Evaluation of the structural properties of powerful pesticide dieldrin in different media and their complete vibrational assignment

Abstract Dieldrin was characterized by using Fourier Transform infrared (FT-IR) and Raman (FT-Raman), Ultraviolet–Visible (UV–Visible) spectroscopies. The structural and vibrational properties for dieldrin in gas phase and in aqueous solution were computed combining those experimental spectra with hybrids B3LYP and WB97XD calculations by using the 6-31G* and 6-311++G** basis sets. Here, the experimental available Hydrogen and Carbon Nuclear Magnetic Resonance ( 1 H and 13 C NMR) for dieldrin were also used and compared with those predicted by calculations. The B3LYP/6-311++G** method generates the most stable structures while the results have demonstrated certain dependence of the volume and dipole moment values with the method, size of the basis set and, with the studied media. The lower solvation energy for dieldrin (−32.94 kJ/mol) is observed for the higher contraction volume (−2.4 A 3 ) by using the B3LYP/6-31G* method. The NBO studies suggest a high stability of dieldrin in gas phase by using the WB97XD/6-31G* method due to the n→π* and n*→π* interactions while the AIM analyses support this high stability by the C18⋯H26 and C14⋯O7 contacts. The different topological properties observed in the R5 ring suggest that probably this ring plays a very important role in the toxics properties of dieldrin. The frontier orbitals show that when dieldrin is compared with other toxics substances the reactivity increases in the following order: CO  6 Cl 6 − where evidently, the presence of five rings and six Cl atoms decrease the reactivity of dieldrin, as compared with hexachlorobencene. The WB97XD method and the two basis sets predicted for dieldrin in both media low reactivities, higher nucleophilicity and, low electrophilicity. All the bands observed in the IR and Raman spectra were completely assigned to the 75 vibration normal modes and their harmonic force fields and force constants for first time are reported for dieldrin. The predicted FTIR, FT-Raman, UV–Visible and 1 H and 13 C NMR spectra for dieldrin show a reasonable concordance with the experimental ones.