Chemical polarization of nuclei in reactions of photoreduction of benzophenone and the effect of a heavy atom

Abstract

1. Restriction of molecular mobility by increasing the viscosity of the medium or including a radical pair (RP) in a micelle is manifested by a significant increase in the polarization amplification factors in comparison to polarization in the same systems in a nonviscous solvent. Restriction of molecular mobility results in an increase in the fraction of RP in which selection can take place with respect to the nuclear spins, and thus in an increase in polarization. 2. Incorporation of a heavy Br atom in the structure of the donor or acceptor results in a decrease in the effects of an external magnetic field and in most cases a decrease in the amplification factors of the PMR lines of the polarized products of the photochemical redox reaction. The cause of this consists of the appearance of a spin-orbital interaction between the radicals in the contact RP. 3. Restriction of molecular mobility for systems with heavy atoms results in a significant decrease in polarization in comparison to polarization in a nonviscous homogeneous solvent. The RP remains in contact for a longer time in a viscous medium or micelle, and the spin-orbital interaction can significantly reduce the spin correlation of the RP, which is also reflected in the low amplification factors.