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Subject classification: 13; 22.9 Institute of Chemistry, Academy of Sciences of the Moldavian SSR, Kishinev On the Insufficiency of the Heisenberg Model of Exchange Interaction for Polynuclear Clusters BY B.S. TSUKERBLAT, M. I. BELINSKII, and A . V. ABLOV At present there is no rigorously substantiated framework of the applicability of the Heisenberg-Dirac-Van Vleck (HDVV) Hamiltonian (1) to polynuclear many-electronio systems. On the other hand a great number of experiments cannot be explained on the base of the HDVV model. As a striking instance crystals containing 3* [ Cr30(CH2COO)6(H20)~+-type clusjers with three octahedrally coordinated C r ions in the corners of on equilateral triangle can be mentioned (1 to 7). The antiferromagnetic intramolecular interaction fi = J spin degeneracy, however the energy levels of thz states with the same total spins (2D (ll2), 4D(3'2) etc.) coincide (Fig. la) in contrast with the experimental data on the temperature dependence of heat capacity C(T) , the magnetic susceptibility (3 to 6) being indicative of the splitting of the ground and excited states. The numerous attempts to interpret the experimental data by introducing the additional exchange parameter J 3 8 (3, 5, 6), should be admitted to be incorrect because they contradict the X-ray data (2, 4). In the present note we show that to explain the above mentioned experiments one does not demand the complicate HDW model 3. S. (S = 3/2) removes the 64-fold 0.. 1 J A

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Aus schwach salpetersaurer methanolischer Cwnitrat‐Lösung läßt sich mit SalicylaldehydSelenosemicarbazon das komplexe Nitrat (I) fällen.