Three-dimensional metal phosphonodicarboxylates with GIS-zeolite topology: syntheses, structures and magnetic studies

Abstract

Compounds [M₂(4-pi)(H₂O)₄]·1.5H₂O [M(II) = Mn(1), Co(2), Ni(3)] and a heterometallic analogue [Co_1.14Ni_0.86(4-pi)(H₂O)₄]·1.5H₂O (4) have been synthesized utilizing a rigid 4-phosphonoisophthalic acid (4-piH₄). Compounds 1–4 are isostructural, confirmed by their powder XRD measurements. Single crystal structural determinations of 1 and 2 reveal that these compounds display a novel pillared layered open framework structure with zeolite gismondine (GIS) topology. Within the layer, edge-sharing {MO₆} octahedra are found, which are connected by carboxylate and phosphonate groups along the c- and b-axis, respectively. Dominant antiferromagnetic interactions are propagated between the magnetic centers in 1, 2 and 4. While in 3, ferromagnetic exchange couplings are observed.