Sensitivity of Intra- and Intermolecular Interactions of Benzo[h]quinoline from Car-Parrinello Molecular Dynamics and Electronic Structure Inspection.

Jarosław J Panek,Aneta Jezierska,Joanna Zasada,Beata Kizior,Bartłomiej M Szyja

doi:10.3390/ijms22105220

Abstract

The O-H...N and O-H...O hydrogen bonds were investigated in 10-hydroxybenzo[h]quinoline (HBQ) and benzo[h]quinoline-2-methylresorcinol complex in vacuo, solvent and crystalline phases. The chosen systems contain analogous donor and acceptor moieties but differently coupled (intra- versus intermolecularly). Car–Parrinello molecular dynamics (CPMD) was employed to shed light onto principle components of interactions responsible for the self-assembly. It was applied to study the dynamics of the hydrogen bonds and vibrational features as well as to provide initial geometries for incorporation of quantum effects and electronic structure studies. The vibrational features were revealed using Fourier transformation of the autocorrelation function of atomic velocity and by inclusion of nuclear quantum effects on the O-H stretching solving vibrational Schrödinger equation a posteriori. The potential of mean force (Pmf) was computed for the whole trajectory to derive the probability density distribution and for the O-H stretching mode from the proton vibrational eigenfunctions and eigenvalues incorporating statistical sampling and nuclear quantum effects. The electronic structure changes of the benzo[h]quinoline-2-methylresorcinol dimer and trimers were studied based on Constrained Density Functional Theory (CDFT) whereas the Electron Localization Function (ELF) method was applied for all systems. It was found that the bridged proton is localized on the donor side in both investigated systems in vacuo. The crystalline phase simulations indicated bridged proton-sharing and transfer events in HBQ. These effects are even more pronounced when nuclear quantization is taken into account, and the quantized Pmf allows the proton to sample the acceptor area more efficiently. The CDFT indicated the charge depletion at the bridged proton for the analyzed dimer and trimers in solvent. The ELF analysis showed the presence of the isolated proton (a signature of the strongest hydrogen bonds) only in some parts of the HBQ crystal simulation. The collected data underline the importance of the intramolecular coupling between the donor and acceptor moieties.

Highlights

Qualitative and quantitative prediction of intra- and intermolecular forces responsible for the self-assembly of molecules has been widely investigated due to its importance in the design of new molecules with desired properties [1,2]
Car–Parrinello molecular dynamics (CPMD) simulations were performed for the HBQ molecule and dimer and trimers formed by benzo[h]quinoline-2methylresorcinol in vacuo
The electronic structure changes depending on the bridged proton position were examined based on Constrained Density Functional Theory (CDFT) and Electron Localization Function (ELF) methods

Summary

Introduction

Qualitative and quantitative prediction of intra- and intermolecular forces responsible for the self-assembly of molecules has been widely investigated due to its importance in the design of new molecules with desired properties [1,2]. Among the various noncovalent forces that need to be considered, one should name—in a rough series from the strongest to the weakest ones—the electrostatic attraction between charged moieties (which are not applicable to our current study), hydrogen bonds (HBs) providing a wide range of interaction energies, halogen, chalcogen, tetrel or pnicogen bonds—objects of recent intensive research [3,4,5], non-classical forms of hydrogen bonding (e.g., C-H...π contacts or charge-inverted HBs) [6,7], and omnipresent yet the weakest of all, dispersion forces Most of these forces are very sensitive to the modifications of the molecular skeleton, influence of the inductive and steric effects, or the changes in the environment (solvent or crystal fields). The applied procedure is equivalent to the combinatorial synthesis of crystals

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