A. L. Buchachenko

Polyferroorganosiloxanes as catalysts of oxidation processes

Polyferroorganosiloxanes were studied as catalysts for homogeneous oxidation of alkanes by hydrogen peroxide tinder mild conditions. In the oxidation of cyclohexane the catalysts are characterized by high efficiency (conversion of hydrogen peroxide is 25%) and stability Kip to 80 cycles per gat NJ The min product of the oxidation W do presence a 2,4,6-tri-tert-btitylphenol is cyclohexanol (tip to 35% per H2O2).

Magnetic properties of metal oxide clusters linked by flexible chain siloxane fragments

Oligomeric copperdiorganosiloxanes differing in organic environment at the silicon atoms and in the Si/Cu ratio were synthesized. The magnetic properties of all compounds were shown to deviate from the Curie law. Unlike rigid chain oligomers characterized by antiferromagnetic interaction, coordination metal oxide clusters linked by flexible chain siloxane fragments exhibit ferromagnetic properties.

TUNNELING SPECTROSCOPY OF SINGLE ELECTRON SPIN

The possibility of detection of the electron spin of a single paramagnetic species (an atom, a radical, or an ion) on the surface was discussed. The analysis was based on spin chemistry laws taking into account the statistics of the spin states of both the tunneling electron and paramagnetic center. The equations for the tunneling current as a function of temperature and magnetic field strength were derived.

Spin catalysis: dynamics of three-spin systems

The kinetic theory of a new phenomenon, spin catalysis, has been developed. This phenomenon takes place in three-spin systems, when the third radical (or a paramagnetic ion) induces spin conversion in the pair, removes spin forbiddance, and thus changes the reactivity of the first two radicals. Kinetic equations for yields of spin catalyzed reactions have been derived. Conditions for spin catalysis, values of the catalytic effect, and the kinetic behavior are discussed. A new kind of quantum beats in chemical reactions is predicted.

A new nuclear spin selective reaction of molecular oxygen

During high-temperature (623–673 K) oxidation of polyarylenes (polypyromellitimide and polyphenylquinoxaline), the molecular oxygen is enriched in the18O nonmagnetic isotope and impoverished in the17O magnetic isotope. The isotope selection increases with the increase in the degree of conversion of oxygen. The spin-selective reaction responsible for the selection of the17O isotope is the addition of molecular oxygen to triplet exited aromatic fragments of macromolecules to give endoperoxides. This reaction, which is selective in terms of the electron spin, is also nuclear-spin selective resulting in a magnetic isotope effect. The selection of nonmagnetic isotopes,16O and18O, is caused by competition between the reversible and irreversible decomposition of endoperoxide and by the classical isotope effect in these reactions.

Magnetic isotope effect in the photochemical reduction of uranyl nitrate

A magnetic isotope effect was found in the photochemical reduction of uranyl nitrate by p-methoxyphenol. The initial238U/235U ratio equal to 8.93±0.008 was altered during the reaction to 8.945±0.008-8.970±0.005 in the reaction product, namely, uranium tetrafluoride.

Experimental testing of molecular dynamic functions of pairs by the isotope selectivity of radical recombination

A method for experimental testing of the molecular dynamic functionf(t), which describes the generation of reencounters in a dynamic pair of molecular particles, has been developed. The method is based on the analysis of isotope separation in spin selective reactions of a radical pair. Thef(t) function derived from the solution of the diffusion equation with physically rigorous initial and boundary conditions describes experimental results much better than the well-known Noyes function. Conditions that make it possible to increase the efficiency of isotope separation in spin selective reactions are formulated.