Tetrabromidocuprate(II) complexes with diprotonated 1-hydroxy-4me-thyl-2-(pyridin-2-yl)-5-phenylimidazole and 1-hydroxy-2-(pyridi-n-2-yl)-4,5,6,7-tetrahydrobenzimidazole ligands: Relationship between the structure and magnetic properties

Two new tetrabromidocuprate(II) complexes with diprotonated 1-hydroxy-2-(pyridin-2-yl)-4,5,6,7-tetrahydro-benzimidazole (1) and 1-hydroxy-4methyl-2-(pyridin-2-yl)-5-phenylimidazole (2) were synthesized and their structure established from single-crystal X-ray data. Compounds crystallized in the monoclinic space groups P21/ n and P21/c, respectively, where tetrabromidocuprate anions formed magnetic chains as inferred from the dis-tances between the halide ions of different [CuBr4]2 � units. Magnetization measurements showed that both compounds behave as well-isolated uniform S = 1/2 antiferromagnetic chains described by the one-dimensional Heisenberg antiferromagnetic model with intra-chain exchange interaction 2 J = 23 K (1) and 2 J = 33 K (2) (the Hamiltonian H = 2J n-ary sumation S i theory investigations provided complementa r y results for 1 and 2. A calculation of exchange coupling constants gave values of 2 J = 24 K (1) and 2 J = 39 K (2), in good agreement with the experiment. The quantu m theor y of atoms in molecules and non-covalent interaction analyses showed that halogen bonding determined the ex-change interaction between [CuBr4] 2 � units in magnetic chains of these cation-anion compounds. Si+1). Electron paramagnetic resonance, optical absorption, and density functional