Investigation of ground state tautomeric form of a heterocyclic disazo dye derived from barbituric acid by ab initio Hartree–Fock and density functional theory calculations

Abstract

The optimized molecular structures, vibrational frequencies and corresponding vibrational assignments of 10 tautomeric forms of a heterocyclic disazo dye [5-(3-methyl-4-phenylazo-1H-pyrazole-5-ylazo) barbituric acid] have been calculated using ab initio Hartree–Fock (HF) and density functional theory (B3LYP) methods with 6-31G(d, p) basis set level. Calculations have shown that the most probably preferential form of the heterocyclic disazo barbituric acid dye in the ground state is azo-hydrazo-keto form corresponding to the experimental results.