Interaction of N,N´-substituted diimides of binaphthylhexacarboxylic acid with sodium dithionite in aqueous-alkaline acid solution

The article presents the details about the interaction of a number of N,N´-substituted diimides of binaphthylhexacarboxylic acid (cubogenes) with sodium dithionite. The reaction takes place in the formation of perylene dyes in the technology of dyeing and printing of cotton fabrics. The authors found that there is a rapid formation of intermediate products - tetraanions of initial compounds due to the transfer of two electrons from dithionite anions in the initial stage of the reaction. Subsequently, these intermediates can be transformed into the initial dianions by oxidation either by air oxygen or by sulfite formed by dithionite at the first stage. Also, a parallel chemical stage of cyclisation with the formation of perylene derivatives is possible depending on the nature of substituents at nitrogen atoms in the initial diimide molecules. The occurrence of a reversible redox stage of tetraanion formation confirmed electrochemically on a carbon-titanium electrode. The elemental analysis of IR and electronic absorption spectroscopy show the formation of perylene derivatives. The authors proposed a general stoichiometric reaction mechanism for the interaction reactions of cubogens having different substituents at nitrogen atoms with sodium dithionite on the basis of the experimental data. The results are applicable in the practice of finishing textile materials with cubogenes and in liquid-phase preparation of thin-layer photoactive materials based on perylene derivatives.