An. M. Kuznetsov

Quantum chemical model of solvation for calculation of electrode potentials of redox processes involving ferrocene, cobaltocene, and their ions

Quantum chemical calculations of solvation energy for ferrocene and cobaltocene molecules and their ionic forms in water, acetonitrile, methanol, and acetone are performed in terms of the B3LYP density functional method by taking into account solvation effects and using the polarized continuum model (PCM). Standard electrode potentials of the corresponding redox pairs, the effect of solvent on them, and the overall energy of the transfer of cobaltocene cation and anion between two solvents are calculated. The calculation results well agree with the available experimental data. The present study provides sufficiently reliable grounds for the application of an ion—metallocene molecule redox pair as a pilot system for the comparison of electrode potentials and solvation energies in different solvents.

Quantum-chemical investigation of the formation of Lewis acid centers of high-siliceous zeolites

AM1 quantum-chemical model calcualtions of the dealumination process in high-siliceous zeolites have confirmed the thermodynamical possibility of Lewis center formation mechanism previously suggested by other authors. The structure and local charge distribution for the Lewis centers of two arts produced at this process were studied in detail. The calculated values of the NH3 and CO adsorption energies on these L-centers allowed for conclusion about their relative acidity.

Electronic charge density transfer along a constrained reaction path from a hydronium ion configuration into a hydrogen chemisorption state on Cu(100)

Abstract On supermolecular models of a hydrogen reaction intermediate on Cu(100), we have investigated structural transformations and electronic charge density transfer along a constrained proton transfer path from a hydrated hydronium ion configuration into a H(ad) state. Computations were carried out on MP2 level on closed shell model systems Cu 9 /H 5 O 2 and Cu 9 /H 9 O 4 , using Gaussian (3s2p5d) valence basis set and ECPs for Cu, and DZP(d,p) for O and H atoms. A charge transfer from initial to final adsorbate state respectively from +1 to a significantly negative value, and coupled nuclear motion patterns including water reorientations near H(ad) have been proved under 2D-freedom of the constrained reaction path.

Solvation of ferrocene, cobaltocene, and their ions by the data of quantum-chemical calculations

Quantum-chemical calculations of solvation energy for ferrocene and cobaltocene molecules and their ionic forms in water, acetonitrile, methanol, acetone, and dimethylsulfoxide are performed in terms of the density functional method of the B3LYP type, taking into account the effect of solvent and using the Polarized Continuum Model (PCM). It is shown that the optimization of metallocene structure in liquid introduces only slight quantitative changes as compared with the data calculated for the structures optimized in the gas phase. It is shown that earlier observed deviation of experimental redox potentials of cobaltocene system in dimethylsulfoxide from the regularities of continuum electrostatics is caused by a stronger effect of this solvent on the distribution of electron density over the molecule of dissolved substance.

Molecular–Continuum Model for the Cyanide Ion Adsorption from Aqueous Solutions on Copper Metals

Quantum-chemical calculations of the cyanide ion adsorption from aqueous solutions on copper metals are performed for the first time in a combined molecular–continuum model of polar solvent. The calculations use the cluster model of the surface and are carried out by the density functional in the B3LYP version. The effect of the adsorption systems polar dielectric environment is considered in a self-consistent reactive field model, namely, the SCIPCM model. The dielectric cavity is built in SCIPCM self-consistently with the particles electron density distribution in solution. Calculations show that the CN– adsorption energy decreases in the sequence Au > Cu > Ag. The calculated energy agrees best with the experimental data when the molecular–continuum model is used, rather than the simpler molecular and continuum models.

Quantum-chemical Calculation of Standard Redox Potentials of Half-reactions Involving Bismuth Aquacomplexes

The most probable coordination numbers for aquacomplexes of Bi(III), Bi(II), and Bi(I) ions are found in terms of a density functional method (version B3LYP) with allowance for the effect of dielectric medium in the self-consistent reaction field model. Thermodynamic parameters of hydration of these ions are calculated and used for evaluating standard redox potentials of half-reactions involving the ions.

Quantum-Chemical Study of Electroreduction Mechanism of Copper(I) Cyanide Complexes

Mechanism of electroreduction of copper(I) cyanide complexes from aqueous electrolytic solutions is studied within a quantum-chemical method of a density functional and a quantum-mechanical theory of charge transfer in polar environment. The electrochemically active form directly participating in an elementary electroreduction act is shown to be the [Cu(CN)2]– complex. Modeling calculations of the activation energy for an elementary charge transfer act reveal for the first time that the transfer of heavy particles along an adiabatic potential energy curve is a more probable mechanism of electroreduction of copper(I) cyanocomplexes than an outer-sphere electron transfer.

Electroreduction of Zn(II) Hydroxy-complexes in Aqueous Electrolytes: A Quantum-chemical Study

The quantum-mechanical theory of the charge transfer in polar media is used to demonstrate that, despite the predominance of high-coordinated Zn(II) hydroxy-complexes in electrolyte, their discharge is preceded by a ligand abstraction stage with the formation of neutral species [Zn(OH)2], which theoretically substantiates experimental facts.

Molecular–Continuum Model for Calculating Chemical Hydration Enthalpy of the Cyanide Ion

Structures of hydrate complexes (H2O)xCN–(H2O)y , where x + y = 1–5 are optimized by the density functional method in the B3LYP version. It is shown that the nearest hydration sphere of the cyanide ion comprises four water molecules directly linked to the ion by hydrogen bonds. The chemical enthalpy of the hydration of the cyanide ion is calculated in the reactive-field continuum models (PCM and SCIPCM) and in other nonelectrostatic interactions. The calculation takes into account the electrostatic interaction between the hydrate complex and the solvents dielectric surrounding. Calculation results are in good agreement with experiment.

Inclusion compounds based on nickel(II) dimethylglyoxymate and cucurbit[8]uril: A quantum chemical prediction of the structure and thermodynamic parameters of formation

Within density functional theory the structure of an inclusion compound based on Ni(II) dimethylglyoxymate and the macrocyclic cucurbit[8]uril nanocavitand is investigated and the thermodynamic parameters of its formation are estimated. Based on the results obtained a prediction is made about the principal possibility of the synthesis of this inclusion compound.