Electron density and elastic properties of crystalline [Co(NH₃)₅NO₂]ClNO₃: a quantum crystallography study.

Intermolecular interactions in crystalline [Co(NH3)5NO2]ClNO3 are related to macroscopic elastic properties and photomechanical effects accompanying solid‐state linkage isomerization in this compound. The electron‐density features between anions and the complex cation are shown to prevent direct interaction of these fragments. The superposition of electrostatic potential and electron‐density gradient fields suggests the indirect mechanism of anion interactions with each other through ligands. The non‐covalent intermolecular contacts and hydrogen bonds are shown to occupy the 'soft' intermolecular space forming the negative channels of quantum electronic pressure and thus can rearrange easily on anion substitution. The work rationalizes previous experimental studies of the mechanical properties of [Co(NH3)5NO2]ClNO3. The elastic properties modelled based on the structural information are in agreement with the experimental structural data. The correlation between the total and quantum pressure of separate non‐covalent contacts and their quantitative analogues derived from the macroscopic elastic tensor is discussed. Conclusions on the anisotropy of mechanical properties and its link with bond continuum features are drawn. [ABSTRACT FROM AUTHOR]