Three Mn(ii) coordination polymers with a bispyridyl-based quinolinate ligand: the anion-controlled tunable structural and magnetic properties

Abstract

Three new Mn(II) coordination polymers, namely [Mn₃L₆·2H₂O] (1), [MnL₂] (2), and [MnL₂·2H₂O] (3), were prepared by solvothermal reactions of Mn(II) salts with a bispyridyl-based quinolinate ligand. All complexes were characterized by elemental analysis, IR spectra, powder and single-crystal X-ray crystallography. Single crystal X-ray studies show that these coordination polymers exhibit a structural diversification due to the different counteranions (OAc⁻, Cl⁻, and NO₃⁻). Complex 1 has a 2D supramolecular structure with a cyclic tetramer Mn₃L₆ secondary building unit. Complex 2 possesses a rhombohedral grid network containing a type of meso-helical chain (P + M) constructed via the metal–ligand coordination interaction. Complex 3 features a 3D non-porous structure based on the arrangement of 2D grids. Magnetic susceptibility measurements indicate that the three Mn(II) polymers 1–3 show disparate magnetic properties due to their different supramolecular structures.