ible spectra in
ethanol (Fig. 2a) and in methylene chloride (Fig. 2b). The correlation
between the structural formulae of these dyes and the absorption
spectral data is given in Table 1 . The electronic transition n–*
(ε ≈ 103 L mol−1 cm−1 , max ≈ 330–439 nm) generally occurs in
amide carbonyl in dyes I–III together with that occurs in NO2 group
in dye IV and –* electronic transition (ε ≈ 104 L mol−1 cm−1 ,
max ≈ 230–260 nm) occurs in azo group/and or other unsaturated
bonds in all dyes (I–IV).