Azo compounds containing heterocyclic moieties have drawn the attention of many researchers , , ,  and . It has been well established that the use of heterocyclic amines with oxygen as the π-excessive hetero uk101 as diazo component has a marked bathochromic effect compared to analogous dyes derived from benzenoid compounds . Azo derivatives containing antipyrine moiety have many advantages including color depending effect as an intrinsic property leading to better dye ability. The color of these azo derivatives depends on the nature of both the diazo and the coupling components. Majority of the azo compounds are derived from the coupling of diazotized heterocyclic amines with aromatic hydroxyl and amino compounds. The position of azo and hydroxyl groups in these molecules brings into play the azo-hydrazone equilibrium . The use of protein–ligand docking has become a standard method in potentiometric studies. The protein groups surrounding the ligand can highly influence the local pH, so that a different protonation could be favored in the bound state. To account for this effect, the ideal case would be to use multiple protonations in the docking and have the algorithm automatically pick the correct state. Molecular docking is widely used to predict protein–ligand  and  and to screen large libraries for molecules that will modulate the activity of a biological receptor.