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

Abstract

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)₂SO₄] (1), 2D [Ni(MPD)₂SO₄] (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.