Cheol Jun Song

Synthesis and spectral characterisation of dicyanopyrazine-related cyanoheterocycles

Four dicyanopyrazine-related cyanoheterocycles have been synthesised and characterised; they show different absorption maxima values and molar absorptivity in absorption spectra. HOMO and LUMO energy levels have been obtained by electrochemical measurements and DMol3 calculation and show little difference in HOMO values but big differences in LUMO values. Their UV-Vis absorbance and fluorescence spectra have been investigated in chloroform and toluene and their aggregation decreases as the concentration decreases in toluene.

Synthesis and photophysical properties of silicon(IV) tetrapyrazinoporphyrazines axially substituted with ethylene glycol chains as potential photosensitizer

Photodynamic therapy involves administration of a tumor-localizing photosensitizer, which may require metabolic conversion, followed by activation of the photosensitizer with light of a specific wavelength. In this paper, we report the design and synthesis of silicon(IV) tetrapyrazinoporphyrazines derived from 5,9,9-trimethyl-5,6,7,8-tetrahydro-5,8-methanoquinoxaline-2,3-dicarbonitrile. The HO–(CH2CH2O)n–CH3 groups were introduced at axial positions to give a specific functionality. In particular, poly(ethylene glycol) groups were expected to increase water solubility without changing the λmax.

Synthesis and Characterization of Modified Dyes for Dye-Based LCD Color Filters

Color filters (CFs) are important elements for making color images in liquid crystal displays (LCDs) and other imaging devices. A colored layer is fabricated with colorants of red, green, and blue from either dyes or pigments. These colorants are arranged uniformly and make up the CF while also converting white backlight into a color image. The pigment is advanced to thermal stability, light resistance and chemical resistance, so many used for manufacturing color filters. However, the color filters manufactured with pigments have spectral drawbacks such as decreased transmittance of light and decreased contrast ratio both caused by aggregation of pigment particles. Thus, it is necessary to do the expensive and time-consuming dispersion process for obtaining stable and finer pigment millbases without molecular aggregation. In this study, our focus was on a new series of acid dye systems that have alkyl amine groups because it has an advantage in solubility of organic solvents. As a result of our focus, we have designed and synthesized new acid dyes that consist of alkyl amine groups, using a simple method of reaction. In addition, manufacturing color filters without the milling process in the optical characteristics, thermal, chemical stability were investigated.

Synthesis and spectral properties of tetraquinoxalino-porphyrazines containing benzocrown-ether group

The synthesis and spectral properties of the metal-free and the Mg complex derivatives of crown-substituted tetraquinoxalinoporphyrazine are described. Porphyrazine 4 and 5 have satisfactory solubility in chlorinated hydrocarbons, THF and toluene, but are practically insoluble in alcohols. Porphyrazine 5 generally did not show aggregation in CHCl3 but aggregate in DMF.

Red-emitting materials derived from 2,3-dicyanopyrazine for organic light emitting devices

Styryl-substituted derivatives of 2,3-dicyanopyrazine were designed and synthesised by the Knoevenagel condensation of 2,3-dicyano-5-methylpyrazines with 4-(diphenylamino)benzaldehyde for use as red-emitting fluorescent dyes in organic light-emitting devices. Structural analysis of the red-emitting styryl fluorescent dyes was carried out using 1H NMR, FT-IR, and elemental analysis. The electroluminescent performance of multi-layered organic light-emitting devices fabricated with the triphenylamine-substituted dicyanopyrazine compound as the emitting layer achieved a current efficiency of 1.57 cd A-1 in the green region with CIE coordinates of (0.37, 0.51). However, the green emission (525 nm) observed from the tris-(8-hydroxyquinolinato)aluminum(III) (Alq3) electron-transport layer indicated the action of a recombination phenomenon between the emitting layer and the Alq3 electron-transport layer. The device fabricated with the tert-butylphenyl-substituted compound achieved a current efficiency of 0.238 cd A-1 in the red region with CIE coordinates of (0.54, 0.42) and showed no recombination phenomenon.

Optical Sensitivity of Electrospun Fibers Containing Quinoxalines Derived with Metal Ion Chelating Agent

Fluorescent chromophores are generally known to have planar and rigid -conjugation systems, and we have been interested in the chemistry of nitrogen-containing heterocyclic molecules for many years. Quinoxaline was the representative fluorophore, and several quinoxaline derivative compounds were reported over the recent years. Quinoxaline can easily change their absorption or emission wavelength by oxidation among proton and nitrogen of the quinoxaline ring. In addition, it has been proved that many types of metal chelating ligand substituents such as dipyrrole, terpyridine, and crown-ether rings can control electronic levels of those fluorephores. In this study, we designed and synthesized several 2,3-distyrylquinoxaline derivatives with each have a substituent of alkyl groups which have different electron-donating abilities and aza-crown ether, a chelating agent with metal-cation. The chromophoric system of these compounds, and the substituent effects on their absorption spectra in a solution, were studied. And we approached the application to nanofibers by electrospinning which contained the synthesized colorants mentioned above