Two new cadmium(II) coordination polymers based on imidazole-containing ligands: synthesis, structural characterization and fluorescence properties

The judicious selection of suitable ligands is vitally important in the construction of novel metal-organic frameworks (MOFs) with fascinating structures and interesting properties. Recently, imidazole-containing multidentate ligands have received much attention. Two new Cd^II coordination frameworks, namely, poly[tris{μ-1,4-bis[(1H-imidazol-1-yl)methyl]benzene-κ²N³:N^3'}tetrakis(nitrato-κ²O,O')dicadmium], [Cd₂(NO₃)₄(C₁₄H₁₄N₄)₃]_n, (I), and poly[[bis{μ₃-1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene-κ³N³:N^3':N^3''}cadmium] hexafluorosilicate], {[Cd(C₁₈H₁₈N₆)₂](SiF₆)}_n, (II), have been synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. In polymer (I), the 1,4-bis[(1H-imidazol-1-yl)methyl]benzene ligand bridges Cd²⁺ ions with a distorted seven-coordinated pentagonal bipyramidal geometry, forming a one-dimensional ladder chain, and the nitrate anions coordinate to the Cd²⁺ ions in a terminal bidentate fashion. In the crystal, adjacent chains are further connected by C-H...O hydrogen bonds to generate a two-dimensional (2D) supramolecular structure. Polymer (II) exhibits a 2D layered structure in which 1,3,5-tris[(1H-imidazol-1-yl)methyl] benzene ligands join Cd²⁺ centres having a six-coordinated octahedral structure. The layers are connected by hexafluorosilicate anions via C-H...F hydrogen-bond interactions, giving rise to a three-dimensional supramolecular network structure in the solid state. In addition, powder X-ray diffraction (PXRD) patterns were recorded, thermogravimetric analyses (TGA) carried out and fluorescence properties investigated.

Hydrothermal synthesis, crystal structure and properties of a two-dimensional uranyl coordination polymer based on a flexible zwitterionic ligand

The interaction between the uranyl cation, (UO₂)²⁺, and organic species is of interest due to the potential applications of the resulting compounds with regard to nuclear waste disposal and nuclear fuel reprocessing. The hydrothermal reaction of various uranyl compounds with flexible zwitterionic 1,1'-[1,4-phenylenebis(methylene)]bis(pyridin-1-ium-4-carboxylate) dihydrochloride (Bpmb·2HCl) in deionized water containing drops of H₂SO₄ resulted in the formation of a novel two-dimensional uranyl coordination polymer, namely poly[tetraoxido{μ₂-1,1'-[1,4-phenylenebis(methylene)]bis(pyridin-1-ium-4-carboxylate)}di-μ₃-sulfato-diuranium(VI)], [(UO₂)₂(SO₄)₂(C₂₀H₁₆N₂O₄)]_n, (1). Single-crystal X-ray diffraction reveals that this coordination polymer exhibits a layered arrangement and the (UO₂)²⁺ centre is coordinated by five equatorial O atoms. The structure was further characterized by FT-IR spectroscopy, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA). The polymer shows high thermal stability up to 696 K. Furthermore, the photoluminescence properties of (1) has also been studied, showing it to exhibit a typical uranyl fluorescence.

Extremely stable europium-organic framework for luminescent sensing of Cr2O72− and Fe3+ in aqueous systems

A novel Eu-MOF which is extremely stable in an aqueous system over a wide pH range is reported as a dual functional Cr₂O₇²⁻ and Fe³⁺ sensor in aqueous environments.

Multifunctional Material with Efficient Optoelectronic Integrated Molecular Switches Based on a Flexible Thin Film/Crystal

Switchable materials, due to their potential applications in the fields of sensors, photonic devices, digital processing, etc., have been developed drastically. However, they still face great challenges in effectively inducing multiple molecular switching. Herein organic-inorganic hybrid compounds, an emerging class of hydrosoluble optoelectronic-active materials, welcome a new member with smart unique optical/electrical (fluorescence/dielectric) dual switches (switching ON/OFF), that is, [C₅H₁₃NBr][Cd₃Br₇] (1) in the form of both a bulk crystal and an ultraflexible monodirectional thin film, which simultaneously exhibits fast dielectric/fluorescent dual switching triggered by an optical/thermal/electric signal with a high signal-to-noise ratio of 35 (the highest one in the known optical/dielectric dual molecular switches). Additionally, the exceptional stability/fatigue resistance as well as the fantastic extensibility/compactness of thin films (more than 10000 times folding over 90°), makes 1 an ideal candidate for single-molecule intelligent wearable devices and seamlessly integrated optoelectronic multiswitchable devices. This opens up a new route toward advanced light/electric high-performance switches/memories based on organic-inorganic hybrid compounds.

Controllable assembly of Cu(ii) coordination compounds based on a flexible zwitterionic benzimidazole–dicarboxylate ligand: synthesis, structural diversity, reversible SCSC transformation and magnetic properties

The reversible SCSC transformation of a paddle-wheel cluster to a 1D linear polymer could be accomplished.

The structural diversity and properties of nine new viologen based zwitterionic metal–organic frameworks

A viologen based ligand has been explored as a functional building block to synthesize a series of nine new zwitterionic metal–organic frameworks with this contribution reporting on their structural, thermal and photochromic properties.

Designed synthesis of a series of zwitterion–polyoxometalate hybrid materials for selective scavenging and photolysis of dyes

An effective strategy to immobilize both zwitterion and POM moieties into porous hybrid materials was developed. These materials demonstrate remarkable efficiency for selective scavenging and photolysis of cationic dyes from polluted water.

Syntheses, characterization and properties of nine novel Zn(ii) coordination polymers based on 4,4′-(phenylazanediyl)dibenzoic acid and various N-donor ligands

An 2D sheet consists of two kind of 1D helical chains. The corresponding helical chains in adjoining layers exhibit the opposite handedness.

Coordination polymers of a multipyridyl and pyrazolyl ligand with conformational flexibility: syntheses, structures and luminescence

Eight novel coordination polymers were obtained by the coordination of a multipyridyl and pyrazolyl ligand, which shows rich conformational changes.

Assembly of a series of d10 coordination polymers of pamoic acid through a mixed-ligand synthetic strategy: syntheses, structures and fluorescence properties

Eight fluorescent coordination compounds were obtained based on H₂PA and N-donor ligands through a mixed-ligand synthetic strategy.