The Eriochrome Blue Black (EBB) azo dyes have attracted special
interest in various applications as well, such as metal chelates for
dyeing protein [18], chromogenic indicator [19], and dye location
characterization in surfactant micelles [20] and probe molecules
to characterize catalysts [21,22].
The characterization and the understanding of tautomerization
mechanism are crucial for controlling the molecular properties
depending on the polarity and pH of the medium. In view of the
above observations, we thought it is worthwhile to study the spec-
tral behavior of an azo dye involving the naphthalene moiety in
pure and series of mixed organic solvents in various polarities. In
this study, we focused on the objective to assess the impact of the
effects of pH-, dye concentration-, solvent-, temperature-, and
time-dependences on the UV–vis. spectra of Eriochrome Blue Black
B (EBB) azo dye. In addition, some electronic structure properties of
tautomeric forms were investigated by using DFT quantum chemi-
cal calculations in order to give more insight into the azo-hydra-
zone tautomerism and to confirm the experimental findings.
2. Experimental