SPIN CATALYSIS - ISOTROPIC 4-SPIN MODEL

The spin-exchange mechanism of catalysis of radical reactions and the singlet-triplet conversion of the radical pairs (R(1), R(2)) in isotro pic four-spin triads are theoretically studied. The triad (R(1), R(2), M) is formed from a pair and the spin catalyst M, the ground state of which is triplet with the total spin S = 1 (biradical, triplet molecu le, or paramagnetic ion). S-T conversion of radical pairs is found to be caused by triplet-triplet evolution of the (R(1), R(2), M) triad. I n the case of zero magnetic fields, the spin dynamics and chemical dyn amics of the reactions catalyzed by stable radicals R(3) and triplet s pin catalyst M are shown to be alike.