(Received: May 18, 2004; Accepted for publication: July 9, 2004; Published on Web: November 26, 2004)
A series of calculations of halogen nuclear magnetic shielding constants and chemical shifts in X- and XO4- (X = F, Cl, Br, I) were carried out to discuss the relativistic and electron-correlation effects and, especially, the non-additivity of both effects. The second-order Douglas-Kroll-Hess method was used as a relativistic method, and the Moller-Plesset method was applied to the generalized UHF wave function. The calculated chemical shifts in ClO4- and IO4- agree reasonably well with the observed ones, though there are no experimental values in FO4- and BrO4-. The relativistic effect was quite large especially in IO4- as reported previously, while the electron-correlation effect is significant in both FO4- and IO4-. The non-additivity of the relativistic and the electron-correlation effects in magnetic shielding constants is unexpectedly large in IO4-, and therefore a relativistic electron-correlated method is crucial for describing accurate heavy-element nuclear magnetic shielding constants and chemical shifts.
Keywords: Nuclear magnetic shielding,, Chemical shift, NMR, Relativistic effect, Electron-correlation effect
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