Modem reprographics

The syntheses, photophysical properties and pH-sensitive studies of heterocyclic azo dyes bearing coumarin-thiophene-thiazole

This study reports the synthesis of two novel thiazolylazo dyes (4 and 5) bearing coumarin-thiophene moiety. UV-Vis spectroscopy was used to investigate the photophysical properties of 4 and 5 in different solvents. The dyes displayed good potential for hydroxide sensing in different mediums. The reversibility was also studied, and it was found that 4 and 5 could be reverted to their original state by adding acid. Furthermore, the acidochromic properties were studied in protic and aprotic media. Both dyes displayed a good acidochromic response in DCM. Moreover, 4 and 5 were investigated for pH sensing, and it was found that both compounds displayed changes in absorption spectra in a basic media. The theoretical calculations were carried out to investigate the deprotonation and protonation mechanisms using density functional theory (DFT). The thermal properties of the dyes were investigated using thermogravimetric analysis (TGA). The results showed good thermal stability up to around 200 °C.

Classifications, properties, recent synthesis and applications of azo dyes

In this work, we have presented a very detailed review of the different classification of azo dyes as a function of the number of azo groups and the appropriate functional groups. Then we pointed out some chemical properties of these dyes such as reactivity, isomerization and tautomerism and listed. In the following, we have summarized some recent syntheses of azo dyes and the mechanism of azo dye/polymer conjugation. Finally, we indicate the principle of Gewald's reaction and its application to the synthesis of new azo dyes.

Synthesis and spectroscopic properties of new azo dyes derived from 3-ethylthio-5-cyanomethyl-4-phenyl-1,2,4-triazole

New 1,2,4-triazole colorants were obtained, in high yields, by coupling 3-ethylthio-5-cyanomethyl-4-phenyl-1,2,4-triazole (1) with diazotized aniline derivatives 2, 4 and 6. The azo dyes prepared in this work may exist in three tautomeric forms. We found that the tautomerism is influenced mainly by the nature of substituent at the para position of the aniline coupling component. This tautomerisation was observed in the NMR spectra of the dyes. The dyes were characterized by IR, ¹H-NMR, ¹³C-NMR and MS spectroscopic techniques.

The Effect of Crystal Properties on the Manufacture and Application Performance of Copper Phthalocyanine Pigments

Copper phthalocyanines are commercially important organic pigments for blue shades of colour. They are dispersed by mechanical means as tiny molecular crystals (of dimensions 0.02—0.5 μm) into a wide range of commercial media to form products such as printing inks, paints and coloured plastics. Many important technological properties of copper phthalocyanine pigments, including colour strength and dispersion performance, depend on the physical properties of their crystals, notably crystal lattice type, crystal size and crystal shape. The roles which these crystal properties play in determining a copper phthalocyanine pigment's technological performance are briefly reviewed. The reduction of crystal aggregation during the manufacture of a copper phthalocyanine pigment and the control of flocculation in an application medium are also highlighted.