Tautomerism in some dihalophenolindophenol dyes – A DFT study

Indophenol is a deep blue dye (the group with various substituents). It is found in many dyes used in hair coloring and textile, and found applicability as lubricants, redox materials, liquid crystal displays, etc. A variant of it, dichlorophenol-indophenol, is often used to determine the presence of vitamin C. Indophenol and its derivatives may exhibit resonance-assisted proton tautomerism. In the present study some of those types of tautomers have been investigated within the constraints of density functional theory (DFT) at the level of B3LYP/6-311++G(d,p). All the species presently considered (in vacuum conditions) have not only exothermic heat of formation values but also possess favorable Gibbs free energy of formation values and they are electronically stable. Various structural and quantum chemical data have been collected and discussed including IR and UV-VIS spectra.