The Role of Singlet and Triplet Dioxygen Molecules in the EPR and 1H NMR Spectrum Line Broadening

In the Mo^(VI)/H₂O₂/H₂O system, the relaxation time (T ₁) of protons in a water molecule and in a CH₃ group decreases 10 to 30 times under conditions of dismutation of H₂O₂ with the formation of ¹O₂(¹_g). It is experimentally found that the overequilibrium concentration of triplet dioxygen cannot be the reason behind a decrease in T ₁ in the ¹H NMR spectra. Neither can it explain the anomalous line broadening in ESR spectra under conditions of ¹O₂(¹_g) formation in the systems V^(V)/H₂O₂/AcOH and Mo^(VI)/H₂O₂/H₂O. Ab initio calculations showed that it is principle possible that the ³O₄(³·^- _g-¹_g) molecule exists in a snake-like form and is formed by the reaction between ³O₂(³·^- _g) and ¹O₂(¹_g), which is the product of H₂O₂ decomposition in the systems V^(V)/H₂O₂/AcOH and Mo^(IV)/H₂O₂/H₂O. The interaction of ¹O₂ with the ·OOH radical is exothermic (Q = 2.30 kcal/mol) and leads to the formation of ·OOOOH. It is assumed that the paramagnetic species of type ·OOOOH or ³O₄(³ A ₁) that is formed in the reaction might be responsible for the spectral effects observed.     

Regioselectivity of acid-catalyzed cyclization of 1-(3,4-dialkylaryl)-3-chloropropan-1-ones to indanones. Comparison of experimental data and results of computer simulation

The acid-catalyzed cyclization of 1-(3,4-dialkylaryl)-3-chloropropan-1-ones to dialkylindanones via the intermediate formation of (3,4-dialkylaryl)propenones was studied. This reaction affords isomeric products: 5,6-dialkylindan-1-ones and 4,5-dialkylindan-1-ones. The DFT quantum chemical calculation results correlate with the experimental data and suggest that the structural factors affect the ratio of products.     

Catalytic reactions of hydrocarbons promoted by coordination unsaturated Zr and Ti compounds: A density functional theory study

The paper is a review of a series of publications devoted to a number of homogeneous and heterogeneous catalytic reactions, their mechanisms, and energy characteristics. These reactions are promoted by coordination unsaturated compounds of Ti and Zr and proceed with cleavage and/or formation of C-C and C-H bonds in the hydrocarbon chain (polymerization reaction of ethylene, styrene, and butadiene-1,3, hydrogenolysis and hydroisomerization of linear and branched alkanes, and H/D isotope exchange in alkanes). A high-level quantum chemical method (DFT, PBE functional, gauss type TZ2p basis sets, the original PRIRODA program) was applied for the catalytic systems under the study. The nature and the structure of the active center, detailed mechanisms, and energy profile of the reaction of the substrate with a catalytic particle are considered. We compare our data with the results of both experimental and theoretical contributions from other authors.     

Primary isotopic effect on the magnetic shielding of tin nuclei (117Sn and 119Sn)

The Kirkwood-Buff statistical mechanical theory of surface tension γ for monatomic fluids is extended to molecular fluids. A rigorous expression for γ is derived in terms of the angular pair distribution function f(z ₁ R ₁₂θ₁θ₂) of an equilibrium fluid-fluid system (liquid-gas, liquid-liquid, or gas-gas). The Fowler approximation is applied for the liquid-gas case, and a simple expression for γ is derived in terms of the bulk liquid angular pair correlation function g(R ₁₂θ₁θ₂). Thermodynamic perturbation theory for g(R ₁₂θ₁θ₂) is also used to calculate γ theoretically. The theoretical results are compared with experimental values.     

Redox induced reactions of transition metal π- and σ,π-complexes

In this review, redox-induced reactions of π- and σ,π-complexes leading to the selective formation (or cleavage) of C–H, C–C, and C–O bonds have been summarized. To illustrate the synthetic potential of such methodology, the following representative reactions studied in our group are discussed: (1) oxidatively induced hydrogen elimination from “open” cyclic diene and dienyl complexes resulting in formation of “closed” dienyl and arene complexes, respectively; (2) reductive activation of C–H bonds in diene, vinylidene, and carbyne complexes forming new multiple C–C bonds; (3) oxidative dehydrodimerization of vinylidene complexes into binuclear μ-divinylidene species; and (4) oxidatively induced addition of oxygen nucleophiles to μ-divinylidene complexes affording cyclic μ-dicarbene derivatives. Oleg V. Gusev, deceased on October 31.