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Ferromagnetic Coupling in the Three-Dimensional Malonato-Bridged Gadolinium(III) Complex [Gd2(mal)3(H2O)6] (H2mal = Malonic Acid)

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posted on 05.08.2003, 00:00 by María Hernández-Molina, Catalina Ruiz-Pérez, Trinidad López, Francesc Lloret, Miguel Julve
The novel gadolinium(III) complex of formula [Gd2(mal)3(H2O)6] (1) (H2mal = 1,3-propanedioic acid) has been prepared and characterized by X-ray diffraction analysis. Crystal data for 1:  monoclinic, space group I2/a, a = 11.1064(10) Å, b = 12.2524(10) Å, c = 13.6098(2) Å, β = 92.925(10)°, U = 1849.5(3) Å3, Z = 4. Compound 1 is a three-dimensional network made up of malonate-bridged gadolinium(III) ions where the malonate exhibits two bridging modes, η5-bidentate + unidentate and η33 + bis(unidentate). The gadolinium atom is nine-coordinate with three water molecules and six malonate oxygen atoms from three malonate ligands forming a distorted monocapped square antiprism. The shortest metal−metal separations are 4.2763(3) Å [through the oxo-carboxylate bridge] and 6.541(3) Å [through the carboxylate in the antisyn coordination mode]. The value of the angle at the oxo-carboxylate atom is 116.8(2)°. Variable-temperature magnetic susceptibility measurements reveal the occurrence of a significant ferromagnetic interaction through the oxo-carboxylate pathway (J = +0.048(1) cm-1, H = −JSGd(1)·SGd(1a)).