Thiacalix[4]arene-supported molecular clusters for catalytic applications

Designing External Pores of Aluminum Oxo Polyhedrons for Efficient Iodine Capture

Although metal-organic polyhedra (MOPs) expansion has been studied to date, it is still a rare occurrence for their porous intermolecular assembly for iodine capture. The major limitation is the lack of programmable and controllable methods for effectively constructing and utilizing the exterior cavities. Herein, the goal of programmable porous intermolecular assembly is realized in the first family of aluminum oxo polyhedrons (AlOPs) using ligands with directional H-bonding donor/acceptor pairs and auxiliary alcohols as structural regulation sites. The approach has the advantage of avoiding the use of expensive edge-directed ditopic and face-directed tritopic ligands in the general synthesis strategy of MOPs. Combining theoretical calculations and experiments, the intrinsic relationship is revealed between alcohol ligands and the growth mechanism of AlOPs. The maximum I2 uptake based on the mass gain during sorption corresponds to 2.35 g g-1, representing the highest reported I2 sorption by an MOP. In addition, it can be easily regenerated and maintained the iodine sorption capacity, revealing its further potential application. This method of constructing stable and programmable porous materials will provide a new way to solve problems such as radionuclide capture.

Utilizing magnetic xanthan gum nanocatalyst for the synthesis of acridindion derivatives via functionalized macrocycle Thiacalix[4]arene

An effective method for synthesizing acridinedione derivatives using a xanthan gum (XG), Thiacalix[4]arene (TC4A), and iron oxide nanoparticles (IONP) have been employed to construct a stable composition, which is named Thiacalix[4]arene-Xanthan Gum@ Iron Oxide Nanoparticles (TC4A-XG@IONP). The process used to fabricate this nanocatalyst includes the in-situ magnetization of XG, its amine modification by APTES to get NH2-XG@IONP hydrogel, the synthesis of TC4A, its functionalization with epichlorohydrine, and eventually its covalent attachment onto the NH2-XG@IONP hydrogel. The structure of the TC4A-XG@IONP was characterized by different analytical methods including Fourier-transform infrared spectroscopy, X-Ray diffraction analysis (XRD), Energy Dispersive X-Ray, Thermal Gravimetry analysis, Brunauer-Emmett-Teller, Field Emission Scanning Electron Microscope and Vibration Sample Magnetomete. With magnetic saturation of 9.10 emu g-1 and ~ 73% char yields, the TC4As-XG@IONP catalytic system demonstrated superparamagnetic property and high thermal stability. The magnetic properties of the TC4A-XG@IONP nanocatalyst system imparted by IONP enable it to be conveniently isolated from the reaction mixture by using an external magnet. In the XRD pattern of the TC4As-XG@IONP nanocatalyst, characteristic peaks were observed. This nanocatalyst is used as an eco-friendly, heterogeneous, and green magnetic catalyst in the synthesis of acridinedione derivatives through the one-pot pseudo-four component reaction of dimedone, various aromatic aldehydes, and ammonium acetate or aniline/substituted aniline. A combination of 10 mg of catalyst (TC4A-XG@IONP), 2 mmol of dimedone, and 1 mmol of aldehyde at 80 °C in a ethanol at 25 mL round bottom flask, the greatest output of acridinedione was 92% in 20 min.This can be attributed to using TC4A-XG@IONP catalyst with several merits as follows: high porosity (pore volume 0.038 cm3 g-1 and Pore size 9.309 nm), large surface area (17.306 m2 g-1), three dimensional structures, and many catalytic sites to active the reactants. Additionally, the presented catalyst could be reused at least four times (92-71%) with little activity loss, suggesting its excellent stability in this multicomponent reaction. Nanocatalysts based on natural biopolymers in combination with magnetic nanoparticles and macrocycles may open up new horizons for researchers in the field.

