Synthesis, Structures, And Magnetic Behavior of New Anionic Copper(II) Sulfate Aggregates and Chains

Abstract

The reaction between CuSO(4)·5H(2)O and [NMe(2)H(2)]Cl in N,N'-dimethylformamide (DMF) at 95 °C yielded green crystals of (NMe(2)H(2))(4)[Cu(6)O(2)(SO(4))(6)(DMF)(4)] 1. The discrete [Cu(6)(μ(4)-O)(2)(μ(3)-SO(4))(4)(μ(2)-SO(4))(2)(DMF)(4)](4-) anions present in 1 contain two edge-sharing Cu(4)(μ(4)-O) tetrahedra, with the copper(II) centers bridged by sulfato ligands. These anions are linked into a two-dimensional network through hydrogen bonds involving the dimethylammonium cations. When the reaction was carried out in the absence of [NMe(2)H(2)]Cl, yellow-green crystals of (NMe(2)H(2))(4)[Cu(6)O(2)(SO(4))(6)(DMF)(2)] 2 were obtained. The anions in 2 contain similar Cu(6)O(2)(SO(4))(6) aggregates to those in 1, though these differ in terms of the copper(II) coordination geometries. In addition, the anions in 2 are linked into chains through bridging sulfato ligands. The Cu(6)O(2)(SO(4))(6) aggregates observed in 1 and 2 are related to those present in the rare copper sulfate mineral fedotovite, K(2)Cu(3)O(SO(4))(3), and in common with this mineral both 1 and 2 decompose in the presence of moisture. The reaction between CuSO(4)·5H(2)O and [NMe(2)H(2)]Cl in DMF at room temperature gave (NMe(2)H(2))[Cu(2)(OH)(SO(4))(2)(H(2)O)(2)] 3, the structure of which contains triangular Cu(3)(OH)(SO(4)) units that share vertices to form tapes. Magnetic measurements revealed that 1 and 3 are both spin-canting metamagnetic systems. Field-induced responses were observed below 5 K, with the critical field indicating metamagnetic behavior from antiferromagnetic to ferromagnetic equal to 110 Oe for both compounds.