A series of lanthanide-organic frameworks constructed by 2-methyl imidazole dicarboxylate and oxalate: synthesis, structures, and properties

Abstract

Five lanthanide(III) coordination polymers with 2-methyl-1H-imidazole-4,5-dicarboxylic acid (H 3 MIDC) and ammonium oxalate,have been prepared and structurally characterized. Single-crystal X-ray diffraction analyses reveal that 1 and 2 are isostructural, as are 3, 4, and 5. Each exhibits a 3-D open framework, which is built by a regular 2-D grid connected by HMIDC 2À and Ln(III). The luminescence and thermal properties of these complexes have been investigated as well.

High and Tunable Proton Conduction in Six 3D-Substituted Imidazole Dicarboxylate-Based Lanthanide–Organic Frameworks

“…Syntheses of Ln-MOFs. 1 was synthesized by the reference method, 52 with a slight improvement: a mixture of Gd(NO 3 ) 3 Because the crystal structures of Ln-MOFs 1−6 have been described in detail 37,52,53 and they are isostructural compounds, we mainly take MOF 1 as the representative in this paper to briefly describe their crystal structural characteristics that are conducive to proton conduction. For MOF 1, its asymmetric unit contains two crystallographically independent Gd III atoms, two HMIDC 2− ions, one oxalate ion, three coordinated H 2 O units, and four free H 2 O units (Figure 1a).…”

“…53,56 As is well-known to all, imidazole-4,5-dicarboxylic acid and its 2-position substituted derivatives have been utilized to construct novel MOFs with novel structures. 57−59 Consequently, several related Ln-MOFs were described previously, but most of them are concerning photoluminescence and magnetic properties, 37,52,53 and the research on proton conduction is very limited. Indeed, only two threedimensional (3D) Tb/Eu-MOFs built by 2-phenyl-1Himidazole-4,5-dicarboxylic acid exhibiting high σ values around 10 −4 under 100 °C-98% RH have been reported by our team.…”

“…Note that the selection of organic ligands is crucial to the preparation of functional MOFs. Various organic ligands such as Schiff base and pyridine carboxylate compounds are broadly adopted in the synthesis of Ln-MOFs. − For oxygen-containing organic ligands, the carboxylic acid ligands are an important class of functional ligands because carboxylic acid ligands have diverse coordination modes when they are coordinated with metal centers. − The Ln ions have a strong appetency for O; hence, the carboxylate compounds were widely used as bridges or linkers in the frameworks of Ln-MOFs. , As is well-known to all, imidazole-4,5-dicarboxylic acid and its 2-position substituted derivatives have been utilized to construct novel MOFs with novel structures. − Consequently, several related Ln-MOFs were described previously, but most of them are concerning photoluminescence and magnetic properties, ,, and the research on proton conduction is very limited. Indeed, only two three-dimensional (3D) Tb/Eu-MOFs built by 2-phenyl-1 H -imidazole-4,5-dicarboxylic acid exhibiting high σ values around 10 –4 under 100 °C-98% RH have been reported by our team .…”

“…The isostructural Ln-MOFs 1–6 feature unique 3D structures and abundant H-bonding interactions between imidazole-N atoms and coordinated and free H 2 O molecules. Note that although MOFs 1–6 have been synthesized as early as 2012, ,, the exploration of proton conduction has not been undertaken. AC impedance studies confirmed that they demonstrated prominently high σ values varying from 10 –4 to 10 –3 S·cm –1 (2.01 × 10 –3 , 1.40 × 10 –3 , 9.31 × 10 –4 , 2.25 × 10 –4 , 1.11 × 10 –4 , and 0.96 × 10 –4 S·cm –1 for 1–6 , respectively).…”

Synthesis, structure, and magnetism of a ytterbium coordination polymer with 5-sulfonyl-1,2,4-benzenetricarboxylate and oxalate

“…Combination of the characteristics of organic and inorganic components offers an opportunity to incorporate useful properties within a single composite, providing access to multifunctional materials. Lanthanides attract attention for unique physical properties arising from 4f electrons [6][7][8][9]. High coordination number and flexible coordination geometry of lanthanide ions make it difficult to control preparation of lanthanide compounds.…”