Directed anisotropy in bis(acetato-k2O,O')diaquazinc(II) at 110 and 250 K

The molecule of the title compound, [Zn(C2H3O2)2(H2O)2], is located on a twofold axis in the crystal structure. The displacement parameters and the thermal expansion of the crystal show significant anisotropy. This is explained by the two-dimensional hydrogen-bonded structure, with only very weak interactions perpendicular to it. Besides the overall molecular motion, there are internal vibrations, which cause the Zn—O(carboxylate) bonds to fail the Hirshfeld rigid-bond test. It is shown that this can be interpreted in terms of the steric strain in the four-membered chelate ring due to the bidentate carboxylate coordination.