Polymorphism of isotypic series of homoleptic 1,2,3-triazolate MOFs [Ln(Tz*)₃] containing the heavy lanthanides Gd–Lu: from open to dense frameworks of varying dimensionality

Abstract

Homoleptic MOF structures of the formulas 2 1 [Ln(Tz*) 3 ] and 31 [Ln(Tz*) 3 ], (Tz*) À ¼ 1,2,3-triazolate anion, C 2 H 2 N 3 À , Ln ¼ Gd-Lu, were obtained by the reaction of the lanthanide metals with the aromatic heterocyclic amine 1H-1,2,3-triazole. The isotypic series of compounds are real polymorphs as they have identical constitution. The 2-dimensional MOF is formed at lower temperatures whereas formation of the 3-dimensional MOF requires higher temperatures, in some cases solvothermal reaction conditions. We therefore address them as low-temperature a-form and high-temperature b-form. The thermodynamically stable b-form exhibits high thermal stabilities regarding compounds that contain three neighboring nitrogen atoms in one organic ring, ranging up to 380 C. Transition from a-to b-form is accompanied by transformation from open to dense frameworks as only the a-form contains structural voids. This goes along with both an increase of dimensionality of the linkage from 2D to 3D and an increase of the density of the structures. The a-form adopts the AlCl 3 structure, the b-form can be identified with a (10,3)-b net. Although no single crystals could be obtained for b-3 1 [Ln(Tz*) 3 ], structure solution and reasonable refinement were successful from Xray powder data. The crystal structure of a-2 1 [Ln(Tz*) 3 ] was previously solved from single crystal data.

Utilising Metal Melts of Low‐Melting Metals as a Novel Approach for MOF Synthesis: The 3D‐Imidazolate 3∞[Ga2(Im)6ImH] from Gallium and Imidazole

“…They do not derive from 3 ∞ [Ga 2 (Im) 6 ImH] itself (see Figure 1, bottom), as also the powder pattern of the product of signal (2) "[Ga(Im) 3 ]" differs strongly from the pattern of 3 ∞ [Ga 2 (Im) 6 ImH], whereas the powder patterns of "[Ga(Im) 3 ]" from the glass tube oven experiment and the DTA/TG experiment show the same pattern. Unfortunately, crystallinity of "[Ga(Im) 3 ]" is too low allow a successful structure resolution from X-ray powder techniques, which prove successful only for a certain crystallinity and at best high symmetry [18].…”

Solvothermal and Ultrasonic Preparation of Two Unique Cluster-Based Lu and Y Coordination Materials: Metal–Organic Framework-Based Ratiometric Fluorescent Biosensor for an Ornidazole and Ronidazole and Sensing Platform for a Biomarker of Amoeba Liver Abscess

“…Furthermore, it should be noted that work on the preparation and application of lanthanide Lu-based and Y-based MOFs is still scarcely reported. − However, Lu-based MOF and Y-based MOF show great potential applications. For example, previously Rybak et al have reported the interesting polymorphism of an isotypic series of heavy lanthanides Gd–Lu based MOFs, which can be tuned from open to dense frameworks of varying dimensionality …”

“…For example, previously Rybak et al have reported the interesting polymorphism of an isotypic series of heavy lanthanides Gd−Lu based MOFs, which can be tuned from open to dense frameworks of varying dimensionality. 16 Although these lanthanide MOFs have highly stable luminescent efficiency, single chromophores still may be easily influenced by other external interference factors such as optical occlusion, atmosphere, excitation power fluctuation, and pressure. However, these ratiometric fluorescent sensors 17−19 can be constructed based on the emission intensity ratio of two independent fluorescence signal bands, which can circumvent many external complications, and thus these ratiometric fluorescent sensors are gathering more attention.…”

Temperature-Dependent Supramolecular Isomerism of Lutetium-Aminoterephthalate Metal–Organic Frameworks: Synthesis, Crystallography, and Physical Properties

“…In particular, the use of temperature enables researchers to take advantage of entropic differences between alternative products . As illustrated by several studies, − different polymorphic phases of MOFs can be obtained from a single reaction mixture held at different temperatures. Among them, the experimental and theoretical studies carried out on a series of polymorphic La-based MOFs reveal that the kinetic metastable and thermodynamic phases could be isolated as pure products over certain temperature ranges .…”