SMARTER crystallography of the fluorinated inorganic–organic compound Zn3Al2F12·[HAmTAZ]6

Abstract

We present in this paper the structure resolution of a fluorinated inorganic–organic compound—Zn₃Al₂F₁₂·[HAmTAZ]₆—by SMARTER crystallography, i.e. by combining powder X-ray diffraction crystallography, NMR crystallography and chemical modelling of crystal (structure optimization and NMR parameter calculations). Such an approach is of particular interest for this class of fluorinated inorganic–organic compound materials since all the atoms have NMR accessible isotopes (¹H, ¹³C, ¹⁵N, ¹⁹F, ²⁷Al, ⁶⁷Zn). In Zn₃Al₂F₁₂·[HAmTAZ]₆, ²⁷Al and high-field ¹⁹F and ⁶⁷Zn NMR give access to the inorganic framework while ¹H, ¹³C and ¹⁵N NMR yield insights into the organic linkers. From these NMR experiments, parts of the integrant unit are determined and used as input data for the search of a structural model from the powder diffraction data. The optimization of the atomic positions and the calculations of NMR parameters (²⁷Al and ⁶⁷Zn quadrupolar parameters and ¹⁹F, ¹H, ¹³C and ¹⁵N isotropic chemical shifts) are then performed using a density functional theory (DFT) based code. The good agreement between experimental and DFT-calculated NMR parameters validates the proposed optimized structure. The example of Zn₃Al₂F₁₂·[HAmTAZ]₆ shows that structural models can be obtained in fluorinated hybrids by SMARTER crystallography on a polycrystalline powder with an accuracy similar to those obtained from single-crystal X-ray diffraction data.