Ultrasonic, spectrophotometric and theoretical studies of sigma and PI interactions of iodine with substituted benzene

Abstract

The charge transfer (CT) interaction between three structurally different benzenoid compounds (donors), namely, chlorobenzene (1), phenol (2), anisole (3), and iodine (I₂, acceptor) were investigated by experimental methods (ultrasonic and UV-Visible analysis) and theoretical calculations. Notably, strong solute–solute interactions and the existence of a CT type of interaction between 1–3 and I₂ is clearly analyzed from the trend in acoustical and excess thermo acoustical parameters with concentration at 303 K in an n-hexane medium. The formation of 1 : 1 complexes between iodine and 1–3 was established by the UV-visible spectroscopic method. The structure and stabilization energies of 1–3 and I₂ were further calculated by DFT calculations. Among the σ- and π-type interactions, a π-type complex (1a–3a) with an atom-centered orientation is found to be the preferred and stable geometry for all the CT complexes. The stability constant of the CT complexes was calculated by spectroscopic and ultrasonic methods, which show a similar trend with the DFT computed stabilization energies. Furthermore, AIM and NBO analyses were used to quantify the nature of the stabilizing interactions that exist in 1–3 and the I₂ CT complexes. Our computed results are in good agreement with the experimental observations.