Structural and magnetic properties of quasi-1 and 2D pyrazine-containing spin-1/2 antiferromagnets

Aqueous reaction of Cu(BF4)2, NH4HF2, and pyrazine leads to formation of a novel 3D framework, [Cu(HF2)(pyz)2]BF4 (1), where 2D [Cu(pyz)2]2+ square layers are connected via HF2-. A second compound, Cu(ReO4)2(H2O)2(pyz) (2), was the result of our attempt to create the perrhenate analog of 1; a linear chain compound consisting of CuO4N2 octahedra linked through pyrazine ligands formed instead. Both compounds exhibit extensive hydrogen bonding interactions where bifluoride, F⋯H⋯F−, and O–H⋯O link layers and chains together in 1 and 2, respectively. Broad maxima indicative of short-range magnetic ordering (SRO) were observed in the magnetic susceptibility at 5.5 (1) and 7.7 K (2) while no evidence for the transition to long-range magnetic ordering (LRO) was detected above 2 K.

Graphical abstractTwo new copper(II) coordination polymers are reported. [Cu(HF2)(pyz)2]BF4 (1) consists of a novel 3D framework in which Cu2+ centers are linked by pyrazine and bifluoride ligands. Long-range magnetic ordering occurs below 1.54 K. The second compound, Cu(ReO4)2(H2O)2(pyz) (2) has a linear chain structure and shows a broad maximum in the magnetic susceptibility at 7.7 K while LRO was not observed above 2 K.Figure optionsDownload full-size imageDownload as PowerPoint slide