Density-functional computation of 53Cr NMR chemical shifts

99Tc chemical shifts of TcO4−, TcH92−, TcOF5, TcO2F4−, TcOCl4−, Tc2(CO)10, and Tc(CO)3L3+ (L = CO, MeCN, H2O) 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(99Tc) 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 99Tc NMR line widths. Thermal and solvation effects on magnetic shielding constants of aqueous TcO4−, as assessed by averaging these properties over trajectories from Car–Parrinello molecular dynamics simulations, are indicated to be small and comparable to those of MnO4−. Complexation to aqueous uranyl, UO22+, is predicted to affect δ(99Tc) of TcO4− only slightly; somewhat larger complexation shifts are obtained for the oxygen nuclei of pertechnetate, suggesting that 17O NMR could be a useful probe for the extent of association between both radionuclides in solution. Copyright © 2008 John Wiley & Sons, Ltd.