Relativistic prediction of Pt-195 NMR chemical shift using the NMR- DKH basis sets.

Abstract

Nuclear magnetic resonance (NMR) spectroscopy has played an important role in the discovery and design of new drugs with antitumor potential and the Pt-195 NMR has a fundamental role since the Pt-195 nucleus is very sensitive to the nature of the ligands in the coordination sphere and the oxidation state of the metal. The theoretical prediction of the Pt-195 NMR chemical shift is an extremely difficult task in which several factors must be taken into accounts, such as basis sets, electronic correlation, solvent, and relativistic effects. In an earlier study, Paschoal et al. developed the NMR-DKH basis sets and a nonrelativistic protocol for predicting the Pt-195 NMR chemical shift. The authors studied a set of 258 Pt(II) complexes and obtained a mean absolute deviation (MAD) of 168 ppm and a mean relative deviation (MRD) of 5%. However, relativistic calculations with the NMR-DKH basis sets have not been performed. Thus, the present work aims to apply the NMR-DKH in predicting the Pt-195 NMR chemical shift including the relativistic effects. The cisplatin was used as a model and its geometry was optimized and characterized as a minimum point on the potential energy surface at the B3LYP/LANL2DZ/def2-SVP/COSMO level. The Pt-195 NMR chemical shift was calculated at the DFT-Functional-DKFull/NMR-DKH/COSMO, where the functionals BP86, PBE, BLYP, PBE0, and B3LYP were tested. All calculations were carried out in NWCHEM 7.0.0 program. From the calculated results, it can be observed that the pure GGA functionals showing a better performance when compared to the hybrid functional. The best result was obtained at the BLYP-DKFull/NMR-DKH/COSMO level, where a DAM and DRM of only 34 ppm and 1.6% was found.