Modeling continuous changes in substituent electronegativity and chemical hardness using fictitious nuclear potentials

摘要

Electronegativity and chemical hardness are important conceptual tools in organic and organometallic chemistry. Computational chemistry can aid understanding of these concepts by simulating fictitious substituents with smoothly varying electronegativity and chemical hardness. This work shows that Gaussian smearing of an atom's nuclear charge distribution enables variation of its electronegativity and chemical hardness, without changing the total molecule charge. Tunable covalent, Lewis acid, and Lewis base substituents give chemically reasonable results in several canonical chemical reactions. These include hard-soft acid-base effects on thiocyanate and enolate isomerization, ligand trans influences on the stability of organometallic complexes and the thermodynamics of reductive elimination, and substituent effects on the proton affinities of benzene derivatives. The results illustrate the utility of these fictitious substituents and motivate their use as interpretive tools.