Density Functional Theory Study on the Van Der Waals and Basis Set Effect of Halogen Binding in Hypervalent Iodine Macrocycles

Previous computational work using density functional theory (DFT) on the hypervalent iodine macrocycle (HIM) system described by Pandey et. al. [J. Mater. Chem. C 13(2025)842] determined that B3LYP/6-31G(d,p)[LanL2DZ] was not a sufficient functional/basis set to describe the halogen binding between the iodine of the HIM monomer and bromine. In this study, we investigate the cause of the overly positive binding energy and propose other computational methods that give an accurate description, as well as investigating whether the consideration of Van Der Waals forces using Grimme’s D3 empirical dispersion model is significant. Using models of the HIM-Br system and a representative anionic iodine monobromide (I-Br) model, it is determined that including D3 dispersion has no significant effect on the binding energy or bond length of the system. Additionally, the necessity of basis sets that consider effective core potentials (ECPs) for the accurate description of the HIM system is confirmed. It is found that while using a full B3LYP/def2 (either triple- or quad-zeta) computation is accurate, there are much smaller one-parameter hybrid functionals such as mPW1PW91/3-21G* that serve as a quick method for qualitative or screening analysis.