Magnetic study of a one-dimensional Mn(II) coordination polymer dealing with π–π stacking

A new one-dimensional chain manganese(II) coordination polymer, {[Mn(μ-Dpd)(Q)2(H2O)2]2(ClO4)}n (Dpd = 2,5-dimethylpyrazine-1,4-dioxide; Q = 8-hydroxylquinoline N-oxide), was synthesized with 2,5-dimethylpyrazine-1,4-dioxide as bridge ligand and 8-hydroxylquinoline N-oxide as terminal ligand, and its crystal structure determined by X-ray crystallography. The structure analysis indicates that there are two pathways for magnetic interactions: one is through bridge ligand 2,5-dimethylpyrazine-1,4-dioxide, and another is by π–π stacking of adjacent quinoline rings. The theoretical calculations reveal that there exist a anti-ferromagnetic interaction from spin delocalization and a ferromagnetic interaction from spin polarization for 2,5-dimethylpyrazine-1,4-dioxide bridge pathway, but the anti-ferromagnetic interaction is stronger than the ferromagnetic interaction, leading to an anti-ferromagnetic interaction with J = −2.53 cm−1; whereas for the π–π stacking pathway it resulted in a ferromagnetic interaction with J = 0.013 cm−1. The experimental fitting on the data of the variable temperature magnetic susceptibilities gave the magnetic interaction constant J = 0.07 cm−1, which is similar with the results of the theoretical calculations.