Confinement inside a Crystalline Sponge Induces Pyrrole To Form N-H...π Bonded Tetramers

作者：Wu, Mengling; Zhang, Junle; Yuan, Liangqian; Rissanen, Kari^*; Pan, Fangfang^*

来源：Chemistry - A European Journal, 2021, 27(38): 9814-9819.

DOI：10.1002/chem.202100087

• aggregation
• confinement effects
• crystalline sponge method
• host-guest chemistry
• pyrrole tetramer

Based on the DFT-level-calculated molecular volume (V-mol) of pyrrole and its liquid density, pyrrole manifests the highest liquid density coefficient LDc (defined as [V(mol)xdensity x0.6023]/FW) value of 0.7. Normal liquids have LDc <0.63. This very high LDc is due to the strong N-H...pi interactions in solution, and hence pyrrole can be considered to be a pseudo-crystalline liquid. When trapped inside the confined space of a crystalline sponge, a reorientation of the N-H...pi interaction is observed leading to specific cyclic N-H...pi tetramers and N-H...pi dimers, as verified by single-crystal X-ray crystallographic and computational methods. These tetramers are of the same size as four pyrrole molecules in the solid-state of pyrrole, yet the cyclic N-H...pi intermolecular interactions are circularly oriented instead of being in the linear zigzag structure found in the X-ray structure of a solid pyrrole. The confinement thus acts as an external driving force for tetramer formation.

• 单位
  郑州大学