Spin Frustrated Pyrazolato Triangular Cu^II Complex: Structure and Magnetic Properties, an Overview

The synthesis and structural characterization of a new triangular Cu₃–μ₃OH pyrazolato complex of formula, [Cu₃(μ₃−OH)(pz)₃(Hpz)₃][BF₄]₂ (1−Cu₃), Hpz = pyrazole, is presented. The triangular unit forms a quasi-isosceles triangle with Cu–Cu distances of 3.3739(9), 3.3571(9), and 3.370(1) Å. This complex is isostructural to the hexanuclear complex [Cu₃(μ₃−OH)(pz)₃(Hpz)₃](ClO₄)₂]₂ (QOPJIP). A comparative structural analysis with other reported triangular Cu₃–μ₃OH pyrazolato complexes has been carried out, showing that, depending on the pyrazolato derivative, an auxiliary ligand or counter-anion can affect the nuclearity and/or the dimensionality of the system. The magnetic properties of 1−Cu₃ are analyzed using experimental data and DFT calculation. A detailed analysis was performed on the magnetic properties, comparing experimental and theoretical data of other molecular triangular Cu₃–μ₃OH complexes, showing that the displacement of the μ₃−OH⁻ from the Cu₃ plane, together with the type of organic ligands, influences the nature of the magnetic exchange interaction between the spin-carrier centers, since it affects the overlap of the magnetic orbitals involved in the exchange pathways. Finally, a detailed comparison of the magnetic properties of 1−Cu₃ and QOPJIP was carried out, which allowed us to understand the differences in their magnetic properties.