Quantification of molecular orbitals based on projection operators: methodological development and applications to basicity prediction of organic compounds in the gas phase

Abstract

Basicity is an important parameter with impact on biological systems and technological problems. The HOMO-LUMO and FERMO theoretical approaches can describe the acid-base behavior of compounds as amines, carboxylic acids and alcohols. In this work, a method was developed using the localization degree ГFERMO parameter based on projection operators to quantify the localization of molecular orbitals. This new method was employed for the analysis of the protonation reaction of 30 organic compounds. The quantitative data from our findings were able to reproduce experimental data, pointing out that the FERMO approach could better describe the acid-base behavior of the investigated compounds.