Pressure‐Induced Encapsulation of Cs⁺ Cations within an 18‐Crown‐6 Cavity: Insights from X‐ray Diffraction, Raman Spectroscopy, and DFT Calculations

Abstract

This study utilizes single‐crystal X‐ray diffraction in a diamond anvil cell (DAC) to explore the structural response of [Cs(18‐Crown‐6)][SbCl6] under high pressure (HP). Notably, the pressure drives large Cs atoms closer to the center of the crown ether cavity, ultimately requiring pressures of 3 GPa for its complete encapsulation. Remarkably, the absence of short contacts in the crystal classifies the material as a "loose crystal" offering a unique model for understanding compression mechanisms. The crystal exhibits highly anisotropic compression behavior with an impressive volume reduction and non‐linear pressure – unit‐cell parameters relationships facilitated by the absence of short CH···Cl contacts up to 0.9 GPa. Beyond this pressure, steric repulsion due to shortening H···Cl and H···H interactions hinders further effective compression, so pressure dependence on unit cell parameters and volume becomes more linear. The behavior of [Cs(18‐Crown‐6)][SbCl6] at different conditions was studied using Raman spectroscopy and supplemented by DFT calculations.