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--Zn(3)Al(2)F(12)·[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 ((1)H, (13)C, (15)N, (19)F, (27)Al, (67)Zn). In Zn(3)Al(2)F(12)·[HAmTAZ](6), (27)Al and high-field (19)F and (67)Zn NMR give access to the inorganic framework while (1)H, (13)C and (15)N 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 ((27)Al and (67)Zn quadrupolar parameters and (19)F, (1)H, (13)C and (15)N 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 Zn(3)Al(2)F(12)·[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.

Exploiting the Synergy of Powder X-ray Diffraction and Solid-State NMR Spectroscopy in Structure Determination of Organic Molecular Solids

“…Examples include a number of strategies for the structure determination of inorganic framework structures 57,58 and hybrid organic–inorganic materials, 59 as well as for elucidating specific structural details (in particular, hydrogen-bonding arrangements) for materials of mineralogical interest. 60,61 In addition, DFT-based chemical shift calculations have been employed successfully to augment the process of structure determination of an organic polymer from wide-angle X-ray and wide-angle neutron diffraction techniques.…”

Combining solid-state NMR spectroscopy with first-principles calculations – a guide to NMR crystallography

“…In recent years, the advances in NMR spectroscopy, and its growing use for determining or refining structural models, have led to the emergence of a new field, termed ''NMR Crystallography''. 10,11 While more generally defined in terms of the use of NMR spectroscopy (often in combination with diffraction experiments) to determine structural information, in many applications calculation also plays a major role (an approach sometimes referred to as ''SMARTER Crystallography'' 12 ). In all cases, however, the ultimate goal is for the combination of a number of methods to be able to provide much greater insight than any individual approach.…”

Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs)

“…Electron paramagnetic resonance spectroscopy (EPR [31]) and various NMR spectroscopic techniques including diffusion measurements using pulsed field gradient (PFG) NMR [32] as well as 129 Xe NMR spectroscopy are very useful in combination with XRD. Therefore, increased efforts are made in order to combine powder X-ray diffraction, NMR crystallography [33,34], and molecular modeling [35]; an approach which is referred to as structure elucidation by combining magnetic resonance, computational modeling and diffraction (SMARTER, see, e.g., [36]). Thereby, the chemical shifts can be computed ab initio using pseudopotenials as implemented in the gauge-including projector augmented-wave (GIPAW [35]) approach.…”