Quantum mechanical study on the mechanism and kinetics of the cis-to-trans isomerization of [Pd(C6Cl2F3)I(PH3)2]

Quantum Mechanical Study of γ-Fe2O3 Nanoparticle as a Nanocarrier for Anticancer Drug Delivery

Using density functional theory (DFT), noncovalent interactions and four mechanisms of covalent functionalization of melphalan anticancer drug onto γ-Fe2O3 nanoparticles have been studied. Quantum molecular descriptors of noncovalent configurations were investigated. It was specified that binding of melphalan onto γ-Fe2O3 nanoparticles is thermodynamically suitable. Hardness and the gap of energy between LUMO and HOMO of melphalan are higher than the noncovalent configurations, showing the reactivity of drug increases in the presence of γ-Fe2O3 nanoparticles. Melphalan can bond to γ-Fe2O3 nanoparticles through NH2 (k 1 mechanism), OH (k 2 mechanism), C=O (k 3 mechanism) and Cl (k 4 mechanism) groups. The activation energies, the activation enthalpies and the activation Gibbs free energies of these reactions were calculated. Thermodynamic data indicate that k 3 mechanism is exothermic and spontaneous and can take place at room temperature. These results could be generalized to other similar drugs.

Density Functional Theoretical Study on the Mechanism of Alcoholysis of Acylpalladium(II) Complexes

The mechanism of alcoholysis of acylpalladium(II) complexes relevant to the alternating copolymerisation of ethene and carbon monoxide has been investigated theoretically in detail. The solvolysis of acylpalladium(II) complexes is an important step in palladium-catalysed reactions. Based on experimental studies, two mechanisms have been proposed for this process, which consist of a concerted reductive elimination and an insertion mechanism (reductive elimination via a Meisenheimer intermediate). Both mechanisms include deprotonating of an acylpalladium(II) complex and according to our calculations, any mechanism involving this step, has an energy barrier higher than that of the rate-determining step. We propose a new mechanism for the insertion in which proton transfer to Pd is simultaneous with an inner-sphere attack of the alkoxide ligand (OCH3) at the carbon atom of the palladium-bound carbonyl group (new Meisenheimer intermediate). Considering solvent effects, the activation energies of the two mechanisms and other contingent mechanisms were calculated and compared with each other and the experimental results.

Theoretical Study on the Mechanism of Covalent Bonding of Dapsone onto Functionalised Carbon Nanotubes: Effects of Coupling Agent

Using density functional theory, two mechanisms of covalent bonding of dapsone onto functionalised carbon nanotubes have been investigated, the first one being direct bonding and the second one being bonding by using coupling agents. In this work, the mechanism of functioning of an important coupling agent (1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo [4,5-b]pyridinium 3-oxide hexafluorophosphate, N-HATU) has been investigated. The activation energy and activation Gibbs free energy of the two pathways have been calculated and compared with each other. It was found that using the coupling agents will reduce the energy barrier. All of the calculations have been performed in the solution phase (polarised continuum model) using the B3YLP hybrid density functional.

Mechanism of covalent adsorption of benzenesulfonamide onto COOH– and COCl– functionalised carbon nanotubes

Using density functional theory, two mechanisms of covalent adsorption of benzenesulfonamide in water in the presence of functionalised carbon nanotubes were investigated. COOH– and COCl–functionalised carbon nanotubes can bond to the benzenesulfonamide via OH (OH pathway) and Cl (Cl pathway) groups, respectively. The activation energy and activation Gibbs free energy of the two pathways have been calculated and compared with each other. It was found that the OH pathway has an energy barrier higher than the Cl pathway and, in contrast to the Cl pathway, product formation is endothermic and non-spontaneous, being thus the reason for the dominance of the Cl pathway. All the calculations were performed using a hybrid density functional method (B3LYP) in the solution phase (polarised continuum model or PCM).

Quantum mechanical study on the different fluxional mechanisms in a [Pd(η2-olefin) complex

In this work, using quantum mechanics, different fluxional mechanisms in a Pd(η2-olefin) complex including sulfur inversion, olefin pseudo rotation, Pd–olefin bond dissociation, propeller-like olefin rotation and a bimolecular process have been investigated theoretically in a solvent environment using the polarisable continuum model (PCM). The activation energy, activation enthalpy and activation Gibbs free energy of the different pathways have been calculated and compared with each other and with experimental results. These activation energies for olefin pseudo rotation, Pd–olefin bond dissociation and propeller-like olefin rotation are greater in comparison with those for the sulfur inversion and bimolecular process, which demonstrates that these latter mechanisms are the dominating paths and make the main contributions in the reaction. The computed activation enthalpies of the sulfur inversion and bimolecular process pathways are in good agreement with the experimental values. All of the calculations have been performed using a hybrid density functional method (B3LYP) in the solution phase.

Density Functional Theoretical Study on the Mechanism of Adsorption of 2-Chlorophenol from Water Using γ-Fe2O3 Nanoparticles

Using density functional theory, the mechanism of adsorption of 2-chlorophenol from water in the presence of γ-Fe2O3 nanoparticles was investigated. Fe2O3 nanoparticles were modelled using Fe6(OH)18(H2O)6 ring clusters. 2-chlorophenol can coordinate to the γ-Fe2O3 nanoparticles via its own OH or Cl groups. The process produces two intermediates which will be converted into final products through two pathways (Cl pathway and OH pathway). The activation energy and activation Gibbs free energy of the two pathways have been calculated and compared with each other. It was found that the OH pathway is under thermodynamic control and the C1 pathway is under kinetic control. All of the calculations were performed using a hybrid density functional method (B3LYP) in the solution phase (PCM model).

Quantum Mechanical Study on the Rate Determining Steps of the Reaction between 2-aminopyrimidine with Dichloro-[1-methyl-2-(naphthylazo) Imidazole] Palladium(II) Complex

In this work, using quantum mechanics, the mechanism of reaction between 2-aminopyrimidine with dichloro-[1-methyl-2-(naphthylazo) imidazole] palladium(II) complex was investigated. The reaction produces two five-coordinated intermediates which are converted into final products through two possible pathways (nucleophile-dependent pathway and solvent-dependent pathway). The activation energy and activation Gibbs free energy of two pathways have been calculated and compared with each other and experimental results. These activation energies for the solvent-dependent pathway are greater in comparison with the nucleophile-dependent pathway which demonstrates that the latter is the dominating route and makes the main contribution to the reaction. Considering solvent effects, the activation Gibbs free energy for the rate determining step of the nucleophile-dependent pathway was calculated, which was in good agreement with the experimental value. Although the theoretical activation energy shows a suitable behaviour qualitatively, it is not fully consistent with the experimental value. All of the calculations were performed using a hybrid density functional method (B3LYP) in the solution phase (PCM model).

Theoretical and Experimental Studies on the Regioselectivity of Epoxide Ring Opening by Nucleophiles in Nitromethane without any Catalyst: Nucleophilic-Chain Attack Mechanism

We describe here a mild and efficient method for the nucleophilic ring-opening of epoxides with amines, alcohols and water in the presence of nitromethane as a polar solvent without using any catalyst. The reactions are highly regioselective and afford the products in excellent yields within a short period of time at room temperature. The regioselectivity for this ring opening has been investigated using experimental and theoretical 1H and 13C NMR studies together with activation energy calculations at the B3LYP/6-311+G(2d,p) level of theory. The mechanism of nucleophilic attack has been investigated in terms of a direct attack or a methanol chain attack.