Recent advances in porous molecular cages for photocatalytic organic conversions

Photocatalytic organic conversion is considered an efficient, environmentally friendly, and energy-saving strategy for organic synthesis. In recent decades, the molecular cage has emerged as a creative functional material with broad applications in host-guest recognition, drug delivery, catalysis, intelligent materials and other fields. Based on the unique properties of porous molecular cage materials, they provide an ideal platform for leveraging pre-structuring in catalytic reactions and show great potential in various photocatalytic organic reactions. As a result, they have emerged as promising alternatives to conventional molecules or inorganic photocatalysts in redox processes. In this Review, the synthesis strategies based on coordination cages and organic cages, as well as their recent progress in photocatalytic organic conversion, are comprehensively summarized. Finally, we deliver the persistent challenges associated with porous molecular cage compounds that need to be overcome for further development in this field.

Atomically accurate structural tailoring of thiacalix[4]arene-protected copper(II)-based metallamacrocycles

Accurate manipulation of ligands at specific sites in robust clusters is attractive but difficult, especially for those ligands that coordinate in intricate binding patterns. By linking the shuttlecock-like {Cu₄(μ₄-Cl)TC4A} motif and the phenylphosphate (PhPO₃^2-) ligand, we elaborately design and synthesize two Cu(II)-thiacalix[4]arene metallamacrocycles (MMCs), namely Cu₁₂L₃ and Cu₁₆L₄, which have regular triangular and quadrilateral topologies, respectively. While keeping the core intact, the Cl^- and PhPO₃^2- in those two MMCs, which coordinated in a μ₄-bridging fashion, can be accurately substituted with salicylate ligands. Theoretical calculations have been carried out to reveal the effect of ligand tailoring on the electronic structure of clusters. Structural regulation can affect the catalytic activity of these clusters, which has been verified by using the clusters as catalysts for selective sulfide oxidation.

Sulfur-Bridged Co(II)-Thiacalix[4]arene Metal-Organic Framework as an Electrochemical Sensor for the Determination of Toxic Heavy Metals

A novel sulfur-bridged metal-organic framework (MOF) [Co(TIC4R-I)_0.25Cl₂]·3CH₃OH (Co-TIC4R-I) based on thiacalix[4]arene derivatives was successfully obtained using a solvothermal method. Remarkably, adjacent TIC4R-I ligands were linked via Co(II) cations to form a three-dimensional (3D) microporous architecture. Subsequently, Co-TIC4R-I was modified on a glassy carbon electrode (Co-TIC4R-I/GCE) to produce an electrochemical sensor for the detection of heavy-metal ions (HMIs), namely, Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺, in aqueous solutions. It was found that Co-TIC4R-I/GCE exhibited wide linear detection ranges of 0.10-17.00, 0.05-16.00, 0.05-10.00, and 0.80-15.00 μM for Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺, respectively, in addition to low limit of detection (LOD) values of 0.017, 0.008, 0.016, and 0.007 μM. Moreover, the fabricated sensor employed for the simultaneous detection of these metals has achieved LOD values of 0.0067, 0.0027, 0.0064, and 0.0037 μM for Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺, respectively. The sensor also exhibited satisfactory selectivity, reproducibility, and stability. Furthermore, the relative standard deviation (RSD) values of Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺ were 3.29, 3.73, 3.11, and 1.97%, respectively. Moreover, the fabricated sensor could sensitively detect HMIs in various environmental samples. The high performance of the sensor was attributed to its sulfur adsorption sites and abundant phenyl rings. Overall, the sensor described herein provides an efficient method for the determination of extremely low concentrations of HMIs in aqueous samples.

From an aluminum oxo cluster to an aluminum oxo cluster organic cage

Presented herein is an example of the conversion of an aluminum oxo cluster (AlOC) to an aluminum oxo cluster organic cage (AlOCOC). We successfully synthesized the first example of an aluminum cluster-based organic cage-Al₁₂ tetrahedral cage via an Al₃ cluster. The use of 4-pyrazolecarboxylic acid plays an important role in the construction of the organic cage. Due to the presence of partially deprotonated ligands, the hydrogen-bonding interactions between the discrete tetrahedra generate porous supramolecular structures. Considering the high porosity and the abundant N-H sites, we further investigated the performance of the material towards iodine capture.

