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Density‐functional computation of 99 Tc NMR chemical shifts
Author(s) -
Bühl Michael,
Golubnychiy Volodymyr
Publication year - 2008
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2276
Subject(s) - chemistry , chemical shift , aqueous solution , electric field gradient , atomic orbital , uranyl , density functional theory , solvation , computational chemistry , molecule , quadrupole , atomic physics , organic chemistry , ion , physics , quantum mechanics , electron
99 Tc chemical shifts of TcO 4 − , TcH 9 2− , TcOF 5 , TcO 2 F 4 − , TcOCl 4 − , Tc 2 (CO) 10 , and Tc(CO) 3 L 3 + (L = CO, MeCN, H 2 O) are computed using geometries optimized with the gradient‐corrected BP86 and hybrid B3P86 density functionals, at the gauge‐including atomic orbitals (GIAO), ‐BPW91 and ‐B3LYP levels. For this set of compounds, substituent effects on δ( 99 Tc) are better described with the pure BPW91 functional than with B3LYP, in contrast to most other transition‐metal chemical shifts studied so far. A rough, qualitative correlation is found between computed electric‐field gradients at the Tc nuclei and the corresponding 99 Tc NMR line widths. Thermal and solvation effects on magnetic shielding constants of aqueous TcO 4 − , as assessed by averaging these properties over trajectories from Car–Parrinello molecular dynamics simulations, are indicated to be small and comparable to those of MnO 4 − . Complexation to aqueous uranyl, UO 2 2+ , is predicted to affect δ( 99 Tc) of TcO 4 − only slightly; somewhat larger complexation shifts are obtained for the oxygen nuclei of pertechnetate, suggesting that 17 O NMR could be a useful probe for the extent of association between both radionuclides in solution. Copyright © 2008 John Wiley & Sons, Ltd.