Diverse Lanthanide Coordination Polymers with 3,3′-Dimethylcyclopropane-1,2-dicarboxylate Ligand: Synthesis, Crystal Structure, and Properties

In an attempt
to investigate the influence of many variables on the synthesis of
lanthanide coordination polymers (Ln-CPs) assembled from the ligand
3,3-dimethylcyclopropane-1,2-dicarboxylic acid, three different Ln-CPs
with formulae [La9(μ4-dcd)12(μ3-O)2(H)]n (1), [Gd4(μ4-dcd)6(H2O)]n (2),
and [Gd2(μ3-OH)2(μ3-dcd)­(μ2-ac)2(H2O)]n (3) (dcd = 3,3-dimethylcyclopropane-1,2-dicarboxylate,
ac = acetate) have been hydrothermally synthesized and structurally
characterized by elemental analysis, IR spectrum, thermal analysis,
powder X-ray diffraction, and single X-ray diffraction techniques. 1 represents the first report of the three-dimensional (3D)
Ln-CPs based on nonanuclear lanthanide clusters, although it shows
extremely low gas uptakes. 2 exhibits one of the previously
reported 3D lanthanide wheel cluster-like frameworks. 3 characterizes a novel one-dimensional ladder-like chain [Gd4(OH)4]n decorated with
mixed ligand ribbons. Variable-temperature magnetic susceptibility
measurement reveals that the shortest Gd···Gd distance
in 3 induces the antiferromagnetic interactions between
adjacent Gd3+ cations within the hydroxyl-bridged binuclear
unit. Remarkably, magnetic investigation for 2 indicates
a unique metamagnetic transition from the antiferromagnet to ferromagnet.
Furthermore, magnetic studies for 2 also exhibit the
presence of significant magnetocaloric effect with a large magnetic
entropy change.