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

ABSTRACT: 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, CQ( 25Mg), in these compounds. In contrast to some previously studied inorganic Mg2+ complexes, the values of CQ( 25Mg) in organic Mg2+ complexes are well rationalized by the degree of octahedral strain of the “MgO6” 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 hav