Synthesis of phthalimide disperse dyes and study on the interaction energy

Three azo dyes had been synthesized using N-ethyl substituted, dibromo-substituted and dicyano-substituted phthalimides as diazo components. All of the synthesized intermediates and dyes have been characterized by MS, 1H NMR, IR and elemental analyses. The dyeing behavior and fastness properties of these dyes have been investigated. Modeling the interaction energy of benzene-benzene, phthalimide-benzene and phthalimide-phthalimide rings, molecule optimization and the interaction energy researching have been done with density functional theory ωB97XD, 6-311G++(d,p) basis set. The results showed that: phthalimide molecule has better coplanarity. Molecule energy of benzene-benzene, phthalimide-benzene and phthalimide-phthalimide rings decreased first and then increased with the increase of the distance between the rings, the lowest energy happened when the distance was about 3.5 Å. Electrostatic force affected the interaction energy most. Substituent groups mainly altered the dispersion force and reduced the energy of the system. The optimization interaction energy of phthalimide-phthalimide, phthalimide-benzene and benzene-benzene was −47.78 kJ/mol, −34.66 kJ/mol and −17.59 kJ/mol. Substituted dibromo group reduced the dipole interaction of the dye.