Employment of Electrodonating Capacity as an Index of Reactive Modulation by Substituent Effects: Application for Electron-Transfer-Controlled Hydrogen Bonding

Evaluation of the substituent effect in reaction series is an issue of interest, as it is fundamental for controlling chemical reactivity in molecules. Within the framework of density functional theory, employment of the chemical potential, μ, and the chemical hardness, η, leads to the calculation of properties of common use, such as the electrodonating (ω^–) and electroaccepting (ω⁺) powers, in many chemical systems. In order to examine the predictive character of the substituent effect by these indexes, a comparison between these and experimental binding constants (<i>K</i>_b) for binding of a series of radical anions from <i>para</i>- and <i>ortho</i>-substituted nitrobenzenes with 1,3-diethylurea in acetonitrile was performed, and fair correlations were obtained; furthermore, this strategy was suitable for all of the studied compounds, even those for which empirical approximations, such as Hammett’s model, are not valid. Visual representations of substituent effects are presented by considering the local electrodonating power ω^–(<i><b>r</b></i>)