Creation of Novel Organic Fluorophores Containing Benzofuran Rings

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Organic fluorophores are expected to play important roles in the extreme technology of 21st century as photoelectronics materials (e.g., organic electroluminescence diodes (OLEDs)). That is, these are expected to be not only the next generation of materials for the flat-panel display but also sources of light for illuminations, because the realization of white light-emitting may be possible on account of their flexibility of light-emitting color. In order to develop the further research in these fields, it is necessary to create the strongly fluorescent molecules at desired wavelength region. Under such circumstances, based on our previous results in regard to organic fluorophores, we have investigated on the creation of novel organic fluorophores and develop the general methodology. In conclusion, we have found out the following subjects.1.Phenyleneethynylenes containing pyridine rings : we have succeeded in creating very intense blue light-emitter, and found out that banana-shaped sy … More stems (having 2,6-disubstituted pyridine rings) show the greater light-emitting efficiency than the corresponding rod-shaped systems (2,5-disubstituted pyridine rings). Thus, we proposed the new concept that the higher emissive efficiency of banana-shaped systems might depend on the movability of the dipolar structural unit in the excited singlet state. This concept will be sure to make a contribution to creation of strongly fluorescent molecules.2.Linear-shaped systems introduced benzofuran rings to molecules : we have succeeded in the synthesis of very intense blue light-emitters having a single emissive maximum to suggest that the introduction of benzofuran rings to molecules is so effective for the creation of organic strongly fluorescent molecules.3.Rod-shaped oligo(aryleneethynylene)s (para-substituted systems) : we investigated the light-emitting efficiency tuning of rod-shaped oligo(p-phenylene ethynylen)s (OPEs, trimeric to pentameric systems) by donor- and acceptor-groups so that they emit the very intense fluorescence (Φ_f【approximately equal】1.0, log ε【approximately equal】5) at the desired wavelength region. This goal was achieved by side modification by MeO (donor) groups and end modification by CN-substituted benzene ring (or side modification by CN (acceptor) groups and end modification by NMe_2-substituted benzene ring) of tetrameric p-phenylene ethynylene rod-shaped molecule.4.Star-shaped oligo(aryleneethynylene)s (tiple mata-substituted systems) : we have investigated the light-emitting characteristics and occurrence of conjugation between arms of star-shaped rigid molecules that comprise a 1,3,5-tri-ethynylbenzene core, and methoxy group-substituted oligo(p-phenylethynylene)s arms. Consequently, we achieved the ultimate goal (Φ_f【approximately equal】1.0, log ε > 5) for organic molecules with respect to light-emitting ability by creating very intense violet-blue (Φ_f:0.97, log ε:5.11) and blue (Φ_f:0.98, log ε:5.29) bright light-emitters. Also π conjugation was found to occur between the arms of star-shaped rigid molecules despite the triple meta-substituted system. Less