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Two-Dimensional 3d–4f Heterometallic Coordination Polymers: Syntheses, Crystal Structures, and Magnetic Properties of Six New Co(II)–Ln(III) Compounds
journal contribution
posted on 2014-06-16, 00:00 authored by Pau Díaz-Gallifa, Oscar Fabelo, Jorge Pasán, Laura Cañadillas-Delgado, Francesc Lloret, Miguel Julve, Catalina Ruiz-PérezSix new heterometallic cobalt(II)-lanthanide(III)
complexes of formulas [Ln(bta)(H2O)2]2[Co(H2O)6]·10H2O [Ln = Nd(III)
(1) and Eu(III) (2)] and [Ln2Co(bta)2(H2O)8]n·6nH2O [Ln = Eu(III) (3), Sm(III) (4), Gd(III) (5), and
Tb(III) (6)] (H4bta = 1,2,4,5-benzenetretracaboxylic
acid) have been synthesized and characterized via single-crystal X-ray
diffraction. 1 and 2 are isostructural compounds
with a structure composed of anionic layers of [Ln(bta)(H2O)2]nn– sandwiching mononuclear [Co(H2O)6]2+ cations plus crystallization water molecules, which
are interlinked by electrostatic forces and hydrogen bonds, leading
to a supramolecular three-dimensional network. 3–6 are also isostructural compounds, and their structure consists
of neutral layers of formula [Ln2Co(bta)2(H2O)8]n and crystallization
water molecules, which are connected through hydrogen bonds to afford
a supramolecular three-dimensional network. Heterometallic chains
formed by the regular alternation of two nine-coordinate lanthanide(III)
polyhedra [Ln(III)O9] and one compressed cobalt(II) octahedron
[Co(II)O6] along the crystallographic c-axis are cross-linked by bta ligands within each layer of 3–6. Magnetic susceptibility measurements
on polycrystalline samples for 3–6 have been carried out in the temperature range of 2.0–300
K. The magnetic behavior of these types of Ln(III)–Co(II) complexes,
which have been modeled by using matrix dagonalization techniques,
reveals the lack of magnetic coupling for 3 and 4, and the occurrence of weak antiferromagnetic interactions
within the Gd(III)−Gd(III) (5) and Tb(III)−Tb(III)
(6) dinuclear units through the exchange pathway provided
by the double oxo(carboxylate) and double syn–syn carboxylate
bridges.