Computational modelling of the influence of substituent effects on phthalimidylazo disperse dye hydrolysis and interaction energy

Abstract

Six azo dyes have been synthesised using N-substituted phthalimides as diazo components. Substitution effects on dye hydrolysis and intermolecular interactions were investigated with density functional theory (DFT) at B3LYP/6-311G level. The results showed that the phthalimide moieties adopted a coplanar conformation in respect of the azo-coupled phenyl rings in all six dyes. N-Alkyl substitution had little influence on the absorption maxima. Bromo and cyano substitution on the phthalimide ring resulted in hypsochromic and bathochromic shifts of the absorption maxima respectively. Hydrolysis of the phthalimide ring was found to be largely influenced by steric effects rather than inductive effects of substituents. It was also found that p-stacking interactions of phthalimide/phenyl and phthalimide/phthalimide dimers were promoted by substituents. The results indicated that interactions are dominated by electrostatic and even more importantly dispersion forces. The computational results were also confirmed experimentally. Coloration Technology Society of Dyers and Colourists

A feasible approach for enhancing union dyeing of wool/acrylic blend fabrics with heterobifunctional cationic reactive dyes

“…As in Dye 1, the cationic group located in the diazo component showed good coplanarity with the chromogen of the dye structure, which was beneficial for the formation of electrostatic attraction between the cationic reactive dyes and acrylic fiber, leading to higher exhaustion on acrylic fabrics. 20

Figure 4.The interaction between two kind of fibers and the cationic reactive dye.

Figure 5.Effect of dyeing pH on (a) the exhaustion of cationic reactive dyes on wool and acrylic fabrics and (b) union dyeing of cationic reactive dyes on wool and acrylic fabrics.

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