Increasing the availability of nonbonding electrons changed the nature of the electronic transition, decreasing the efficiency but decreasing the bandgap. These studies provide insight into developing materials with specific conductive properties and specifically tuned HOMO and LUMO levels for a variety of applications.

Copyright

© Galen L. Eakins

Campus Only

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