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

Thiacalixarenes are intriguing ligands that have attracted sustained interest because of their changeable conformations and excellent coordination ability. Thiacalix[4]arene analogues, which can bind metal ions to form modular second building units, are capable of constructing molecular-based functional materials with defined structures and various applications via directional coordination assembly. Due to rich metal-sulfur bonds, thiacalix[4]arene-based molecular clusters also exhibit diverse properties compared to other clusters. In particular, the combination of thiacalixarenes with currently popular molecular architectures, such as high-nuclearity clusters and coordination cages, has shown special catalytic performances. In this perspective, the latest advances in catalytic applications of thiacalix[4]arene-based molecular clusters, including molecular clusters themselves as catalysts and coordination cages serving as reaction vessels encapsulating metal nano-components for catalysis, are highlighted.

Coordination polymers with embedded recognition sites: lessons from cyclotriveratrylene-type ligands

Coordination polymers with molecular recognition sites are assembled using cyclotriveratrylene ligands. Many show differential guest-spaces with host and lattice sites available, however common host–guest and self-inclusion motifs can block sites.

Coordination-Assembled Molecular Cages with Metal Cluster Nodes

Molecular cages have attracted great attention because of their fascinating topological structures and well-defined functional cavities. These discrete cages were usually fabricated by coordination assembly approach, a process employing directional metal-ligand coordination bonds due to the nature of the divinable coordination geometry and the required lability to encode dynamic equilibrium/error-correction. Compared to these coordination molecular cages with mononulcear metal-nodes, an increasing number of molecular cages featuring dinuclear and then polynuclear metal-cluster nodes have been synthesized. These metal-cluster-based coordination cages (MCCCs) combine the merits of both metal clusters and the cage structure, and exhibit excellent performances in catalysis, separation, host-guest chemistry and so on. In this review, we highlight the syntheses of MCCCs and their potential functions that is donated by the metal-cluster nodes.

Structure and redox tuning of gas adsorption properties in calixarene-supported Fe(ii)-based porous cages

We describe the synthesis of Fe(ii)-based octahedral coordination cages supported by calixarene capping ligands. The most porous of these molecular cages has an argon accessible BET surface area of 898 m2 g-1 (1497 m2 g-1 Langmuir). The modular synthesis of molecular cages allows for straightforward substitution of both the bridging carboxylic acid ligands and the calixarene caps to tune material properties. In this context, the adsorption enthalpies of C2/C3 hydrocarbons ranged from -24 to -46 kJ mol-1 at low coverage, where facile structural modifications substantially influence hydrocarbon uptakes. These materials exhibit remarkable stability toward oxidation or decomposition in the presence of air and moisture, but application of a suitable chemical oxidant generates oxidized cages over a controlled range of redox states. This provides an additional handle for tuning the porosity and stability of the Fe cages.

Thiacalixarene-Supported Irregular Co26 and Ni28 High-Nuclearity Clusters with Pyridyl-Diphosphonates: Strategies to Create Active Metal Sites and Fabricate Multicomponent Materials

Two new irregularity high-nuclearity clusters [Co₂₆(TC4A)₆(HL)₄Cl₄(HCOO)₄(CH₃O)₂(OH)₂(DMF)₁₀(H₂O)₅] (+ solvent) (Co₂₆) and [Ni₂₈(TC4A)₆(HL)₆(PO₄)₂(μ₃-O)₂Cl₂(CH₃OH)₁₄(H₂O)₂(DMF)₈][(CH₃NH₂CH₃)₄] (+ solvent) (Ni₂₈) have been solvothermally synthesized by p- tert-butylthiacalix[4]arene (H₄TC4A), transition metals (CoCl₂·6H₂O/NiCl₂·6H₂O), and 1-hydroxy-2-(3-pyridinyl)ethylidene-1,1-diphosphonic acid (H₅L). The clusters were structurally characterized by single crystal X-ray diffraction, PXRD, TGA, and FT-IR spectrum and Raman spectrum. Co₂₆ features a rodlike Co₂₆ core constructed by six Co₄-TC4A secondary building units (SBUs) and four HL^4- with two extra cobalt ions. Ni₂₈ cluster represents a flowerlike Ni₂₈ core built from six Ni₄-TC4A SBUs, six HL^4-, and four additional nickel ions. The multidentate risedronic acid displaying various new coordination mode bonds with SBUs to assemble two nanoclusters that enable high density possible coordinatively unsaturated metal sites (PCUMSs). Co₂₆ and Ni₂₈ clusters can be directly dispersed on carbon paper (CP) and showed extraordinary oxygen evolution reaction (OER) activity due to the larger exposed liable coordination active metal sites. The thermodecomposition of both nanoclusters at different temperatures afforded serial multicomponent complexes.

