A Concerted Approach for the Determination of Molecular Conformation in Ordered and Disordered Materials

Abstract

We present the successful application of a concerted approach for the investigation of the local environment in ordered and disordered phases in the solid state. In this approach we combined isotope labeling with computational methods and different solid-state NMR techniques. We chose triphenylphosphite (TPP) as an interesting example of our investigations because TPP exhibits two crystalline modifications and two different amorphous phases one of which is highly correlated. In particular we analyzed the conformational distribution in three of these phases. A sample of triply labeled 1-[13C]TPP was prepared and 1D MAS as well as wide-line 13C NMR spectra were measured. Furthermore we acquired 2D 13C wide-line exchange spectra and used this method to derive highly detailed information about the phenyl orientation in the investigated TPP phases. For linkage with a structure model a DFT analysis of the TPP molecule and its immediate environment was carried out. The ab initio calculations of the 13C chemical shift tensor in three- and six-spin systems served as a base for the calculation of 1D and 2D spectra. By comparing these simulations to the experiment an explicit picture of all phases could be drawn on a molecular level. Our results therefore reveal the high potential of the presented approach for detailed studies of the mesoscopic environment even in the challenging case of amorphous materials.

Ab Initio Calculation of Solid-State NMR Spectra for Different Triazine and Heptazine Based Structure Proposals of g-C3N4

“…The full NMR chemical shift tensor was reduced and transformed into its principal axis system, as described in the literature. 45 The principle values were sorted according to σ 11 e σ 22 e σ 33 and the anisotropy analyzed in terms of the span, Ω, and skew, κ, of the tensor, as can be found in the literature as well. 46 Using the reported definitions, these values can easily be transformed into the classical descriptions of the NMR tensor, either via the anisotropy, ∆, or the reduced anisotropy, δ, and the asymmetry, η.…”

“…The planar and corrugated PM3 models shown in Figure , II(a), and Figure were further used for the computation of the NMR chemical shift tensor on the PBE1PBE/6-31G(d) and PBE1PBE/6-31G(d,p) level of theory, respectively. The full NMR chemical shift tensor was reduced and transformed into its principal axis system, as described in the literature . The principle values were sorted according to σ 11 ≤ σ 22 ≤ σ 33 and the anisotropy analyzed in terms of the span, Ω, and skew, κ, of the tensor, as can be found in the literature as well .…”

Synthesis and Solid-State Study of Supramolecular Host−Guest Assemblies: Bis[6-O,6-O′-(1,2:3,4-diisopropylidene-α-d-galactopyranosyl)thiophosphoryl] Dichalcogenides

“…This subject was recently exhaustively reviewed by Ravy et al 18 Sehnet and Senker have reported a concerted approach for determination of the local environment in ordered and disordered phases in the solid state. 19 The case of TCSC seems to be very special. XRD and SSNMR spectroscopy do not answer the question regarding the organization of components 1, 2, and 3 in the unit cell.…”

Identifying Selective Host–Guest Interactions Based on Hydrogen Bond Donor–Acceptor Pattern in Functionalized Al-MIL-53 Metal–Organic Frameworks

“…To obtain information about the location and alignment of guest molecules within the framework, homo- and heteronuclear connectivities and distances as well as the orientation correlation of neighboring chemical shift tensors have to be obtained. For this purpose, a variety of one- and two-dimensional (2D) NMR experiments might be used, ranging from cross-polarization schemes with and without homonuclear decoupling on the I spin system − over high-resolution double-quantum − and zero-quantum − experiments up to wide-line radio frequency driven spin-diffusion techniques. , In any case, a prerequisite for such studies is an unequivocal assignment of individual resonances to characteristic building units. For MOFs, this is usually straightforward for heteronuclei with a large chemical shift range like 13 C and 15 N. Typically, such nuclei possess a low natural abundance combined with a small gyromagnetic ratio γ.…”