NMR Research Group, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014, Finland.
Phys Chem Chem Phys. 2011 Dec 21;13(47):21016-25. doi: 10.1039/c1cp22043h. Epub 2011 Oct 20.
The leading-order perturbation theory approach to relativistic effects on the nuclear magnetic shielding provides an economic method for obtaining the chemical shifts in heavy-element containing systems. The method features detailed analysis potential in terms of the different physical mechanisms affecting the shielding tensors of heavy nuclei. The perturbative nature, however, results in an increasing error with increasingly heavy elements in the system. In this work, we investigate the performance of the Breit-Pauli perturbation theory (BPPT) against fully relativistic four-component theory in computing the nuclear shielding constants as well as the chemical shifts with respect to corresponding atomic ions of group-12 metals, M = Zn, Cd, and Hg, in dimethyl M(CH(3))(2) and aqueous M(H(2)O)(6)(2+) complexes. It is shown that five out of the total of sixteen BPPT correction terms are responsible for most of the relativistic corrections for the chemical shift of studied metals. The relativity is important already for Cd and BPPT is proven to work well up to Hg for the chemical shift, as calibrated with the fully relativistic method.
相对论效应对核磁共振屏蔽的一级微扰理论方法为研究含重元素体系的化学位移提供了一种经济的方法。该方法的特点是能够详细分析影响重核屏蔽张量的不同物理机制。然而，由于微扰性质，随着体系中元素的逐渐加重，误差也会不断增加。在这项工作中，我们研究了 Breit-Pauli 微扰理论（BPPT）与完全相对论四分量理论在计算 12 族金属 M（M = Zn、Cd 和 Hg）的二甲基 M（CH（3））（2）和水合 M（H（2）O）（6）（2+）络合物的核磁共振屏蔽常数以及相对于相应原子离子的化学位移方面的性能。结果表明，在十六个 BPPT 校正项中，总共有五个校正项对所研究金属的化学位移的相对论修正起主要作用。对于 Cd，相对论是很重要的，而 BPPT 在经过与完全相对论方法的校准后，被证明在化学位移方面对 Hg 也有效。