A 2D metal-thiacalix[4]arene porous coordination polymer with 1D channels: gas absorption/separation and frequency response

A 2D layered structure {[Co4(TC4A)Cl](L)2][(CH3CH2)4N]}n (+solvent)(1) has been solvothermally synthesized by assembly of Co4-TC4A (H4TC4A = p-tert-butylthiacalix[4]arene) subunits and L (H2L = 4-(1H-tetrazol-5-yl)benzoic acid) ligands. The layers arranged in an edge-to-edge (AAAA) manner, which represented the only example of 2D porous coordination polymers (PCPs) with 1D uniform channels of metal-thiacalix[4]arene. The activated PCP 1 exhibited high selectivity for C3H8/C2H6, C3H6/C2H4, and C3H8/C2H4, which makes it a competitive porous material for C3/C2 alkane and/or olefin separations. Frequency response investigations for C3H8 and C2H6 indicated that the 1D channels and inter-layer voids of the activated crystalline samples are primarily responsible for the observed gas adsorption and separation performances.

A monomeric bowl-like pyrogallol[4]arene Ti12 coordination complex

Herein, an unprecedented monomeric bowl-like coordination complex, Ti₁₂PgC₃ (PgC₃ = C-propylpyrogallol[4]arene), has been successfully synthesized. To the best of our knowledge, Ti₁₂PgC₃ not only presents the first pyrogallol[4]arene-based titanium coordination complex, but also the highest nuclearity titanium coordination complex in the metal-calixarene system. In addition, this titanium coordination complex can effectively degrade the methylene blue (MB) dye under sunlight.

Thiacalix[4]arene-supported tetradecanuclear cobalt nanocage cluster as precursor to synthesize CoO/Co9S8@CN composite for supercapacitor application

A new high nuclearity N,S-co-rich Co₁₄ cage cluster was used as a precursor to synthesize CoO/Co₉S₈@CN composites for applications in supercapacitors.

A metal-calixarene coordination nanotube with 5-(pyrimidin-5-yl)isophthalic acid

A coordination nanotube with truncated metal-calixarene octahedra exhibited a good ability to separate CH₄ from C₂H₆ and from C₃H₈.

2D networks of metallo-capsules and other coordination polymers from a hexapodal ligand

2D M₃L₂ coordination polymers (M = Re(i), Cu(ii), Co(ii), Ni(ii)) feature metal-linked M₆L₂-cages, and the Re(i) material absorbs iodine.

Organoamine-induced isomerism of calixarene-based complexes: from 1D to 2D

Two isomers of the calixarene-based cobalt complex [Co₄Cl(TC4A)(BCPT)₂]⁻ (H₄TC4A = p-tert-butylthiacalix[4]arene; H₂BCPT = 3,5-bis (4′-carboxy-phenyl)-1,2,4-triazole) were obtained under the solvothermal conditions with tetramethylammonium/tetraethylammonium hydroxide (CIAC-236) and triethylamine (CIAC-237). Single crystal X-ray diffraction reveals that CIAC-236 has a 1D zigzag aggregate constructed by bridging the shuttlecock-like Co₄–TC4A secondary building units (SBUs) with two pairs of opposite V-shaped BCPT ligands while CIAC-237 possesses a 2D layer assembly with each Co₄–TC4A SBU bonded by four BCPT ligands in a same direction (clockwise or counterclockwise), which indicates that different shapes of the organoamines lead to different assembly of the BCPT ligands and the formation of different extended aggregates. For comparison, only the 1D structure ([Fe₄Cl(TC4A)](BCPT)₂]⁻, CIAC-238) was obtained for the iron complexes with all these three organoamines, which would be attributed to different property and coordination of iron element. Magnetic properties of all these three compounds were studied.

Two isomers of the calixarene-based cobalt complex, 1D aggregate and 2D network, were obtained with different organoamine templates.

A series of cobalt and nickel clusters based on thiol-containing ligands accompanied by in situ ligand formation

We report a series of cobalt and nickel clusters based on thiol-containing ligands, 2-mercaptobenzothiazole (HMBT) and 2-mercaptobenzimidazole (H₂MBI), accompanied by in situ ligand transformation of HMBT. The magnetic properties of the cobalt clusters have been investigated.