Synthesis, structures, and magnetic behavior of new anionic copper(II) sulfate aggregates and chains

Andrew D Burrows, M.F. Mahon, V.M. Sebestyen, Y. Lan, A.K. Powell

OAI: oai:purehost.bath.ac.uk:publications/cea6891c-35ee-4d79-8038-1c5df055a54d • DOI: https://doi.org/10.1021/ic301478x

The reaction between CuSO 4·5H 2O and [NMe 2H 2]Cl in N,N-dimethylformamide (DMF) at 95 °C yielded green crystals of (NMe 2H 2) 4[Cu 6O 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 2H 2]Cl, yellow-green crystals of (NMe 2H 2) 4[Cu 6O 2(SO 4) 6(DMF) 2] 2 were obtained. The anions in 2 contain similar Cu 6O 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 6O 2(SO 4) 6 aggregates observed in 1 and 2 are related to those present in the rare copper sulfate mineral fedotovite, K 2Cu 3O(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 2O and [NMe 2H 2]Cl in DMF at room temperature gave (NMe 2H 2)[Cu 2(OH)(SO 4) 2(H 2O) 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.