Unravelling the effect of paramagnetic Ni2+ on the 13C NMR shift tensor for carbonate in Mg2−xNixAl layered double hydroxides by quantum-chemical computations
|Author:||Mohan, Megha1; Andersen, Anders B. A.2; Mareš, Jiří1;|
1NMR Research Unit, P.O. Box 3000, FI-90014 University of Oulu, Finland
2Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark
|Online Access:||PDF Full Text (PDF, 3.6 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe20231101142167
Royal Society of Chemistry,
|Publish Date:|| 2023-11-01
Structural disorder and low crystallinity render it challenging to characterise the atomic-level structure of layered double hydroxides (LDH). We report a novel multi-step, first-principles computational workflow for the analysis of paramagnetic solid-state NMR of complex inorganic systems such as LDH, which are commonly used as catalysts and energy storage materials. A series of ₁₃CO₃²⁻-labelled Mg2−xNixAl-LDH, x ranging from 0 (Mg₂Al-LDH) to 2 (Ni₂Al-LDH), features three distinct eigenvalues δ₁₁, δ₂₂ and δ₃₃ of the experimental ₁₃C chemical shift tensor. The δii correlate directly with the concentration of the paramagnetic Ni²⁺ and span a range of |δ₁₁ − δ₃₃| ≈ 90 ppm at x = 0, increasing to 950 ppm at x = 2. In contrast, the isotropic shift, δiso(¹³C), only varies by −14 ppm in the series. Detailed insight is obtained by computing (1) the orbital shielding by periodic density-functional theory involving interlayer water, (2) the long-range pseudocontact contribution of the randomly distributed Ni²⁺ ions in the cation layers (characterised by an ab initio susceptibility tensor) by a lattice sum, and (3) the close-range hyperfine terms using a full first-principles shielding machinery. A pseudohydrogen-terminated two-layer cluster model is used to compute (3), particularly the contact terms. Due to negative spin density contribution at the ¹³C site arising from the close-by Ni²⁺ sites, this step is necessary to reach a semiquantitative agreement with experiment. These findings influence future NMR investigations of the formally closed-shell interlayer species within LDH, such as the anions or water. Furthermore, the workflow is applicable to a variety of complex materials.
PCCP. Physical chemistry chemical physics
|Pages:||24081 - 24096|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
116 Chemical sciences
We acknowledge funding from the Academy of Finland (grant 331008) and University of Oulu (Kvantum Institute, MM, JM, JV), European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska–Curie (grant agreement no. 713606, MM), the Danish Council for Independent Research Science and Universe (grant DFF-7014-00198; UGN, ABAA, JV).
|EU Grant Number:||
(713606) I4FUTURE - Novel Imaging and Characterisation Methods in Bio, Medical, and Environmental Research and Technology Innovations
|Academy of Finland Grant Number:||
331008 (Academy of Finland Funding decision)
This journal is © the Owner Societies 2023. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.