Synthesis, structure, and investigation of unique magnetic properties in two novel Mn-based coordination polymers

Abstract

Two new manganese(II) coordination polymers (CPs) have been synthesized using Mn(SO₄)₂·6H₂O, 2,4-[6-(4-carboxyphenyl)pyrazin-2-yl]benzoic acid (H₂L) and two auxiliary N-donor linkers, 1,10-phenanthroline (phen) and 1,4-bis(1H-imidazol-1-yl)benzene (dib) to assist in the self-assembly process. The resulting compounds were identified as [Mn(L)(phen)]_n (1) and {[Mn(L)(H₂O)]·0.5dib}_n (2). 1 displays a one-dimensional (1D) structure, which is further assembled to form a 2D structure through weak interactions between adjacent L²⁻ ligands. In contrast, 2 shows a 2D network, which can further form a 3D supramolecular network via packing interactions between the 2D networks. Focusing on the structure around manganese(II) ions, both 1 and 2 have bis(μ-carboxylate-κO:κO′)dimanganese(II) structures. The cryomagnetic behavior for 1 and 2 was complicated, suggesting the temperature-induced structural change due to the flexibility of the Mn(II) compounds. The unique magnetic behaviors exhibited by the two complexes also provide a new perspective for the subsequent study of magnetic materials.