Study on the dissociation properties and spectra of iodobenzene under external electric field

In accordance with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) method, the characteristics of iodobenzene (C6H5I) under the impact of various external electric field (EEF) (0 V center dot nm-1 similar to 10.28 V center dot nm-1) are calculated, using B3LYP/LanL2DZ group. As evident from the computational results, an escalation in EEF corresponds to a decrease in total energy, an increase in dipole moment, elongation of the 6C-12I bond, contraction of the 2C-7H bond, and a reduction in the energy gap. With an increase in EEF, there is an observed enhancement in the intensity of infrared spectral characteristic peaks associated with the stretching and bending vibrations of the 6C-12I bond; The Raman spectral characteristic peak corresponding to the 6C-12I bond experiences a redshift. When EEF increases, the single point energy decreases first and then increases. The barrier almost disappears when EEF reaches 16.46 V center dot nm-1. Furthermore, as EEF attains higher magnitudes, the excitation energy of the first nine excited states experiences a reduction and the oscillator strength changes. Examining the impact of EEF on the characteristics and spectra not only offers a theoretical foundation for understanding the dissociation of iodobenzene but also provides valuable insights for the development of detection methods for other organic pollutants.