Masaru Matsuoka

The Variable iron k emission line in MCG-6-30-15

We report on the variability of the iron K emission line in the Seyfert 1 galaxy MCG--6-30-15 during a four-day ASCA observation. The line consists of a narrow core at an energy of about 6.4 keV, and a broad red wing extending to below 5 keV, which are interpreted as line emission arising from the inner parts of an accretion disk. The narrow core correlates well with the continuum flux whereas the broad wing weakly anti-correlates. When the source is brightest, the line is dominated by the narrow core, whilst during a deep minimum, the narrow core is very weak and a huge red tail appears. However, at other times when the continuum shows rather rapid changes, the broad wing is more variable than the narrow core, and shows evidence for correlated changes contrary to its long time scale behaviour. The peculiar line profile during the deep minimum spectrum suggests that the line emitting region is very close to a central spinning (Kerr) black hole where enormous gravitational effects operate.

Infrared absorbing dyes

1. Introduction.- I. Synthesis and Characteristics of Infrared Absorbing Dyes.- 2. Synthetic Design of Infrared Absorbing Dyes.- 3. Cyanine Dyes.- 4. Quinone Dyes.- 5. Phthalocyanine and Naphthalocyanine Dyes.- 6. Metal Complex Dyes.- 7. Photochromic Dyes.- 8. Other Chromophores.- II. Applications of Infrared Absorbing Dyes.- 9. Semiconductor Lasers.- 10. Optical Recording Systems.- 11. Thermal Writing Displays.- 12. Laser Printer Application.- 13. Laser Filter Systems.- 14. Infrared Photography.- 15. Medical Applications.

Fluorescence quenching by intermolecular π–π interactions of 2,5-bis(N,N-dialkylamino)-3,6-dicyanopyrazines

Abstract The fluorescence properties of 2,5-bis( N,N -dialkylamino)-3,6-dicyanopyrazine dyes in the solid state were correlated with their molecular stacking behavior. The optimized molecular structures were evaluated by using MOPAC PM3 and AM1 methods and their stacking behaviors of the π -chromophoric system were simulated from their three dimensional molecular structures and 1 H NMR spectra. The steric requirements of the substituents in the parent chromophoric system were the main cause of the spectral changes in the absorption and fluorescence maxima and fluorescence intensity in the solid state. Intermolecular π–π interactions effectively quenched the solid state fluorescence and, consequently, the degree of fluorescence quenching can be used as an indicator of intermolecular π–π interactions of fluorescence dyes chromophores. ©

New syntheses and solid state fluorescence of azomethine dyes derived from diaminomaleonitrile and 2,5-diamino-3,6-dicyanopyrazine

New fluorescent dyes of interest as red light emitters for electroluminescence devices were synthesized by the condensation of diaminomaleonitrile and 2,5-diamino-3,6-dicyanopyrazine with arylaldehydes. Substituent effects on their absorption and fluorescence spectra in the solution were determined by comparison with the parent chromophoric system. Their solid state absorption and fluorescence properties were evaluated with respect to their optimized molecular structures obtained by MOPAC methods.

Syntheses and fluorescent properties of 2,5-diamino-3,6-dicyanopyrazine dyes

Abstract 2,5-Diamino-3,6-dicyanopyrazine (2), a new fluorescent chromophore for functional dye materials, was synthesized by an oxidative coupling reaction of 2,3-diamino-3-(phenylthio)acrylonitrile (1). Compound 2 has a symmetrical structure and a strong intramolecular charge-transfer chromophoric system. It shows strong yellowish-green fluorescence in solution, and thus has good potential as a synthetic intermediate for fluorescent dye chromophores. Alkylation of the amino groups of 2 produced a bathochromic shift of λmax and resulted in red fluorescence in high quantum yield. On the contrary, acylation of the amino groups produced a hypsochromic shift of λmax, with blue fluorescence in high quantum yield. Modifications of the amino and cyano groups in 2 were studied in detail and many new fluorescent dyes were obtained. The absorption and fluorescent properties, together with fluorescence quantum yield of the substituted amino-3,6-dicyanopyrazines were correlated with their chemical structures.

