Crystal structures and magnetism of infinite alternating chains arranged by paddle-wheel dinuclear copper and mononuclear copper units

Abstract

The crystal structures and magnetic properties of two novel polyclusters {[Cu₃(tci)₂(H₂O)₂]·12H₂O}_n (1) and {[Cu₃(tci)₂(H₂O)₂]·6H₂O}_n (2) (tci = tris(2-carboxyethyl) isocyanurate) are investigated. The X-ray crystallographic analysis reveals that they contain interesting infinite alternating chains of dinuclear paddle-wheel copper and mononuclear copper units arranged in ABBA magnetism exchange mode. Variable-temperature magnetic susceptibility measurements on the two polyclusters show strong antiferromagnetism couplings between copper ions with exchange interactions J = −181.4 cm⁻¹, zj′ = −0.31 cm⁻¹ for 1, J = −170 cm⁻¹, zj′ = −0.42 cm⁻¹ for 2. With the aim of studying magneto-structural correlation, we synthesized a three-dimensional polymer [Cu₃(tci)₂(py)₄(H₂O)₂]_n (3) based on isolated dinuclear cluster and mononuclear copper units. Fitting the susceptibility data yielded J = −176.1 cm⁻¹, zj′ = −0.084 cm⁻¹ for 3.