Tuning magnetic properties by crystal engineering in a family of coordination polymers based on Ni(II) sulphates

A new family of hybrid organic-inorganic layered materials based on nickel sulfates was synthesized using a simple, solvent-free synthesis approach using 1,2-phenylenediamine (OPD), 1,3-phenylenediamine (MPD), and 1,4-phenylenediamine (PPD) as organic templates and ligands. Diamines act as structure-directing agents to obtain 1D [Ni(OPD)(2)SO4] (1), 2D [Ni(MPD)(2)SO4] (2) and 3D [Ni(PPD)SO4] (3) frameworks. The crystal structures of 1-3 were determined using data from X-ray powder diffraction (XRPD) measurements and represent I2/a, Cc, and Cmcm space groups, respectively. The compounds display different dimensionalities of the frameworks; however, the magnetic studies reveal transitions to 3D magnetic long-range ordered phases in all three cases below 23 K (1), 25 K (2) and 25 K (3). The observed ordering in all compounds is a consequence of significant interchain (1) and intralayer (2 and 3) interactions which lead to considerable spin-spin correlations, which are strong enough to couple the adjacent layers. In addition, in all three compounds, there is a competition between ferromagnetic and antiferromagnetic interactions in which the latter ones successively get stronger with the substitution of dipolar couplings by superexchange ones.