Determination of the best functional and basis sets for optimization of the structure of hypervalent iodines and calculation of their first and second bond dissociation enthalpies

Abstract

Hypervalent iodines are widely used in organic chemistry, and their most important feature is the three-center four-electron bond. However, there have been few reports on the measurement of their bond dissociation enthalpy (BDE). Therefore, in many cases, BDE is estimated by computational calculations. However, the value of a calculated BDE usually varies depending on the choice of functional and basis set, and the best method for making an accurate evaluation of the three-center four-electron bond has not been determined. We succeeded in determining the best functional and basis set to calculate the three-center four-electron bond to within 0.79% error and 0.53 standard deviation. Using the optimal functional and basis set, the first and second BDEs of several hypervalent iodines are calculated, and as the effect of benzene substituents was investigated, negative correlation was observed in the Hammett plot. In addition, the effect of ortho-substituent in cyclic hypervalent iodine was found to be significant. Furthermore, the decomposition route of hypervalent iodine is calculated. The value of a calculated BDE usually varies depending on the choice of functional and basis set. We succeeded in determining the best functional and basis sets to calculate the three-center four-electron bond of hypervalent iodine to within 0.79% error and 0.53 standard deviation. Using the optimal functional and basis sets, the first and second BDEs of several hypervalent iodines are calculated, and additionally, the decomposition route of hypervalent iodine is calculated.