Kazuo Ono

A new synthesis of pyrroles and porphyrins fused with aromatic rings

Pyrroles fused with aromatic rings (isoindole derivatives) have been readily prepared by the reaction of aromatic nitro compounds with ethyl isocyanoacetate in the presence of DBU. The ease of this reaction depends on the aromaticity of the starting nitro aromatics. Polycyclic aromatic nitro compounds such as 1-nitroacenaphthylene or 9-nitrophenanthrene are more reactive than simple nitro aromatics such as nitrobenzene or nitronaphthalenes and give the corresponding pyrroles in good yields. Pyrroles prepared by this method have been converted into porphyrins fused with various aromatic rings by the reduction with LiAlH4 followed by treatment with an acid catalyst and oxidation with chloranil or oxygen. Tetra-1,2-naphthoporphyrin has been prepared by the reaction of 2-nitro-3,4-dihydronaphthalene or 1-nitronaphthalene with ethyl isocyanoacetate followed by reduction, tetramerization and oxidation. Thus, highly conjugated porphyrins are readily prepared starting from aromatic nitro compounds, and their electronic and optical properties can be controlled by choice of the starting aromatic nitro compound.

Synthesis of pyrroles annulated with polycyclic aromatic compounds; precursor molecules for low band gap polymers

Pyrroles annulated with polycyclic aromatic compounds, which are expected to be good precursor molecules for low band gap polymers, are prepared by the reaction of aromatic nitro compounds with ethyl isocyanoacetate and the subsequent deethoxycarbonylation.

Highly efficient coupling between two planar waveguides with different refractive index profiles by using nonlinear cladding

An efficient butt-joined coupling scheme between single-mode planar waveguides with different refractive index profiles is proposed. The configuration consists of a tapered waveguide with nonlinear cladding. Power dependent coupling efficiency of the configuration is analyzed by the beam propagation method. The numerical results show that this configuration has high-coupling efficiency and is less sensitive to the offset between coupled waveguides if the input power is properly selected.<<ETX>>

Propagation characteristics of circularly bent gradient-index planar waveguides with finite cladding thicknesses

Circularly bent gradient-index planar waveguides with finite cladding thicknesses are analyzed by the modal matching method. The waveguides assume the refractive index profiles of different shapes, namely, the parabolic and the truncated parabolic profiles. Numerical results of propagation characteristics together with pure bend loss are shown. In addition, feasibility of interferometric devices using bent planar waveguide is discussed.