Spin states of multielectron systems and the action of multi-spin bans

Magnetic and spin effects in chemical reactions are caused by the effect of spin bans, which control the elementary acts of radical and ion-radical reactions involving, as a rule, two paramagnetic particles. Any description of spin bans acting in chemical and enzymatic reactions, which is accompanied by transfer of several electrons, as well as in the reactions of high spin molecules, requires knowledge of spin states. It is shown that spin states of multi-electron states should be described by a spin density matrix; rules for their construction are given and their properties are described. As a first step, the construction of four-density matrix is described in detail. The application of four- and three-spin density matrixes is shown for analyzing the formation of superoxide anion in respiratory chains of mitochondria.