Ligand Exchange in Pd(II)-NaCl-H2O and Pd(II)-HCl-H2O Systems: Quantum-Chemical Consideration

Abstract

The Pd-containing compounds exhibit the biological activity. The variety of the biological properties of the Pd ions and of another platinum-group metals is determined by the chemical and stereochemical properties of coordination compounds of these metals with the biologically active ligands (DNA, amino acids, peptides, etc.) and, in particular, by the structure of the metal-ligand coordination site (fragment or functional group of a biological system) [1]. The Pd(II) complexes with organic ligands are considered to be promising in the production of medicines [2].While studying reactions of the Pd 2+ ion with bioligands, one should take into consideration its interaction with inorganic compounds contained in liquid media of a living organism. It is not improbable that inorganic ligands (H 2 O , Cl -, etc.) can compete with the biologically active ligands for the metal ion and thus reduce toxicity of the latter ion. On the other hand, binding of the metal cation with inorganic ligands can decrease the efficiency of medicines prepared from compounds of this metal. The Pd(II) complexes are known to be bonded by the DNA molecules and to violate ordinary course of the replication process (transcription and translation) [1]. The Pd ( II )-NaCl -H 2 O and Pd ( II )-HCl -H 2 O systems can be used to model the behavior of the Pd(II) compounds in biological liquids. For instance, a 0.86% (0.147 M) solution of NaCl can be used as a model of blood plasma, while a 0.1 M solution of HCl, as that of a gastric juice [3]. The aim of this work was to study the reactions of exchange of the H 2 O and H 3 O + ligands for Cl -in the chloride and hydrogen chloride solutions of Pd(II). EXPERIMENTAL Potassium tetrachloropalladate(II) was synthesized as described in [4] from metallic Pd and Pd ë l 2 . The K 2 [ PdCl 4 ] (0.03067 M) and NaCl (0.1 M) solutions were prepared from the precisely weighed samples; a 0.1 M solution of HCl was prepared from a reagent with fixed concentration.The kinetic studies were carried out using spectrophotometric method. The electronic absorption spectra of the reaction mixtures were recorded on a UV VIS SPECORD spectrophotometer. The working solution of K 2 [ PdCl 4 ] with a concentration of 8.496 × 10 -5 mol/l was prepared by dilution. The initial solution of K 2 [ PdCl 4 ] (3.610 ml) and the solution of 0.1 M NaCl or HCl (20 µ l) were pored into a cell (1 cm) with the aid of a dispenser.The quantum-chemical calculations were performed by ZINDO/1 [5], PM3 [6], and RHF/STO-6G(d) [7] methods with the HyperChem 1 program package and full optimization using the Polak-Ribiere algorithm [8]. The gradient rate did not exceed 0.02 kcal/(mol Å).Abstract -The behavior of potassium tetrachloropalladate(II) in media simulating biological liquids is studied. The rate of aquation in aqueous NaCl solutions is shown to be higher than the rate at which the Cl -ligand enters the inner coordination sphere of the Pd atom. In HCl solutions, the formation of the Pd chloro complexes predominates due to protonation of water molec...

DFT Study of the Monomers and Dimers of 2-Pyrrolidone: Equilibrium Structures, Vibrational, Orbital, Topological, and NBO Analysis of Hydrogen-Bonded Interactions

“…IR and Raman spectroscopic data along with the results of dielectric measurements in different solvents testify the existence of monomer−dimer equilibrium. − The structure of 2-pyrrolidone monomers has been explored extensively by various experimental and theoretical − methods.…”

Determination of the loading and stability of Pd in an arborescent copolymer in ethanol by microplasma-optical emission spectrometry

“…The formation of a chlorohydroxypalladium(II) precipitate has indeed been reported for Pd 2+ at concentrations above 1 ppm, but this was thought to be less predominant at lower Pd concentrations. [56][57][58] Clearly, the solutions used for calibration purposes should be freshly prepared before use.…”

Thermally Induced Dissociation Nature of Pure 2-Pyrrolidinone via Near-Infrared Correlation Spectroscopy Analysis

“…2-Pyrrolidinone is one of the most important solvents in organic synthesis for its outstanding solubility in polar chemicals, which can also be used as ligands for biologically active complexes. 19 Thus, it is essential to carry out a detailed investigation on the hydrogen-bonding behavior of 2-pyrrolidinone in its pure liquid phase, especially under temperature perturbation.…”