From clusters to liquid: what are the preferred ways for benzene and pyrrole to interact?

Abstract

The various interactions occurring between pyrrole and benzene are a particularly appropriate model, as they are viewed as better X–H···π examples. A combined and sequential use of Quantum Mechanical (QM) calculations and Molecular Dynamics (MD) simulations was applied to investigate the different intermolecular interactions for benzene and pyrrole as clusters and its liquid mixture. All the cluster structures were fully optimized by the B2PLYP-D methods (including dispersion correction) with jun-cc-pVTZ (a revised aug-cc-pVTZ basis set). MD simulation with OPLS-AA force field was used to study the liquid mixture of benzene/pyrrole at different temperatures. Two types of N–H···π hydrogen bonds are preferred interactions compared with C–H···π interactions, either as clusters or as its liquid mixture. Based on the QM results, we clarify the difference in red-shifts of N–H bond of N–H···π hydrogen bonds observed by Jet FT-IR (Phys Chem Chem Phys 10: 2827, 2008). Meanwhile, the nature of various X–H···π interactions is unveiled by atoms in molecules (AIM), natural bond orbital and energy decomposition analysis (EDA). Furthermore, in light of QM results, MD simulation results further characterize the behavior and structural properties of these interactions. Finally, we proposed an original idea to explain the strength variation of different N–H···π hydrogen bond in liquid mixture based on AIM and EDA analysis.