A 3D Iron(II)-Based MOF with Squashed Cuboctahedral Nanoscopic Cages Showing Spin-Canted Long-Range Antiferromagnetic Ordering

The
reaction of dilithium squarate with Fe­(II) perchlorate led
to the formation of a new Fe­(II)-based 3D MOF, [Fe3(OH)3(C4O4)­(C4O4)0.5]n (1), with homoleptic
squashed cuboctahedral cages. Complex 1 crystallizes
in the monoclinic C2/c space group.
Fe­(II) centers in the complex are octahedrally coordinated by four
squarate dianions in axial and equatorial positions and two hydroxyl
groups in the remaining equatorial positions. The interesting structural
feature of 1 is that the three-dimensional framework
is an infinite extension of nanoscopic cuboctahedral cages. The framework
also contains two types of voids; the larger hydrophobic ones are
surrounded by aromatic squarate ligands, while the smaller ones are
hydrophilic with hydroxyl groups on the surface connected by bifurcated
hydrogen bonding interaction. A variable temperature magnetic study
shows spin-canted long-range antiferromagnetic ordering in the low
temperature regime.