Effect of solvents, substituents and pH on the electronic spectra of some heterocyclic azo compounds

The electronic spectra of some axo compounds of 5-amino-4-arylazo-3-methyl- 1-phenylpyrazoles have been studied and the different bands observed have b een assigned to various electronic transitions. The solvatochromic behavior of these compounds has been. investigated by studying their visible spectr a in. various organic solvents of different polarities as well as in buffer solutions. The basicity constants (pK(BH)(+)) of the different compounds w ere determined from the spectra of the compounds in aqueous-ethanolic solut ions of varying pH values. The effect of concentration of the compounds in ethanol and dimethylformamide DMF solutions has been also investigated. Cor relations between, v (cm(-1)) (main frequency for each compound) with the s olvent parameters beta and pi* have been also made.