Cooperativity of π-stacking and hydrogen bonding interactions and substituent effects on X-ben‖pyr⋯H–F complexes

Abstract

Quantum chemical calculations have been performed to gauge the effect of pi-stacking and hydrogen bonding interactions on each other in X-ben//pyr...H-F (X = NO(2), CF(3), CN, F, Cl, CH(3) and OH) complexes. The results indicate the cooperativity of interactions in these complexes where face-to-face aromatic interactions and hydrogen bonding interactions coexist. The effects of substituents on the X-ben//pyr...H-F complexes have also been studied with the MP2 method using 6-31G** basis set. The total binding energy increases in both electron-donating and withdrawing substituents. Herein, computational results indicate an enhanced pi-stacking interaction for all substituted complexes related to an unsubstituted case. On the other hand, H...N hydrogen bond interaction is declined by strong electron withdrawing substituents (NO(2) and CN) only. The cooperativity of pi-stacking and H...N hydrogen bond interaction has also been studied by using the atoms in molecules (AIM), natural bond orbital (NBO) and molecular electrostatic potential (MEP) analyses. There are good relationships between the Hammett constants and energy data, geometrical parameters, and the results of population analysis in X-ben//pyr...H-F and X-ben//pyr complexes. The characteristics of interactions are directly related to the electrostatic interaction between the rings.

Substituent Effects on Non‐Covalent Interactions with Aromatic Rings: Insights from Computational Chemistry

“…As previously observed in the benzene dimer, Ebrahimi and coworkers [41] showed, among other things, that both electron-withdrawing and electron-accepting substituents enhance the benzene-pyridine stacking interaction.…”

“…Ebrahimi et al [41] examined benzene-pyridine stacking interactions in the presence of an HÀF molecule hydrogen-bonded to the pyridine nitrogen. As previously observed in the benzene dimer, Ebrahimi and coworkers [41] showed, among other things, that both electron-withdrawing and electron-accepting substituents enhance the benzene-pyridine stacking interaction.…”

Simultaneous interactions of pyridine with substituted benzene ring and H–F in X-ben⊥pyr···H–F complexes: a cooperative study

“…In the previous work [19], we have concluded that, regardless of the nature of electron-withdrawing or donating substituents, the binding energies of X-ben||pyrÁÁÁH-F complexes increase compared to X-ben||pyrÁÁÁH-F (X = H) complex. In the present work, we investigated the same conclusion made on the case of X-ben\pyrÁÁÁH-F complexes; but in X-ben\pyrÁÁÁH-F complexes only electron-donating substituents increase the binding energies compared to X-ben\pyrÁÁÁH-F (X = H) complex.…”

“…Surprisingly, relatively little work has been done to systematically explore the fundamental question of how hydrogen bonding influences stacking interactions and vice versa [19,[24][25][26].…”

“…In our previous works, we studied the effects of substituents on X-pyridineÁÁÁH-F hydrogen bond [46], and the cooperative effects between p-p stacking and hydrogen bond interactions and substituent effects in X-ben||pyrÁÁÁH-F complexes are investigated as well [19].…”