Dynamic magnetic materials based on the cationic coordination polymer [Cu(btix)_2]_n ~(2n+) [btix = 1,4-bis(triazol-1- ylmethyl)benzene]: Tuning the structural and magnetic properties through anion exchange

摘要

A three-dimensional coordination polymer, [Cu(btix)_2(BF _4)_2])n [btix = 1,4-bis(triazol-1-ylmethyl) benzene], with antiferromagnetic interactions occurring via the organic ligand, has been prepared and characterized. It has been shown to permit the exchange of anionic species in the crystalline network with modification of the magnetic properties. Coordinated BF_4 ~- can be reversibly exchanged by different anions with (NO_3 ~- and Cl~-) or without (PF_6 ~- and ClO_4 ~-) dynamic response of the organic ligand, which acts as the only linker between the metal centers. Interestingly, an irreversible exchange occurs with N_3 ~- anions to generate a new coordination polymer, [Cu(btix)(N _3)_2]_n, whose structure has been determined ab initio by powder X-ray diffraction, revealing a totally different connectivity between the Cu~(II) centers. These structural transformations are accompanied by a change of the magnetic properties, which have been detected by electron paramagnetic resonance and magnetic susceptibility measurements.