Аннотация:This article is a short overview of the problem of controllable magnetic spin communicationas an important ingredient of spintronics and molecular electronics. We discuss the problem of communicationof the two localized spins mediated by the mobile electron which is shared between twonon-magnetic sites coupled to the mobile spins. The model system which is assumed to mimic the keyfeatures of spin communication has a tetrameric linear structure with two terminal spins connected viathe central mixed-valence (MV) dimeric unit. We propose a “toy” model which is expected to describethe exchange coupling between the localized spins mediated by the itinerant electron in complex systemssuch as reduced polyoxometalates hosting metal ions. The proposed model is parametric andintentionally simplified in order to give a qualitative insight on a wide class of the systems bearing inmind the main physical phenomena and at the same time avoiding analysis of their specific details.The model takes into account the following interactions peculiar for complex systems: electron transferin the MV moiety, magnetic exchange between the localized spins and the delocalized electrons,coupling of delocalized electron with molecular vibrations and interaction of the system with an externalelectric field. The aim of the model is to describe in a parametric way a series of compounds withpartially delocalized electrons with minimal number of the fitting parameters that reflect the mainphysical features of complex systems. To make the conclusions imaginative we discuss the limitingcases in details. In the case of relatively strong exchange coupling the combined action of the namedinteractions is shown to give rise to a specific kind of double exchange coupling termed here “externalcore” double exchange. In the opposite case of relatively strong electron transfer we arrive to an effectiveindirect exchange. A possibility to control the coupling between the localized spins by the externalelectric field acting on the mobile electron is discussed. It is demonstrated that the effect of the electricfield on the strength of spin communication is amplified by the vibronic coupling so that this couplingdecreases the value of the field required for a tangible control of the strength of spin communication.In the presentation of the problem we sought to emphasize the main concepts in a qualitative waycleared of mathematical details addressing the review, that we referrer as tutorial, to a wide audienceof the readers: chemists, physicists and specialists in materials science.