Studies on Novel Organic Redox Systems Containing Heterocycles with High Electron Affinities and Their Applications in the Study of EL Devices

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There has been considerable interest in new carrier-transporting materials for the research and development of organic electroluminescent (EL) devices. These materials are important for the effective recombination between electrons and holes in the emitting layers. With regard to this, we have designed and synthesized new organic redox systems with high electron affinities such as ligands and complexes, oligomers and polymers, and macrocycles.1.Ligands and Complexes(1)In order to investigate an effective method for carrier injection into the phosphor of organic EL devices, we synthesized new phosphorescent materials containing hole-trapping moieties. Organic EL devices using these materials as emitters exhibited high EL efficiencies. (Eur. J. Inorg. Chem. 2006, 3675)(2)We synthesized BF_2 complexes with various 1,3-diketone ligands and their optical, electrochemical, and structural properties were investigated. These boron complexes are candidates for the fluorescent dopants of emitting layers.(3)We synthesized a ruthenium(II) complex containing a 4,5-diazafluorene moiety as an electron-transporting polypyridyl ligand. A solar cell using the complex as a dye sensitizer showed a high solar energy-to-electricity conversion efficiency.2.Oligomers and PolymersAcene dimers linked by a 1,3,4-oxadiazole spacer were synthesized and their physical, optical, and electrochemical properties were investigated. These molecules were perpendicularly arranged on a SiO_2 substrate to form π-stacking films as observed in the X-Ray diffraction analysis. (Heterocycles 2007, 72, 85)3.MacrocyclesThe macrocyclic tetramer of 2-phenyl-1,3,4-oxadiazole was synthesized and its self-assembly was investigated. In the crystal, the molecule was stacked along the c axis to form a one-dimensional columnar structure that internally contained a string of water molecules. The unique nanotube structure is a promising candidate in the study of nanotechnological applications. (patent application)