A Series of 2D and 3D Novel Lanthanide Complexes Constructed from Squarate C4O42–: Syntheses, Structures, Magnetic Properties, and Near-infrared Emission Properties

Abstract

The solvothermal combination of trivalent lanthanide metal precursors with a squarate ligand (H2C4O4, 3,4-dihydroxy-3-cyclobutene-1,2-dione) has afforded the preparation of a family of eight new coordination polymers, [Ln2(C4O4)3(H2O)4] (Ln = La–Nd, Ho) (1–5), [Ln2(C4O4)3(H2O)8] (Ln = Er, Dy) (6, 7), and Tb2(C4O4)2(C2O4)(H2O)4 (8). Structural analysis reveals that the squarate ligand displays versatile coordination modes to generate novel 2D and 3D frameworks. Three new coordination modes, a bidentate/monodentate μ3 and two bidentate/monodentate μ4 coordination modes, are first reported. In addition, the variable-temperature magnetic properties of the Pr, Nd, Ho, Dy, and Tb complexes, the solid-state near-infrared luminescence spectra of the Pr, Nd, Ho, and Er complexes, and their thermogravimetric analyses are discussed.

Trivalent f-Element Squarates, Squarate-Oxalates, and Cationic Materials, and the Determination of the Nine-Coordinate Ionic Radius of Cf(III)

“…Cyclic oxocarbon acids, such as squaric acid (H 2 C 4 O 4 , 3,4-dihydroxycyclobut-3-ene-1,2-dione), are of interest because of their cyclic structures, aromatic nature, wide-ranging chemical and physical properties leading to a variety of materials applications, , and varying coordination modes in coordination and structural studies. − These varying coordination modes (variable denticities and bridging abilities) are attractive for the potential to produce novel extended networks. Squarate was chosen as a ligand of interest here because of its unique coordination modes and the fact that its aromatic/delocalized bonding makes the oxo donors of the ligand “softer” (under the Pearson definition) than would otherwise be expected.…”

Polymeric Terbium(III) Squarate Hydrate as a Luminescent Magnet

“…In the previous work [11,12,27,28], several pseudo-polymorphs are separated depending on the bridging mode of sq and the number of solvent (water) molecules ligating to metal ions and incorporated as a guest: [{Ln2(sq)3(H2O)4}n], [{Ln2(sq)3(H2O)11}n] . (H2O)2, [Ln(Hsq)(sq)(H2O)6], [Ln(Hsq)(sq)(H2O)6] .…”

“…Since then, the space groups reported were controversial; P21/c was chosen for Gd-sq [14] with one sq missing, presumably owing to disordered weak electron density. For Dy-and Er-sq [28], P21/c was assumed, but a severe overlap of the atomic coordinates remained. We encountered a similar centrosymmetry/non-centrosymmetry problem, and finally concluded that the most plausible space group is Pc based on the rational crystal structure (Figure 1b,c).…”

Synthesis, Structural Characterization and Ligand-Enhanced Photo-Induced Color-Changing Behavior of Two Hydrogen-Bonded Ho(III)-Squarate Supramolecular Compounds

“…Compared 1 , 2 and the other Ho(III)-squarate polymeric framework, [Ho 2 (C 4 O 4 ) 3 (H 2 O) 4 ] n ( 3 ), synthesized under solvothermal condition reported in the previous literature [66]. The Ho(III) ions in 1 an 2 are both eight-coordinate, but, in 3 , is nine coordinate with a tricapped trigonal prismatic coordination environment.…”

“…The squarate, C 4 O 4 2− , has been widely used as a polyfunctional ligand, including (1) acts as a bridging ligand with various coordination modes (μ 2 to μ 6 bridges shown in Scheme 1) to build up many coordination polymers with novel extended networks, including 1D chain, 2D layer, 3D cube- and cage-like frameworks and so forth and (2) behaviors as hydrogen bond donor, acceptor or π−π constructor for the assembly of extended supramolecular architecture [30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63]. In the previous investigation, several 2D and 3D LnMOFs constructed via the bridges of lanthanide and squarate ligand with various coordination modes have been synthesized under hydrothermal or solvothermal conditions [64,65,66,67,68,69,70]. Their thermal behavior, magnetic property and photo-luminescence spectra of 2D and 3D LnMOFs have also been studied.…”