Molecular Structure and Spectroscopic Studies of Some Diazo Dyes Compounds using DFT Method

Diazo dyes compounds have a variety biological and industrial applications. In this study, the molecular structures and the spectroscopic parameters of three synthesized diazo dyes 1–3 were computed using a Density Functional Theory DFT method with the B3LYP/6-311++G(d.p), The results indicate that all three diazo dyes are preferred thermodynamically. Compound 3 has a higher value of entropy and more negative values of heat formation and Gibb's free energy as compared to the other dyes. The FTIR spectra of 2 and 3 show that the nitro functional groups at ortho positions appear at lower symmetrical stretching frequencies. At all, there is a good agreement with the experimental results. On the other hand, the energy gap decreases in this order 2, 3 and 1, also, the FTIR spectrum of compound 1 shows a lower symmetrical stretching frequency of the nitro functional group at the para position.