Thiacalix[4]arene-Sandwiched Sandglass-like Ln9 Clusters (Ln = Tb and Eu): Insights into the Selective Luminescence Quenching Properties by p-Nitrobenzene Derivatives

Nonanuclear lanthanide clusters Ln₉ (Ln = Tb and Eu) based on p-tert-butylthiacalix[4]arene (H₄TC4A) have been synthesized by the solvothermal reaction and were structurally determined by single-crystal X-ray diffraction. The framework of Ln₉ can be termed as a sandglass-like structure whose two Ln₄-TC4A polynuclear secondary building units are bridged by one octa-coordinate {Ln(μ₃-O)₈} unit. Efficient TC4A-to-Ln energy transfer was observed for Tb₉ but not for Eu₉. The luminescence quantum yield (QY) of Tb₉ in the solid state at room temperature was determined to be 17.6%, while its highest QY in a methanolic solution (2 × 10^-5 mol/L) is 59.2% upon excitation at 318 nm. The luminescence of Tb₉ was quenched selectively by derivatives of p-nitrobenzene, as demonstrated by the results of photoluminescence and UV-vis titration experiments and supported by density functional theory calculations. We believe that the interactions between the analyte molecules and the pocket of Tb₉ are primarily responsible for the observed quenching. As such, this work represents one of the few examples of utilizing structurally interesting lanthanide cluster complexes as a sensory platform for the recognition of meaningful analytes and portends the further development of lanthanide-calixarene-complex-based functional materials.

Two Cu(i)-based inorganic–organic complexes assembled with polyoxometalate and thiacalix[4]arene for efficient catalytic reactions

Two Cu(i)-based inorganic–organic complexes were synthesized, which can be used as high-efficiency heterogeneous catalysts for ODS and AAC reactions, respectively.

Co9 S8 @CN Composites Obtained from Thiacalix[4]arene-Based Coordination Polymers for Supercapacitor Applications

Metal sulfides have been recognized as promising electrodes for electrochemical energy storage owing to their remarkable electrochemical properties. Here, we demonstrate the preparation of Co₉ S₈ nanoparticles anchored on a carbon matrix (denoted as Co₉ S₈ -X@CN (X=1, 2)) from precursor sources, two 1D infinite coordination polymers 1 and 2. The two polymers were assembled by linking Co₄ -TC4A secondary building blocks (SBUs) with ligands L₁ and L₂ , respectively (H₄ TC4A=p-tert-butylthiacalix[4]arene, L₁ =1,4-bis(2H-tetrazol-5-yl)benzene, L₂ =1,3-bis(2H-tetrazol-5-yl)benzene). The composites obtained from 1D polymers showed different morphologies, that is, the Co₉ S₈ nanoparticles of Co₉ S₈ -1@CN are octahedral with a size of ca. 140 nm, while the lamellar Co₉ S₈ nanoparticles in Co₉ S₈ -2@CN possess different sizes (50-150 nm). The Co₉ S₈ -2@CN immobilized on nickel foam (Co₉ S₈ -2@CN/NF) show better supercapacitive performance than that of Co₉ S₈ -1@CN. Co₉ S₈ -2@CN showed exceptionally high activities, combining higher specific capacitances (445.2 F g^-1 at 2 A g^-1 and 393.9 F g^-1 and 5 A g^-1 ), rate capacity (94.5% retention at 2 A g^-1 ), and long-term stability (79.2% retention at 5 A g^-1 over 1000 cycles). The smaller size and larger BET surface area of Co₉ S₈ -2@CN nanoparticles can improve the electrical conductivity and provide facile pathways for charge transport, thus leading to conspicuous electrochemical performance of Co₉ S₈ -2@CN compared with its Co₉ S₈ -1@CN counterpart.

Assembly of {Co14} nanoclusters from adenine-modified Co4-thiacalix[4]arene units

An adenine-modified Co₄-thiacalix[4]arene unit can serve as a second building unit for fabrication of three Co₁₄ clusters with different structures.