Computational and experimental evidence of N–H…π and cooperative πN…π∗ interactions in pyrrole…benzene and pyrrole…ethylene heterodimers at low temperatures

• Published in: Journal of molecular structure 2020-06, Vol.1209, p.127983, Article 127983
• Main Authors: Sarkar, Shubhra, Ramanathan, N., Sruthi, P.K., Sundararajan, K.
• Format: Article
• Language: English
• Subjects: Benzene; Ethylene; Matrix isolation; N–H…π; Pyrrole; π…π
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2020.127983

The interaction between pyrrole with benzene and ethylene was investigated using matrix isolation infrared spectroscopy and ab initio computations. Computations indicated the global minimum structure of pyrrole-benzene and pyrrole-ethylene heterodimers are stabilized by π…σ∗ (N–H…π) and a cooperative πN…π∗ interactions. The present work for the first time, reports that pyrrole … benzene heterodimer is stabilized by both N–H…π and πN…π∗ interactions, where the latter induces a partial stacking in contrast to the T-shaped structure predicted by previous experimental and theoretical reports. To provide experimental proof, the heterodimers were trapped in N2 and Ar matrixes, and probed through infrared spectroscopy. Natural bond orbital (NBO) and energy decomposition (ED) analyses revealed that the heterodimers were stabilized by charge-transfer, electrostatic and dispersion interactions. To further understand and delineate the existence of πN…π∗ interaction (which results from partial π-stacking), computations were performed on the heterodimers of pyrrole with several acyclic and cyclic π-donors. •Interaction of C4H5N with C6H6 and C2H4 were studied at low temperatures.•Computations were performed at MP2/aug-cc-pVDZ level of theory.•NBO and EDA analysis were performed to understand the nature of the interaction.•Higher C4H5N–C6H6 and C4H5N–C2H4 clusters were also studied.