Cation−π Interactions: Accurate Intermolecular Potential from Symmetry-Adapted Perturbation Theory

Abstract

Symmetry-adapted perturbation theory (SAPT) is used to decompose the total intermolecular interaction energy between the ammonium cation and a benzene molecule into four physically motivated individual contributions: electrostatics, exchange, dispersion, and induction. Based on this rigorous decomposition, it is shown unambiguously that both the electrostatic and the induction energy components contribute almost equally to the attractive forces stabilizing the dimer with a nonnegligible contribution coming from the dispersion term. A polarizable potential model for the interaction of ammonium cation with benzene is parametrized by fitting these four energy components separately using the functional forms of the AMOEBA force field augmented with the missing charge penetration energy term calculated as a sum over pairwise electrostatic energies between spherical atoms. It is shown that the proposed model is able to produce accurate intermolecular interaction energies as compared to ab initio results, thus avoiding error compensation to a large extent.

Improving the Force Field Description of Tyrosine–Choline Cation−π Interactions: QM Investigation of Phenol–N(Me)4+ Interactions

“…15, 16, 52, 56 In the present study we show that all approach angles need to be considered. This leads to overall improvement in the reproduction of the QM data along different approach directions, though the quality of the agreement does depend on the different directions (Cf.…”

The dimer-approach to characterize opto-electronic properties of and exciton trapping and diffusion in organic semiconductor aggregates and crystals

“…To simulate the a-PTCDA environment, we employ the AMOEBA polarizable force field 103 while a new force field had to be developed for DIP. [104][105][106] For the computation of the inner dimer we used the SCS-CC2 approach, 107 because multi-reference configuration interaction calculations 108,109 are way too expensive for the given systems.…”

QM/MM calculations combined with the dimer approach on the static disorder at organic‐organic interfaces of thin‐film organic solar cells composed of small molecules

“…[61] This is again confirmed by comparing the solvent shifts of the ground state and the ionized state of all molecules modeled by state-specific solvation models (see Supporting Information). The response of the ionized state to changes in the environment differs significantly from that of the neutral ground state.…”

“…[58,59] It was sufficiently accurate so that special parametrizations were not necessary. [60,61] Final states energies E QM/MM were calculated from the dimer energies obtained in the QM calculation E QM (dimer) (which includes the electrostatic interaction energy with the environment) and the difference of the force field energies of the total system and the QM system E MM (total) − E MM (dimer), the latter corrected for the electrostatic force field interaction energy calculated as the difference E MM , el (total) − E MM , el (dimer).…”

“…[58,59] It was sufficiently accurate so that special parametrizations were not necessary. [60,61] Final states energies E QM/MM were calculated from the dimer energies obtained in the QM calculation E QM (dimer) (which includes the electrostatic interaction energy with the environment) and the difference of the force field energies of the total system and the QM system E MM (total) − E MM (dimer), the latter corrected for the electrostatic force field interaction energy calculated as the difference E MM , el (total) − E MM , el (dimer).Andrienko et al demonstrated the importance of the longrange character of electrostatic interactions and the very slow convergence of charge-charge and charge-quadrupole interactions. [62] To verify that the constructed supercells are sufficiently large to obtain converged values for the interaction energies of the QM system with the environment (and to keep our calculations computationally feasible for AMOEBA), we divided the supercell into layers (innermost interface area, 2 outer monomer layers, 2 outer fullerene layers, Figure 2C).…”