The synthesis, colour, and constitution of methine dyes formed by condensation of benzaldehydes and nitrosobenzenes with dicyanovinyl analogues of indane-lr3-dione have been investigated. 3-Dicyanovinylindan-1 -one (3) and lr3-bisdicyanovinylindane (5) give magenta (hmax. ca. 560 nm) and blue (Amax, ca. 600 nm) dyes respectively with 4-dialkylaminobenzaldehydes. Aza analogues formed from (3) and ( 5) and 4-dialkylaminonitrosobenzenes are significantly more bathochromic, and the exceptional shift in the case of dyes formed from (5) (ca. 150 nm) permits the synthesis of a new class of dyes absorbing in the near-i.r. region, with absorption maxima in the range 700-850 nm.

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The first examples of monoazo dyes absorbing in the near infrared (up to 806 nm in dimethyl sulphoxide) have been prepared from 2-(4-amino-2-acetylaminophenylazo)-4-chloro-5-formylthiazoles by condensing the formyl group with suitably electronegative active methylene compounds under base catalysed conditions.

The nanophotocatalytic process using semiconducting oxides with a nanostructure is one of the technologies used for the destructive oxidation of organic compounds such as dyes. The photocatalytic oxidation of a textile dye-C. I. Basic Blue 41 (BB41) in aqueous solution was assessed by UV ray irradiation in the presence of TiO 2 nanoparticles. The effect of initial dye concentration, pH and TiO 2 loading were investigated and the optimized conditions for maximum amount of degradation were determined. Analysis of the kinetics showed pseudo-first-order model. The mineralization of the dye was reported by measuring the initial and final chemical oxygen demand of the solution that was irradiated under optimized conditions.

The synthesis of a series of 3-(p-substituted phenylazo)-6-pyridone dyes which is suitable for the dyeing of polyester fabrics, is described. Visible absorption spectra of the dyes were examined in various solvents and the compounds in solution exhibited hydrazone-common anion equilibrium. The electronic absorption spectra cover a λ max range of 404-464 nm in DMF at uniformly high absorption intensity between 5.33 × 10 4-8.55 × 10 4 l•mol-1 •cm-1 and gave bright intense hues of yellow to orange on polyester fabrics. The colour parameters of the dyed fabrics were measured and the dyes have excellent exhaustion between 72%-79% for polyester fabrics, more intense and of very good fastness properties on polyester fabrics. The remarkable degree of levelness and brightness after washing is indicative of good penetration and excellent affinity of these dyes for the polyester fabric.