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(mu-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-dimethylprazine-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 pi-pi 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 pi-pi 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. (c) 2008 Elsevier B.V. All rights reserved.