Density functional computation of 55Mn NMR parameters
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Gradient-corrected (GGA) and hybrid variants of density functional theory are used to compute geometries and 55Mn chemical shifts of MnO4−, Mn(CO)6+, Mn2(CO)10, Mn(CO)5X [X=H, Cl, C(O)Me], Mn(CO)5−, Mn(NO)3(CO), and Mn(C5H5)L x [L x =(CO)3, C6H6, C7H8]. For this set of compounds, substituent effects on δ(55Mn) are significantly underestimated with the pure GGA functional BPW91 and are well described with hybrid functionals such as mPW1PW91 and, in particular, B3LYP. The computed data provide evidence for solvent and counterion effects on δ(55Mn) of MnO4− and Mn(CO)6+, respectively. The latter, in the presence of Cl−, may be described as highly fluxional Mn(CO)5C(O)Cl. Electric field gradients computed with the B3LYP functional can be used for a qualitative rationalization of observed trends in 55Mn NMR line widths. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s002140020338x
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