Factors influencing the thermal stability of azo and bisazo compounds

The present study investigates the effects of substituents, structural rigidity, tautomerism, hydrogen bonding interaction, and spatial hindrance on the thermal stability of some azo compounds including bisazo Tröger base analogs (BATBAs). The relatively large structures of BATBAs allow assessing their thermal stability before reaching the sublimation or boiling point. BATBAs carry two identical azo groups per molecule resulting in an intense and detectable sign of decomposition. Unlike most azo dyes, BATBAs are not ionic and prevent the complexity of decomposition associated with simultaneous dehydration. A few commercial azo dyes are also analyzed to evaluate the generality of the conclusion. Graphic abstract: