Wheel-Like Icosanuclear Peroxotitanate-A Stable Water-Soluble Catalyst for Oxygen Transfer Reactions

Accurate binding of porous aluminum molecular ring catalysts with the substrate

Metal molecular rings are a class of compounds with aesthetically pleasing symmetry and fundamentally useful properties. The reported work generally focuses on the ring center cavity, and there is little known about those on the ring waist. Herein, we report the discovery of porous aluminum molecular rings and their performance and contribution to the cyanosilylation reaction. We develop a facile ligand induced aggregation and solvent regulation strategy towards AlOC-58NC and AlOC-59NT with high purity, high yield (75% and 70%, respectively) and gram-level scale-up. These molecular rings exhibit a "two-tier" pore feature involving the general central cavity and newly observed equatorial semi-open cavities. AlOC-59NT with two types of one-dimensional channels showed good catalytic activity. The interaction of the aluminum molecular ring catalyst with the substrate has been crystallographically characterized and theoretically confirmed, showing a ring adaptability process that involves the capture and binding of the substrate. This work provides new ideas for the assembly of porous metal molecular rings and to understand the overall reaction pathway involving aldehydes and is expected to inspire the design of low-cost catalysts through structural modifications.

Gradual Size Enlargement of Aluminum-Oxo Clusters and the Photochromic Properties

Metallic clusters, assembled by functional motifs, possess the attribute of regulating the properties by changing inorganic and organic components. In this work, a series of aluminum-oxo clusters, [Al₆O(dmp)₄(Hdmp)₂]·2ⁱPrOH [Al₆-1, H₃dmp = 2,2-bis(hydroxymethyl)propionic acid], [Al₆(H₂thmmg)₆]·2DMF·2H₂O [Al₆-2, H₅thmmg = N-tris(hydroxymethyl)methylglycine], [Al₈(OH)₄(NAP-OH)₁₂(MeO)₇(MeOH)]Cl·7MeCN·3MeOH (Al₈, HNAP-OH = 3-hydroxy-2-naphthoic acid), and [Al₁₀(NA)₁₀(MeO)₂₀] (Al₁₀, HNA = nicotinic acid), were obtained based on different carboxylic acids, realizing metallic ring size enlargement from 5.91 to 9.32 Å. They all exhibit good chemical stability. Importantly, the Al₈ cluster displays obvious photochromic behavior from pale yellow to orange yellow, originating from the generation of photoinduced radicals in the metal-assisted ligand-ligand electron transfer process of 3-hydroxy-2-naphthoic acid (HNAP-OH). This work enriches the metal ring cluster chemistry and reports the example of the aluminum-oxo cluster-based photochromic material, developing a novel system of photochromic materials.

Synthesis, Structure, and Light Absorption Behaviors of Prismatic Titanium-Oxo Clusters Containing Lacunary Lindqvist-like Species

Exploring new structural types of polyoxotitanium clusters (PTCs), especially those containing classical polyoxometalates structures, has always been the focus of research in the field of metal-oxo clusters. In this work, we present the synthesis and characterization of three prismatic PTCs: namely, Ti₈(μ₂-O)₃(μ₄-O)₂(OnPr)₆(HOnPr)₂(L1)₈ (PTC-237; H₂L1 = 3,5-di-tert-butylcatechol), Ti₁₂(μ₂-O)₆(μ₃-O)₈(OnPr)₆(L2)₁₂(L3)₂ (PTC-238; HL2 = 1-adamantanecarboxylic acid, HL3 = 2-picolinic acid), and [Ti₁₈(μ₂-O)₄(μ₃-O)₁₆(μ₅-O)₂(OiPr)₁₈(L3)₈](L3)₂ (PTC-239). Single-crystal X-ray diffraction analyses indicate that the construction of these prismatic PTCs is based on a stepwise interlayer assembly of {Ti₃} and {Ti₄} substructures. The diameters of their core skeletons are in the range between 0.9 and 1.3 nm. In particular, lacunary Linqvist-like {Ti₄} and {Ti₅} building units are found to exist in the structures of PTC-237 and PTC-239. According to the solid-state UV-vis diffuse reflectance measurements, the absorption band of 3,5-di-tert-butylcatecholate-functionalized PTC-237 shifts toward the visible-light region, giving a smaller optical band gap of 1.56 eV in comparison to PTC-238 (3.36 eV) and PTC-239 (3.25 eV).

Functional ligand directed assembly and electronic structure of Sn18-oxo wheel nanoclusters

The bilayer hexagonal Sn₁₈-oxo cluster, as the largest tin-oxo wheel, was constructed by a ligand templating method. Moreover, the ligands also show important effects on electronic structure and third-order nonlinear optical property of the wheel.