Syntheses and properties of new styryl dyes derived from 2,3-dicyano-5-methylpyrazines

Abstract Reaction of 2,3-dicyano-5-methylpyrazine derivatives ( 3a-e ) with arylaldehydes gave new fluorescent styryl dyes ( 4–8 ). These styryl dyes have extended π-conjugated systems and are strong intramolecular charge-transfer chromophoric systems. They are of interest as non-linear optical materials, which should produce a large dipole moment in the excited state, and consequently induce large dipole moment differences accompanying laser irradiation. The styryl dyes derived from 2,3-dicyano-6-hydroxy-5-methylpyrazine showed large solvatochromism, depending on the polarity of the solvent, due to tautomerism between the hydroxypyrazine and the pyridone forms. The fluorescence and solvatochromism properties of dyes 4–8 were also studied, and structure-property relationships in solution and in the solid state were evaluated on the basis of molecular stacking in the solid state.

Syntheses and some properties of infrared-absorbing croconium and related dyes

Abstract The correlations between the structure and some properties of croconium and related cyanine dyes are discussed. It is shown by PPP MO calculations that the croconium dyes have the same chromophoric system as cyanines. The λ max of the croconium dyes undergoes a bathochromic shift of about 120 nm compared with the corresponding cyanine dyes. This shift can be calculated by the PPP MO method. Negative solvatochromism is observed for croconium dyes. Croconium dyes generally have better solubility than squarylium dyes in organic solvents and have good lightfastness in solvents, greatly improved by adding nickel complex as a stabilizer.

Self-assembling of aminopyrazine fluorescent dyes and their solid state spectra, Part 2

2,5-Diamino-3,6-dicyanopyrazine has strong yellowish-green fluorescence in spite of its small chromophoric system. Substitution at the amino groups, and hydrolysis followed by esterification of the cyano groups gave many types of fluorescent dyes. Their absorption and fluorescent spectra both in solution and solid state were correlated with their molecular stacking on vapor deposited thin film. Steric hindrances of the substitutents largely affected their solid state absorption and fluorescent spectra. Structural optimization by means of MOPAC PM3 method was conducted, and these results well indicated their molecular stacking behaviors.

Syntheses and characterization of new styryl fluorescent dyes from DAMN. Part II

Abstract 2,3-Bis(bromomethyl)-5,6-dicyanopyrazine ( 3 ) can be prepared more readily by the condensation of DAMN ( 1 ) and 1,4-dibromobutane-2,3-dione ( 2 ) than by direct bromination of 2,3-dimethyl-5,6-dicyanopyrazine. The Wittig reaction of 3 with arylaldehydes gave a new type of fluorescent styryl dyes ( 6–8 ). These styryl dyes have extended π-conjugation systems and strong intramolecular charge-transfer chromophoric systems. They have strong fluorescence in solution and some have fluorescence even in the solid state, which is very important to evaluate their electroluminescence (EL) property as the emitter for EL devices. Calculation of excitation energies using the PPP-MO method, and optimization of their structures using the MOPAC with the PM 3 method were conducted, and their spectral properties are discussed to correlate their functionalities with chemical structures.

Novel syntheses of anthraquinonoid near-infrared absorbing dyes

Abstract New series ofanthraquinonoid near-infrared absorbing dyes (hereinafter referred to as infrared dyes) for optical recording media were synthesised by the ring-closure reaction between 2,3-dibromoquinizarins and potassium 2-aminobenzenethiolate. These dyes absorb near-infrared light at 700–810 nm. It was found that substitution of electron-accepting groups, such as tetrahalogeno or the dicarboximide residue, on the quinizarin residue produces a large bathochromic shift of 40–100 nm, and that of the electron-donating alkoxy group at the 5-position of the thiol also produces a bathochromic shift of 25–40 nm.