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51V Solid-State Magic Angle Spinning NMR Spectroscopy and DFT Studies of Oxovanadium(V) Complexes Mimicking the Active Site of Vanadium Haloperoxidases

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posted on 25.01.2003, 00:00 by Neela Pooransingh, Ekaterina Pomerantseva, Martin Ebel, Sven Jantzen, Dieter Rehder, Tatyana Polenova
A series of 11 oxovanadium(V) complexes mimicking the active site of vanadium haloperoxidases have been investigated by 51V magic angle spinning NMR spectroscopy and density functional theory (DFT). The MAS spectra are dominated by the anisotropic quadrupolar and chemical shielding interactions; for these compounds, CQ ranges from 3 to 8 MHz, and δσ is in the range 340−730 ppm. The quadrupolar coupling and chemical shielding tensors as well as their relative orientations have been determined by numerical simulations of the spectra. The spectroscopic NMR observables appear to be very sensitive to the details of the electronic and geometric environment of the vanadium center in these complexes. For the four crystallographically characterized compounds from the series, the quadrupolar and chemical shielding anisotropies were computed at the DFT level using two different basis sets, and the calculated tensors were in general agreement with the experimental solid-state NMR data. A combination of 51V solid-state NMR and computational methods is thus beneficial for investigation of the electrostatic and geometric environment in diamagnetic vanadium systems with moderate quadrupolar anisotropies.

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