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

Abstract

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 (Kb) for binding of a series of radical anions from para- and ortho-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(-)(r).

Site-Specific Description of the Enhanced Recognition Between Electrogenerated Nitrobenzene Anions and Dihomooxacalix[4]arene Bidentate Ureas

“…This approach has proven useful for comparing binding abilities between structurally different anions. [17][18][19][20] The knowledge of the molecular features of the receptors has been focused. For example, Gale and co-workers 21 have reported that the acidity of the NH group of some mono-thioureas directs the anion recognition and mathematical models could predict the transmembrane transport ability.…”

Role of Reaction Conditions in the Global and Local Two Parabolas Charge Transfer Model

“…Our last application of the model is in a supramolecular chemistry problem concerned with electrochemically controlled hydrogen bonding (ECHB), which has potential interest in applications such as chemical sensors, molecular electronics, and molecular machines. , In ECHB electronic transfer is used to modify the strength of H-bonds, for example, by reducing a chemical moiety one can increase the negative charge on the H-accepting atom with the concomitant effect of strengthening the H-bond. It is recognized that in nitrobenzenes the nitro groups are usually weak H-acceptors in solution, due to the low polarity of the N–O bond.…”

“…It is recognized that in nitrobenzenes the nitro groups are usually weak H-acceptors in solution, due to the low polarity of the N–O bond. However, the reduction of nitrobenzene increases the negative charge on the oxygen atoms and strengthens the H-bonding with an H-donating guest. , Recently, Martı́nez-González et al studied the substituent effect on reduced nitrobenzenes (ortho- and para-substituted) interacting with 1,3-diethylurea (13du) as H-donating guest. They determined the binding constants ( K b ) that properly describe the reactivity trends.…”

“…These expressions distinguish the donating and accepting charge process, and partially incorporate the requirements of the ensemble theorem. Following the procedure leading to the definition of electrophilicity, GCV introduced the electrodonating, ω – = (μ – ) 2 /2η, and electroaccepting, ω + = (μ + ) 2 /2η, powers, global reactivity descriptors that have been applied and commented in the literature. − …”

Electrochemical behavior of 1,2-dihydroxyanthraquinone dianion in aprotic solvents-DMSO and DMF: understanding the hydrogen bonding phenomena and protonation effect in biochemical systems

“…The latter is more sensitive for H-bonding interactions [34]. In electrochemistry especially cyclic voltammetry is used to measure the hydrogen bonding interaction, this is due to the electrostatic properties of hydrogen bonds [35].…”