On stretch of approximately thirty years the Electronic Paramagnetic Resonance (EPR) remains to one of main research techniques in chemistry of coordination compounds containing paramagnetic ions of transitional metals. Observing modifications in spectrums at introduction in a system it is possible to judge any reagent or variation of exterior requirements, character of flowing past processes and to identify yields even without their selection from a reactionary medium.
    Because of manifold effects of a EPR line of complexes frequently enlarged also are superimposed among themselves. The complexes seldom manage to be gained as large magnetic - dilutes of monocrystals, which besides strictly speaking are not junctions. Therefore in basic the dusts, pool and frozen solutions are studied, which spectrums are easier for removing, but it is more difficult to interpete, than spectrums of monocrystals. At a research of homogeneous processes in solutions this approach generally does not have alternative. At last, in practically important researches on a kinetics and thermodynamics of a complexing the plants as a rule represent a mixture of several paramagnetic yields, that complicates interpretation of EPR-spectrums even more.
    The most effective approach permitting to overcome indicated difficulties, is the mode grounded on direct comparison of experimental spectrums with theoretical. If the experimental spectrum contains many details, and the number of parameters is not too great, the good consent is reliable measure of a regularity of selected model and its parameters.