Environment-friendly and high-performance azo dye substitutes for enhanced optical characteristics and color fastness: Design and screening, risk assessment and mechanism analysis

Abstract

Azo Dyes (ADs) are one of the most widely used dyes as they are characterized by high molar extinction coefficient and color fastness. However, it is difficult to remove them from the environment because of their stable structure. One of the bottlenecks in this field is to design environment-friendly and high-performance AD substitutes. Disperse Blue 79, which is commonly used in the dye industry, has been used as a target molecule for designing AD substitutes. A total of 27 substitutes with higher comprehensive effect value of molar extinction coefficient and color fastness (amplification > 20 %) were designed. After the assessment of environmental characteristics, stability and human health risk using the 3D-QSAR, molecular docking, density functional theory (DFT), and toxicokinetic techniques, the Derivative-47 was screened out. The synthetic possibility and characteristic enhancement mechanism of Derivative-47 were calculated using DFT and time-dependent density functional theory (TDDFT). Results showed the designed substitutes could be potentially synthesized in real environment (Gibbs free energy = −122.37 a.u < 0). The change in MO pairs, orbital transition and the electron transfer characteristics between the ground and excited states were the main reasons for the enhancement of molar extinction coefficient. Moreover, the increased color fastness could be primarily related to the reaction intensity of nucleophilic reaction site and the ability of molecules to lose electrons. This study aims to establish a system that integrates design, selection, and evaluation processes, provides new insights for the design of environment-friendly AD substitutes with higher molar extinction coefficient and color fastness.