Long-Chain Linear Oligogermanes and Polygermanes with Tunable Optical and Electronic Properties: Steps Toward the Design of Tailored Molecular Electronics

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With this award, the Chemical Synthesis Program of the Division of Chemistry is funding Professor Charles S. Weinert of Oklahoma State University to synthesize molecules that contain chains of germanium atoms (oligogermanes). Systems with very long germanium chains and germanium nanomaterials are known to have important electronic and optical properties that depend on the number of germanium atoms in the chain and on the other groups appended to the chain. In this study, both the number of germanium atoms and the substituent groups are carefully controlled. Since the properties of these molecules can be tuned by variation of their composition, discrete molecules with specific absorbance, emission, and conductive properties can be designed and prepared. The broader impacts include the development of conductive new materials with tunable optical properties that may be used in lenses, detectors, or other optical applications. In addition to the education and training of graduate students, the project will involve Native American high school or undergraduate students from Oklahoma with the ultimate goal of inspiring these students to pursue careers in science. Singly-bonded catenates of germanium are of interest sigma-delocalization that results in interesting optical and electronic properties that can be tuned by varying their composition. Recent DFT calculations indicate that polygermanes, and potentially oligogermanes, can function as quasi-one dimensional semiconductors with a direct bandgap, where the valence and conduction bands result mainly from the catenated germanium skeleton. In this project, the Weinert research team is undertaking the synthesis of a diverse array of long-chain linear oligogermanes in order to ascertain if these new molecules will exhibit useful optical and/or conductive attributes akin to the polygermane analogues. The new molecules prepared in these investigations are characterized by a variety of techniques, including NMR, UV/visible, emission spectroscopy, cyclic and differential pulse voltammetry, high-resolution mass spectrometry, and X-ray crystallography. Studying the solid-state structures of these molecules is important since the overall geometry of the oligogermane affects its physical properties. Another aspect of this project involves the incorporation of oligogermanes into the graphite electrodes of high-end batteries in order to improve the overall performance of these systems, and these studies are being done in collaboration with a research team at Technical University in Graz, Austria. The photochemistry of these oligogermanes is being investigated, with the goal of affecting photochemical rearrangements of these molecules to new species that are not available by purely synthetic routes.