Ferromagnetic coupling in the three-dimensional malonato-bridged gadolinium(III) complex [Gd2(mal)3(H2O)6] (H2mal = malonic acid)

The novel gadolinium(Ill) complex of formula [Gd-2(mal)(3)(H2O)(6)] (1) (H(2)mal = 1,3-propanedioic acid) has been prepared and characterized by X-ray diffraction analysis. Crystal data for 1: monoclinic, space group 12/a, a = 11.1064(10) Angstrom, b = 12.2524(10) Angstrom, c = 13.6098(2) Angstrom, beta = 92.925(10)degrees, U = 1849.5(3) Angstrom(3), Z = 4. Compound 1 is a three-dimensional network made up of malonate-bridged gadolinium(Ill) ions where the malonate exhibits two bridging modes, eta(5)-bidentate + unidentate and eta(3):eta(3) + 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) Angstrom [through the oxo-carboxylate, bridge] and 6.541(3) Angstrom [through the carboxylate in the anti-syn coordination mode]. The value of the angle at the oxo-carboxylate atom is 116.8(2)degrees. Variable-temperature magnetic susceptibility measurements reveal the occurrence of a significant ferromagnetic interaction through the oxo-carboxylate pathway (J = +0.048(l) cm(-1), H = -JS(Gd(1)).S-Gd(1a)).