On the Magnetic Properties of Systems with Low Dimensional Linkage of VO ₅ Pyramids

[N(CH3)(4)]V3O7, (en)(2)ZnV6O14 (en=ethylenediamine) and (C6H14N2)V6O14. H2O With edge-sharing VO5 chains have been prepared hydrothermally and studied by magnetic susceptibility measurements and by NMR. Observed magnetic properties, which indicate the existence of the spin gap; can be explained by a model of isolated spin dimers of V4+ ions, where a very large exchange interaction J exists only between the electrons at V sites within two edge-sharing VO5 pyramids whose apical oxygens are on the same side of the basal planes. It can be understood by considering the kinetic exchange mechanism acting between the electrons in the xy orbitals.