2 research outputs found
NMR Crystallography for Structural Characterization of Oxovanadium(V) Complexes: Deriving Coordination Geometry and Detecting Weakly Coordinated Ligands at Atomic Resolution in the Solid State
No full textNMR
crystallography is an emerging method for atomic-resolution
structural analysis of ubiquitous vanadium(V) sites in inorganic and
bioinorganic complexes as well as vanadium-containing proteins. NMR
crystallography allows for characterization of vanadium(V) containing
solids, based on the simultaneous measurement of <sup>51</sup>V–<sup>15</sup>N internuclear distances and anisotropic spin interactions,
described by <sup>13</sup>C, <sup>15</sup>N, and <sup>51</sup>V chemical
shift anisotropy and <sup>51</sup>V electric field gradient tensors.
We show that the experimental <sup>51</sup>V, <sup>13</sup>C, and <sup>15</sup>N NMR parameters are essential for inferring correct coordination
numbers and deriving correct geometries in density functional theory
(DFT) calculations, particularly in the absence of single-crystal
X-ray structures. We first validate this approach on a structurally
known vanadium(V) complex, (<sup>15</sup>N-salicylideneglycinate)-(benzhydroxamate)oxovanadium(V),
VO<sup>15</sup>NGlySalbz. We then apply this approach to derive the
three-dimensional structure of (methoxo)(<sup>15</sup>N-salicylidene-glycinato)oxovanadium(V)
with solvated methanol, [VO(<sup>15</sup>NGlySal)(OCH<sub>3</sub>)]·(CH<sub>3</sub>OH). This is a representative complex
with potentially variable coordination geometry depending on the solvation
level of the solid. The solid material containing molecules of CH<sub>3</sub>OH, formally expressed as [VO(<sup>15</sup>NGlySal)(OCH<sub>3</sub>)]·(CH<sub>3</sub>OH), is found to have one molecule
of CH<sub>3</sub>OH weakly coordinated to the vanadium. The material
is therefore best described as [VO(<sup>15</sup>NGlySal)(OCH<sub>3</sub>)(CH<sub>3</sub>OH)] as deduced by the combination of
multinuclear solid-state NMR experiments and DFT calculations. The
approach reported here can be used for structural analysis of systems
that are not amenable to single-crystal X-ray diffraction characterization
and which can contain weakly associated solvents
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