Synthesis and photoluminescent properties of linear and starburst compounds based on benzimidazole, 2-(2'-pyridyl)benzimidazole and 2,2'-dipyridylamine
White, Wade M.
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The objective of this thesis was to explore the chemistry of series of linear and star shaped compounds based on benzimidazolyl, 2-(2’-pyridyl)benzimidazolyl, and 2,2’-dipyridylamino functional groups. These groups all possess Lewis base sites suitable for metal coordination, and are all known fluorophores. The first compounds to be presented are the homo-substituted benzimidazolyl derivatives. Compounds 2.1-2.5 have been fully characterized and are all luminescent with emission energies in the UV region. While coordination complexes with these ligands have not been isolated, the effect of metal ion complexation on ligand luminescence has been explored via metal ion titration experiments. Furthermore, these compounds all have electron affinities greater than -3.0 eV and large optical bandgaps that range between 3.55 and 3.95 eV. These compounds also have high thermal and morphological stability. In light of this, compound 2.3 was selected as a representative example, and further characterized as an electron transport/hole blocking material for OLED applications. It has demonstrated a performance comparable to that of the well known electron transport material Alq3 (q = 8-hydroxyquinolinate). The second class of compounds, 3.2 and 3.3, represent a pair of hetero-substituted ligands with two different binding sites available for coordination chemistry. A copper (I) complex of 3.3 has been isolated and exhibits orange phosphorescence at room temperature and at 77 K. Furthermore, a series of metal titration experiments have been performed on 3.3 and 3.4, and have demonstrated the preference of different metal ions for either the 2,2’-dipyridylamino site, or the 2-(2’-pyridyl)benzimidazolyl binding site. The details of these explorations will be presented in the subsequent chapters.