Concerning the FERMO concept and Pearson's Hard and Soft acid-base principle

Abstract

O conceito FERMO foi empregado com sucesso ao princípio ácido-base de dureza e moleza de Pearson para quatro ligantes ambidentados. Usando um postulado intuitivo basedo em argumentos HOMO-LUMO para a dureza e moleza, as diferenças de energia FERMO-LUMO descrevem corretamente os sítios duros e moles para os sistemas estudados. Além disso, os orbitais de Kohn-Sham e Hartree-Fock levam às mesmas conclusões. The FERMO concept was successfully applied to the Pearson´s Hard and Soft acid-base principle for four ambidentate ligands. Using an intuitive statement based on the HOMO-LUMO approach to the hardness and softness, the FERMO-LUMO gaps correctly describe the soft and hard sites in the studied systems. Moreover, Kohn-Sham and Hartree-Fock MOs lead to same conclusions.

The role of the Frontier orbitals in acid–base chemistry of organic amines probed by ab initio and chemometric techniques

“…and (2) Would HOMO be the best orbital to describe the reaction? To find the answer for these questions, we have used a new chemically intuitive FERMO concept to describe the acid/base behavior [21][22][23][24][25]. It has been shown elsewhere that the FERMO idea may be an alternative way to explain chemical phenomena when HOMO-LUMO arguments fail or cannot be applied.…”

“…The orbital composition is also an important indicator for discovering the adequate orbital [21,22]. The MO shape and the atomic composition are very important parameters for analyzing FERMO [23,24].…”

“…Furthermore, it is important to note that the FERMO concept leads to same conclusions about chemical reactivity for both HF and Kohn-Sham approaches [21][22][23][24]. Nowadays, it is well-known that the Kohn-Sham DFT is a leading method for electronic structure calculations in chemistry mainly due to its high efficiency and relatively low computational cost [19,33].…”

“…In line with that our theoretical results using B3LYP combined with the FERMO concept could be justified. In these cases, the respective errors for the constituents of the reaction cancel, as electrons are localized for all reactants and the product [21][22][23][24][25].…”

“…This concept can be understood as a complement to the HOMO-LUMO argument. Another important feature in FERMO is that both HF and Kohn-Sham orbitals make the same conclusions about reactivity [21][22][23][24]. A careful study is necessary to understand when the use of HOMO energy works or not.…”