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Article

Synthesis, Structure, and Magnetic Properties of the Layered Copper(II) Oxide Na₂Cu₂TeO₆

Supporting Info

Jianxiao Xu,^† Abdeljalil Assoud,^† Navid Soheilnia,^† Shahab Derakhshan,^† Heather L. Cuthbert,^‡ John E. Greedan,^‡ Mike H. Whangbo,^§ and Holger Kleinke*^†

Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1, Department of Chemistry and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada L8S 4M1, and Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204

Inorg. Chem., 2005, 44 (14), pp 5042–5046

DOI: 10.1021/ic0502832

Publication Date (Web): June 3, 2005

Abstract

A new quaternary layered transition-metal oxide, Na₂Cu₂TeO₆, has been synthesized under air using stoichiometric (with respect to the cationic elements) mixtures of Na₂CO₃, CuO, and TeO₂. Na₂Cu₂TeO₆ crystallizes in the monoclinic space group C2/m with a = 5.7059(6) Å, b = 8.6751(9) Å, c = 5.9380(6) Å, β = 113.740(2)°, V = 269.05(5) Å³, and Z = 2, as determined by single-crystal X-ray diffraction. The structure is composed of [Cu₂TeO₆] layers with the Na atoms located in the octahedral voids between the layers. Na₂Cu₂TeO₆ is a green nonmetallic compound, in agreement with the electronic structure calculation and electrical resistance measurement. The magnetic susceptibility shows Curie−Weiss behavior between 300 and 600 K with an effective moment of 1.85(2) μ_B/Cu^II and _c = −87(6) K. A broad maximum at 160 K is interpreted as arising from short-range one-dimensional antiferromagnetic correlations. With the aid of the technique of magnetic dimers, the short-range order was analyzed in terms of an alternating chain model, with the surprising result that the stronger intrachain coupling involves a super-superexchange pathway with a Cu−Cu separation of >5 Å. The J₂/J₁ ratio within the alternating chain refined to 0.10(1), and the spin gap is estimated to be 127 K.