Simulation of 59Co NMR Chemical Shifts in Aqueous Solution

59Co chemical shifts were computed at the GIAO-B3LYP level for [Co(CN)6]3−, [Co(H2O)6]3+, [Co(NH3)6]3+, and [Co(CO)4]− in water. The aqueous solutions were modeled by Car–Parrinello molecular dynamics (CPMD) simulations, or by propagation on a hybrid quantum-mechanical/molecular-mechanical Born–Oppenheimer surface (QM/MM-BOMD). Mean absolute deviations from experiment obtained with these methods are on the order of 400 and 600 ppm, respectively, over a total δ(59Co) range of about 18 000 ppm. The effect of the solvent on δ(59Co) is mostly indirect, resulting primarily from substantial metal–ligand bond contractions on going from the gas phase to the bulk. The simulated solvent effects on geometries and δ(59Co) values are well reproduced by using a polarizable continuum model (PCM), based on optimization and perturbational evaluation of quantum-mechanical zero-point corrections.