Ramanathan N, Sankaran K, Sundararajan K
Materials Chemistry & Metal Fuel Cycle Group, ‡Homi Bhabha National Institute, Indira Gandhi Center for Atomic Research , Kalpakkam 603102, Tamil Nadu, India.
J Phys Chem A. 2017 Nov 30;121(47):9081-9091. doi: 10.1021/acs.jpca.7b08164. Epub 2017 Nov 15.
Spectroscopy under isolated conditions at low temperatures is an excellent tool to characterize the aggregates stabilized through weak interactions. Within the framework of weak interactions, the π-stacking interactions are considered unconventional with the limited experimental proofs, wherein the bonding associates are either aromatic and heterocyclic compounds or their combinations. Besides aromatic compounds, π-stacking networks can even be realized with molecules possessing electron rich π-clouds. In this work, the N molecule as a possible π-bonding partner is explored for the first time in which hetero π-stacking was achieved between pyrrole and N precursors. The matrix isolation experiments performed by seeding pyrrole and N mixtures in an Ar matrix at low temperatures with subsequent infrared spectral characterization revealed the generation of adducts stabilized through a π(pyrrole)···π(N) interaction. Under identical conditions with the likelihood of two competing π-stacking and hydrogen-bonding interactions in pyrrole-N associates, π-stacking dominates energetically over hydrogen-bonding interaction.
低温下的孤立条件光谱学是表征通过弱相互作用稳定的聚集体的出色工具。在弱相互作用的框架内，π-堆积相互作用被认为是非传统的，实验证据有限，其中键合缔合体要么是芳香族和杂环化合物，要么是它们的组合。除了芳香族化合物，π-堆积网络甚至可以由具有富电子π-云的分子实现。在这项工作中，首次探索了N分子作为可能的π键合伙伴，其中在吡咯和N前体之间实现了杂π-堆积。通过在低温下将吡咯和N混合物播种到Ar基质中并随后进行红外光谱表征进行的基质隔离实验揭示了通过π(吡咯)···π(N)相互作用稳定的加合物的生成。在相同条件下，吡咯-N缔合体中存在两种相互竞争的π-堆积和氢键相互作用的可能性，在能量上π-堆积比氢键相互作用占主导。
