The effect of pressure on a nickel aspartate framework

The hydrostatic compression of the chiral metal-organic framework [Ni(L-Asp)(H2O)(2)] center dot H2O (NiAsp-I) has been studied to 6.07 GPa by single crystal X-ray diffraction. Over the course of this pressure range the compound undergoes a phase transition between 0.58 GPa and 1.26 GPa, yielding NiAsp-II. Both polymorphs are orthorhombic, P2(1)2(1)2(1), and feature 1D chains of Asp-Ni-Asp moieties. During the transition, the Ni(II) octahedra rotate, resulting in a dramatic shift in the position of the axial bonds with respect to the direction of polymer formation, and gives rise to an anisotropic compression of the unit cell dimensions.