The platinum complexes with histamine: Pt(II)(Hist)Cl 2, Pt(II)(Iodo-Hist)Cl 2 and Pt(IV)(Hist) 2Cl 2

Abstract

The Pt(II) and Pt(IV) complexes with histamine were calculated by using more than 20 DFT functionals and various basis sets. Based on the comparison between the X-ray and theoretical geometrical parameters of the Pt(II)(Hist)Cl 2 complex the MPW1PW91, OPW91 and SVWN5 functionals combined with the 6-311G ∗∗ basis set for non-metallic and SDD (ECP) basis set for platinum were found to yield the most satisfactory agreement. The structure of the Pt(II) complex with iodohistamine important for pharmacy, so far isolated only in minute amounts, was predicted by using the MPW1PW91 functional. Comparison of the theoretical NMR chemical shifts of the Pt(II)(Hist)Cl 2 complex with those found experimentally have shown that the theoretical 1H and 13C NMR chemical shifts are in plausible agreement with the experimental ones, whereas the theoretical 195Pt chemical shifts fit the experimental values only when the relativistic approach is applied within the ZORA formalism. We confirmed suitability of the three selected functionals for reproduction of the experimental structure of Pt complexes at fourth oxidation state by using the cis- and trans - Pt(IV)(en) 2 Cl 2 2 + ions as models. Finally, with the selected theoretical methods, the structures and stabilities of four Pt(IV)(Hist) 2Cl 2 complex isomers were predicted.