Characterization of metal centers in bioinorganic complexes using ab initio calculations of 113Cd chemical shifts

Determination of Cd-113 chemical shift is of significant interest in NMR characterization of metal porphyrins, metal-histidine interactions, and other metal-ligand interactions in many bioinorganic complexes and metalloproteins. In this study, we present a detailed account of a number of quantum chemical investigations aimed at relating isotropic and anisotropic Cd-113 chemical shifts to the structure of several biologically relevant complexes with discrete and polymeric structures. Calculated and experimentally determined chemical shift values are compared to correlate the variation of the chemical shift values with the structural changes around the metal center. Our results infer that the density functional theory using the Sadlej basis set on the cadmium atom is a suitable method for estimating cadmium shielding values to a reasonable accuracy.