Crystal Structure and Magnetic Properties of [Cu(4-Me-3-Nit-trz)₄](ClO₄)₂, with 4-Me-3-Nit-trz = 2-(3-[4-Methyl-1,2,4-triazolyl])-4,4,5,5-tetramethylimidazoline-1-oxyl 3-Oxide. Intra- And Intermolecular Spin Interactions

The first two transition metal compounds incorporating triazole-nitronyl- nitroxide radicals as ligands have been synthesized. These compounds are [Cu(4-Me-3-Nit-trz)₄](ClO₄)₂ (1) and [Ni(4-Me-3-Nit-trz)₄](ClO₄)₂ (2) with 4-Me-3-Nit-trz = 2-(3-[4-methyI-1,2,4-triazolyl])-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide. Compound 1 crystallizes in the triclinic system, space group P1̄. The lattice parameters are a = 9.742(2) Å, b = 12.214(12) Å, c = 12.981(4) Å, α = 67.19(4)°, β= 81.48(2)°, and γ = 79.24(4)°, with Z = 1. The structure consists of centrosymmetrical [Cu(4-Me-3-Nit-trz)₄]]²⁺ cations and noncoordinated perchlorate anions. The Cu(II) ion is in an N₄O₂ elongated tetragonal environment with two oxygen atoms of two nitroxide groups occupying the apical positions. Within the lattice the cations form infinite chains with short intermolecular contacts involving the nitronyl-nitroxide moieties of two adjacents cations. The temperature dependence of the magnetic susceptibility and the field dependence of the magnetization at 2 K have been investigated. Both intermolecular antiferromagnetic and intramolecular ferromagnetic interactions are operative. A theoretical model has been developed to interpret quantitatively the magnetic data, which allows us to determine the values of the interaction parameters.