Trinuclear copper(ii) bromide complex [C₃H₅N₃Br]_{2: n}[Cu₃Br₈]_n. Structure, magnetic properties and DFT calculations

Halidocuprates(ii) show unusual magnetic properties and a high degree of structural flexibility. We present the results of crystallographic, electron paramagnetic resonance (EPR) spectroscopic and magnetochemical analyses of a new [HL]_2n[Cu₃Br₈]_n compound (HL = 3-amino-4-bromopyrazolium)-the first example of an inorganic polymer built from trimeric [Cu₃Br₈]^2- units with a 5-membered nitrogen-containing heterocycle as an organic counter ion. The EPR spectrum of the polycrystalline sample exhibited a signal at g ≅ 2.06 broadened owing to spin-spin interactions between copper ions. The EPR and magnetochemical data indicate a ferromagnetic intertrimer interaction with Θ = 13 K and an antiferromagnetic intratrimer interaction with J = 310 K between the nearest-neighbor copper(ii) ions, which is in agreement with DFT calculations.