Exchange interaction in polynuclear complexes. Part 3. Experimental study and theoretical interpretation of the antiferromagnetic coupling in di-µ-oxo-octaoxodichromate(III); comparison with tri-µ-chloro-hexachlorodichromate(III)

Abstract

The temperature dependence of the magnetic susceptibility of the new material Cr₂Te₄O₁₁ has been studied in the range 4.2–300 K. The compound contains the binuclear anion [Cr₂O₁₂]^14– as isolated units, resulting from sharing of an edge between two CrO₆ octahedra. The exchange-interaction parameter J of the H.D.V.V. Hamiltonian –JŜ_AŜ_B is equal to –6 ± 0.5 cm^–1. In the framework of a previously described model for the exchange interaction and using the iterative extended-Hückel method, the antiferromagnetic contribution of the exchange interaction has been calculated. A slmllar calculation has been carried out for the binuclear anion [Cr₂Cl₉]^3–. Comparison of the results for both compounds shows that our model leads to the relative magnitude of the exchange interaction in cases of antiferromagnetlc coupling.