| Abstract
| - A new lanthanide citrate motif of general formula [Ln(Hcit)(H2O)2·H2O]n, where Ln = Gd (1) and Nd (2) and Hcit3-= C(OH)(COO-)(CH2COO-)2, has been synthesized hydrothermally from Ln2O3 and citric acid at 100 °C andcharacterized by elemental analysis, IR, TG-DTA, single-crystal X-ray diffraction, and magnetic measurements.The structures can be seen as “ladder chains” along the a axis, with dinuclear Ln2O2 units serving as “steps” andR−COO groups as “uprights”, which are connected by H bonds. The magnetic susceptibility between 2 and 300K and the magnetization at 2 K, as a function of magnetic field between 0 and 5 T, were measured for bothcompounds. By modeling the magnetic behavior of the Gd compound with a dinuclear Hamiltonian ℋS = gμB(SA+ SB)Bo − JoSASB (SA = SB = 7/2), a ferromagnetic exchange interaction Jo = 0.039 cm-1 was evaluated betweenGd ions situated at do = 4.321 Å in dinuclear units bridged by two symmetry-related tridentate carboxylate oxygens.The EPR spectrum of the Gd compound is discussed. The temperature dependence of the susceptibility of the Ndcompound is caused by the depopulation of the excited crystal-field levels when the temperature decreases. Themagnetic-field dependence of the magnetization of 2 is attributed to the ground-state Kramers' doublet populatedat 2 K. The g factor of this ground-state doublet is calculated from the data and compared with values for othercompounds reported in the literature.
- Two new one-dimensional coordination polymers of Gd(III) and Nd(III) with citrate ligands, [Ln(Hcit)(H2O)2·H2O]n, were synthesized by hydrothermal reactions and structurally characterized. The compounds contain isostructural chains built by Ln nodes bridged by carboxylate groups and connected by H bonds. A ferromagnetic exchange interaction Jo = 0.039 cm-1 between Gd(III) ions in dinuclear units was evaluated.
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