Insight into Magnesium Coordination Environments in Benzoate and Salicylate Complexes through 25Mg Solid-State NMR Spectroscopy

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• 作者：Kevin M. N. Burgess ; Yang Xu ; Matthew C. Leclerc ; David L. Bryce
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：August 1, 2013
• 年：2013
• 卷：117
• 期：30
• 页码：6561-6570
• 全文大小：431K
• 年卷期：v.117,no.30(August 1, 2013)
• ISSN：1520-5215

文摘

We report on the ²⁵Mg solid-state nuclear magnetic resonance (NMR) characterization of a series of magnesium complexes featuring Mg²⁺ ions in organic coordination environments. Six compounds have been synthesized with benzoate and salicylate ligands, which are typically used as linkers in metal organic frameworks (MOFs). The use of ultrahigh-field solid-state NMR has revealed a relatively large range of values for the ²⁵Mg quadrupolar coupling constant, C_Q(²⁵Mg), in these compounds. In contrast to some previously studied inorganic Mg²⁺ complexes, the values of C_Q(²⁵Mg) in organic Mg²⁺ complexes are well rationalized by the degree of octahedral strain of the 鈥淢gO₆鈥?coordination polyhedra. ¹³C and ²⁵Mg isotropic chemical shifts were also found to be sensitive to the binding mode of the carboxylate ligands. The experimental findings are corroborated by gauge-including projector-augmented-wave (GIPAW) density functional theory (DFT) computations, and these have allowed for an interpretation of the experimentally observed trend in the C_Q(²⁵Mg) values and for the visualization of the EFG tensor principal components with respect to the molecular structure. These new insights may prove to be valuable for the understanding and interpretation of ²⁵Mg NMR data for Mg²⁺ ions in organic binding environments such as those found in MOFs and protein-divalent metal binding sites.