Effect of substituent and solvent on cation–π interactions in benzene and borazine: a computational study

Abstract

A DFT and ab initio quantum chemical study has been carried out at different theoretical levels to delve into the role of the cation-π interaction within the main group metal cations (Li(+), Na(+) and K(+)), substituted benzene and borazine. The effects of electron withdrawing and electron donating groups on these non-covalent forces of interaction were also studied. The excellent correlation between Hammett constants and binding energy values indicates that the cation-π interaction is influenced by both inductive and resonance effects. Electron donating groups (EDG) such as -CH3 and -NH2 attached to benzene at the 1, 3 and 5 position and the three boron atoms of borazine were found to strengthen these interactions, while electron withdrawing groups (EWG) such as -NO2 did the reverse. These results were further substantiated by topological analysis using the quantum theory of atoms in molecules (QTAIM). The polarized continuum model (PCM) and the discrete solvation model were used to elucidate the effect of solvation on the cation-π interaction. The size of the cations and the nature of the substituents were found to influence the enthalpy and binding energy of the systems (or complex). In the gas phase, the cation-π interaction was found to be exothermic, whereas in the presence of a polar solvent the interaction was highly endothermic. Thermochemical analysis predicts the presence of thermodynamic driving forces for borazine and benzene substituted with EDG. DFT based reactivity descriptors, such as global hardness (η), chemical potential (μ) and the electrophilicity index (ω) were used to elucidate the effect of the substituent on the reactivity of the cation-π complexes.

Molecule Channels Directed by Cation‐Decorated Graphene Oxide Nanosheets and Their Application as Membrane Reactors

“…It is worth mentioning that, among the monovalent metal ions that we tested (Li + , Na + , and K + ), Li + was found to have no such effect, and even the original homogeneous GO suspension showed no change after the Li + ion was added at an equimolar ratio. This result occurred because, though a metal cation with a smaller ionic radius has a stronger ability to attract the π‐electron cloud of the benzene ring, its hydration energy in aqueous solution is also much higher than those that have a larger ionic radius. A higher hydration energy means that the metal cation can be highly solvated in aqueous solution and hence be surrounded by a large number of water molecules, which provide a strong shielding effect, preventing the metal ion from bonding with either the sp 2 clusters of the GO basal plane through cation–π interaction, or to the sp 3 matrix with oxygen‐containing functional groups by coordination.…”

Probing the selective separation of potassium ion from sodium ion with cyclopentadienyl anion as receptor: a computational study

“…We have also employed MP2 level along with DFT method MPW1PW91/6-31G(d) to examine the binding preferences in aqueous medium of Cp-M complexes. MP2/6-31+G(d) level of theory has been employed to investigate the binding affinity of alkali metal ions with benzene and inorganic benzene [75]. The interaction of benzene with Na + and K + ions calculated with MP2/6-31+G(d) level of theory is similar to that reported in the earlier report (Table S2).…”

A stress tensor and QTAIM perspective on the substituent effects of biphenyl subjected to torsion

“…This includes, in particular, the work of Popelier who used a similarity measure in the form of a BCP (bond critical point) space to accurately predicted the Hammett σ p and σ m values for benzoic acids . Other more recent work has also provided QTAIM perspectives on Hammett constants …”