o-Phenylenedioxydiacetate complexes of Gd(III) and Ce(III): syntheses, crystal structures, and magnetic properties

{[Ln(2)(PDOA)(3)(H2O)(6)]center dot 2H(2)O}(n) (Ln = Gd, 1; Ln = Ce, 2; H(2)PDOA = o-phenylenedioxydiacetic acid) has been synthesized and characterized by chemical analyses, IR spectroscopy, and thermal analyses. Single-crystal X-ray structure analyses revealed that both 1 and 2 are polymeric and built up of a ladder-like arrangement of Ln(III) ions linked by short syn-anti carboxylate bridges and long bridges (legs of the ladder) formed by a second crystallographically independent PDOA. Ln(III) in both 1 and 2 is nine-coordinate with an O-9 donor set formed by one chelating/bridging and one bridging PDOA, and an additional three waters. In the asymmetric unit, there is one crystallographically independent water of crystallization, which is involved in a rich system of hydrogen bonds of the O-H center dot center dot center dot O type. The identities of the bulk and single crystal phases were corroborated by powder X-ray diffraction. Variable temperature (2-300 K) magnetic studies indicate the presence of only weak antiferromagnetic interactions between pairs of paramagnetic Ln(III) ions with J/hc = -0.004 and -0.13 cm(-1), for 1 and 2.