Accurate prediction of 195Pt-NMR chemical shifts for hydrolysis products of [PtCl6]2− in acidic and alkaline aqueous solutions by non-relativistic DFT computational protocols

Abstract

The 195Pt-NMR chemical shifts of all possible hydrolysis products of [PtCl6]2− in acidic and alkaline aqueous solutions are calculated employing simple non-relativistic density functional theory computational protocols. Particularly, the GIAO-PBE0/SARC-ZORA(Pt) ∪ 6-31 + G(d)(E) computational protocol augmented with the universal continuum solvation model (SMD) performs the best for calculation of the 195Pt-NMR chemical shifts of the Pt(IV) complexes existing in acidic and alkaline aqueous solutions of [PtCl6]2−. Excellent linear plots of δcalcd(195Pt) chemical shifts versus δexptl(195Pt) chemical shifts and δcalcd(195Pt) versus the natural atomic charge QPt are obtained. Very small changes in the Pt–Cl and Pt–O bond distances of the octahedral [PtCl6]2−, [Pt(OH)6]2−, and [Pt(OH2)6]4+ complexes have significant influence on the computed σiso 195Pt magnetic shielding tensor elements of the anionic [PtCl6]2− and the computed δ 195Pt chemical shifts of [Pt(OH)6]2− and [Pt(OH2)6]4+. An increase of the Pt–Cl and Pt–O bond distances by 0.001 Å (1 mÅ) is accompanied by a downfield shift increment of 17.0, 19.4, and 37.6 ppm mÅ−1, respectively. Counter-anion effects in the case of the highly positive charged complexes drastically improve the accuracy of the calculated 195Pt chemical shifts providing values very close to the experimental ones.