The azo compounds are among the largest group of dyes with
over one thousand compounds being commercially offered. These
dyes show considerable activity in high-tech applications
especially in the electronics and nonimpact printing industries.
They are also extensively used for dyeing fabrics and coloring agents in inks. In last two decades, there is a rapidly growing
interest in the potential of their biochemical applications [1–3]
and in their use for optical data storage [4–7]. The applications of
these dyes are strongly depended on their photophysical proper-
ties. For instance, photophysical properties of azo-hydrazone tau-
tomerism have been used to some extent for dye location
characterization in surfactant micelles and textile fibers [8–10],
photographic systems [11], dyeing [12], bleaching [13–15] and
polymers [16,17].