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Rational Design of 2D Magnetic Metal−Organic Coordination Polymers Assembled from Oxalato and Dipyridyl Spacers

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posted on 02.08.2006, 00:00 by Urko García-Couceiro, Oscar Castillo, Antonio Luque, Juan P. García-Terán, Garikoitz Beobide, Pascual Román
The use of 1,2-bis(4-pyridyl)ethane (bpa) and 1,2-bis(4-pyridyl)ethylene (bpe) as spacers has allowed us the rational design of new two-dimensional compounds having molecular formulas [M(μ-ox)(μ-bpa)]n (M(II) = Zn (1), Ni (2), Mn (3), Fe (4), or Cu (5); ox = oxalate dianion) and [M(μ-ox)(μ-bpe)]n (M(II) = Zn (6), Ni (7), Co (8), Fe (9), or Cu (10)). These compounds have been synthesized using diffusion and hydrothermal methods, and they have been characterized by FT-IR spectroscopy, thermal analysis, and variable-temperature magnetic measurements. The X-ray structural analysis reveals that each metal atom is six-coordinated to four oxygen atoms belonging to two bridging oxalato ligands and two nitrogen atoms of two bidentate dipyridyl molecules to afford the expected 2D rectangular grid-type networks in which infinite [M(μ-ox)]n chains are cross-linked by the organic spacers. Each layer contains rectangles with dimensions of ca. 5 Å × 14 Å, the edges being defined by the oxalato and dipyridyl ligands. These rectangular cavities remain empty. Variable-temperature magnetic susceptibility data show an overall antiferromagnetic behavior for all compounds except for Cu(II) polymers (5 and 10), which exhibit ferromagnetic interactions through the oxalato bridge in good accordance with their structural parameters.

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