Kazumasa Funabiki

Synthesis and fluorescence properties of thiazole-boron complexes bearing a β-ketoiminate ligand.

Novel fluorescent dyes, thiazole-boron complexes bearing β-ketoiminate ligands, have been synthesized, and their fluorescence properties were investigated. The BF(2) complexes showed a pronounced aggregation-induced emission enhancement effect because of the restriction of C-Ph intramolecular rotation. The BPh(2) complexes showed higher fluorescence quantum yields than the corresponding BF(2) complexes, both in solution and in the solid state.

Synthesis and Fluorescence Properties of Novel Pyrazine–Boron Complexes Bearing a β-Iminoketone Ligand

A novel fluorescence dye based on pyrazine-boron complexes bearing a β-iminoketone ligand has been synthesized by using a simple two-step reaction. Synthesized complexes exhibited fluorescence in solution (F(max): 472-604 nm) and in the solid state (F(max): 496-624 nm). These complexes showed a larger Stokes shift (3690-4900 cm(-1)) than well-known boron dipyrromethene dyes (400-600 cm(-1), in most cases).

Novel thiophene -conjugated indoline dyes for zinc oxide solar cells

The application of a series of thiophene-conjugated indoline dyes for zinc oxide solar cells, prepared by the one-step cathode deposition template method, was examined. The introduction of thiophene ring(s) into D131-type indoline dye improved the cell performance due to their appropriate energy levels and bathochromic shift in the UV-vis absorption band on zinc oxide. It is important for the oxidation potential (Eox) of dyes to have a more positive value than ca. 0.25 V vs. Fc/Fc+ in acetonitrile in order to show a high (>70%) incident photon-to-current efficiency.

Synthesis and Fluorescence Properties of a Pyridomethene−BF2 Complex

A fluorescent dye, the pyridomethene-BF(2) complex, has been synthesized. Although pyridomethenes did not exhibit fluorescence, pyridomethene-BF(2) complexes exhibited fluorescence both in solution and in the solid state. The trifluoromethyl-substituted BF(2) complex formed a J-aggregate and showed the highest fluorescence quantum yield in the solid state among all pyridomethene-BF(2) complexes.

Synthesis and Fluorescence Properties of Pyrimidine Mono- and Bisboron Complexes

Novel fluorescent mono- and bisboron complexes based on pyrimidine bearing β-iminoenolate ligands were synthesized, and their fluorescence properties were investigated. The nonsubstituted and trifluoromethyl-substituted monoboron complexes showed higher fluorescence quantum yield in solid state than in solution. The dimethylamino derivative of the monoboron complex exhibited positive solvatochromism in the fluorescence spectra. The bisboron complex showed significantly higher molar absorption coefficient and red-shifted maximum absorption and maximum fluorescence wavelengths than the corresponding monoboron complex.

Synthesis and properties of bis(hetaryl)azo dyes

Abstract Unsymmetrical and symmetrical bis(hetaryl)azo dyes were prepared by diazotisation-coupling and oxidation reactions in low to good yields. Their absorption maxima were observed in the range of 427–631 nm, being more bathochromic than the corresponding non-hetarylazo derivatives. No remarkable difference of decomposition temperature in the bis(hetaryl)azo dyes was observed except for the pyridone derivative. The photofading of benzothiazolylazo derivatives in ethanol in air occurred by way of reductive processes.

Design of NIR-absorbing simple asymmetric squaraine dyes carrying indoline moieties for use in dye-sensitized solar cells with Pt-free electrodes.

Novel near-infrared (NIR)-sensitizing (up to 800 nm) simple asymmetric squaraine dyes (Sq 31 and Sq 33) carrying indoline moieties that did not require the introduction of any linker groups were developed. DSSCs fabricated with Sq 33 exhibited remarkable characteristics in the long-wavelength visible and NIR region (up to 800 nm), such as a conversion efficiency of 3.75% (AM 1.5G) with an incident photon-to-current conversion efficiency of 63% (650 nm), a short-circuit photocurrent density of 13.64 mA, an open-circuit photovoltage of 0.48, and a fill factor of 0.57.

Organic dyes containing fluorene-substituted indoline core for zinc oxide dye-sensitized solar cell

A novel idoline dye, having dimethylfluorene-substituted indoline donor and dicyanovinylidene-introduced rhodanine acceptor (DN350), gave much higher efficiency than D205 due to bathochromic absorption band and prevention of aggregates formation.

Synthesis of a novel heptamethine–cyanine dye for use in near-infrared active dye-sensitized solar cells with porous zinc oxide prepared at low temperature

A novel near-infrared-absorbing heptamethine–cyanine dye (KFH-3) that contains four n-butyl groups was synthesized for use in highly efficient dye-sensitized solar cells with porous zinc oxide (ZnO) prepared at low temperature, and resulted in remarkable performance characteristics, such as a conversion efficiency of 1.23% (AM 1.5) with an incident photon-to-current conversion efficiency (800 nm) of 33%, a short-circuit photocurrent density of 3.34 mA, an open-circuit photovoltage of 0.49, and a fill factor of 0.76, using almost solely the near-infrared region of sunlight.

Solvatochromic Fluorescence Properties of Pyrazine–Boron Complex Bearing a β-Iminoenolate Ligand

Pyrazine-based monoboron complexes bearing two fluorine atoms (BF2 complex) or two phenyl groups (BPh2 complex) on the boron atom were synthesized, and the fluorescence properties were investigated. The BPh2 complexes exhibited red-shifted maximum absorption and maximum fluorescence wavelengths and lower molar absorption coefficients than the corresponding BF2 complexes in n-hexane. The fluorescence quantum yields of the BPh2 complexes were higher than or comparable to the corresponding BF2 complexes owing to the relatively low nonradiative rate constants. Although the nonsubstituted and trifluoromethyl-substituted derivatives did not show solvatochromism, the dimethylamino-substituted BF2 and BPh2 complexes exhibited pronounced solvatochromism in the fluorescence spectra. Dual fluorescence was observed for the dimethylamino-substituted BF2 complex in toluene, 1,4-dioxane, and chloroform, corresponding to locally excited (LE) and twisted intramolecular charge-transfer (TICT) states.