Host-Guest and Photophysical Behavior of Ti8 L12 Cube with Encapsulated [Ti(H2 O)6 ] Species

An ultrastable Ti-based metallocalixarene nanocage cluster with photocatalytic amine oxidation activity

Polyhedral metallocalixarene nanocage clusters based on pure Ti(IV) ions are to our knowledge unknown hitherto. Herein we report the first Ti(IV)-based metallocalixarene nanocage cluster by assembling a [Ti₁₃O₁₄] cage with six t-butylcalix[4]arene molecules. Notably, the cluster exhibits extraordinary stability in high-concentration acid/alkali solutions and can act as a stable photocatalyst to catalyze the oxidation of ammonia to imines.

Inorganic acid influenced formation of Ti26 and Ti44 oxysulfate clusters with toroidal and capsule structures

We herein report the discovery of inorganic toroidal and capsule titanium oxysulfate clusters by ionothermal synthesis. The ratio between geometrically different anions (tetrahedral SO₄^2-vs. pseudo-tetrahedral PO₃^3-) shows an interesting influence on cluster structure formation.

Photoinduced host-to-guest electron transfer in a self-assembled coordination cage

Light–powered host–guest charge transfer (HGCT) is shown for a coordination cage based on electron-rich phenothiazines, containing an anthraquinone acceptor as guest. Transient absorption spectroscopy and spectroelectrochemistry data is presented.

Modification of Multi-Component Building Blocks for Assembling Giant Chiral Lanthanide-Titanium Molecular Rings

Building blocks with multiple components are promising for the synthesis of complex molecular assemblies, but are rarely available. Herein, we report a modification procedure for a multi-component building block [Ln₃ Ti(HSA)₆ (SA)₄ (H₂ O)]^- ({Ln₃ Ti-SA}, H₂ SA=salicylic acid, Ln=Eu/Gd) to form new building blocks {Ln₃ Ti_x -MSA} (H₂ MSA=5-methoxysalicylic acid, x=1, 2, 3) by constructing [Ti(MSA)₃ ]^2- units. The obtained {Ln₃ Ti_x -MSA} can further assemble into a chiral Ln₂₂ Ti₁₄ ring with the formulae [Eu₂₂ Ti₁₄ (MSA)₄₈ (HMSA)₂₂ (CH₃ COO)₄ (H₂ O)₁₀ (iPrOH)] and [Gd₂₂ Ti₁₄ (MSA)₄₆ (HMSA)₂₆ (CH₃ COO)₄ (H₂ O)₈ ]. Parallel experiments without Ti⁴⁺ result in linear Ln chains. Detailed analysis shows that the [Ti(MSA)₄ ]^4- unit makes the originally variable Ln chains become available building blocks and the modified [Ti(MSA)₃ ]^2- further triggers interesting chiral-sorting behavior. Finally, the electronic adsorption and magneto-optic responses of these molecular rings are investigated.

Coordination Assembly of Tetrahedral Zr4(embonate)6 Cages with Eu3+ Ions

Herein we systematically investigated the coordination assembly behavior of Zr₄L₆ cages with Eu³⁺ ions at room temperature. Through adjustment of the concentration of Eu salt and changes of the type and molar ratio of the solvent, a series of Zr₄L₆-Eu structures with different structure dimensionalities have been synthesized and structurally characterized. In addition, we also studied the optical properties of these materials in detail, including the fluorescent and third-order nonlinear-optical properties. Most notably, a 2D layer structure with a strong aromatic π···π-stacking force exhibits a good optical-limiting effect.

Syntheses, structural modulation, and slow magnetic relaxation of three dysprosium(III) complexes with mononuclear, dinuclear, and one-dimensional structures

Three mononuclear, dinuclear and one-dimensional dysprosium(III) complexes based on 3-azotriazolyl-2,6-dihydroxybenzoic acid (H₄ATB) of [Dy(H₃ATB)₃]·3H₂O (1), [Dy₂(H₂ATB)₂(H₂DHB)₂(H₂O)₄]·2CH₃CN·5H₂O (2), and [Dy₂(H₂ATB)₂(DCB)(DMF)₂(H₂O)₂]·4DMF (3) were synthesized and structurally characterized by X-ray single crystal diffraction (H₃DHB = 2,6-dihydroxybenzoic acid, H₂DCB = 1,4-dicarboxybenzene). Complex 1 was used as a precursor to synthesize complexes 2 and 3, and 2 was further used to synthesize 3. Complex 1 is a mononuclear complex, in which the Dy(III) ion is in a nine-coordinated structure surrounded by three tridentate chelate H₃ATB^- ligands. Complex 2 displays a dinuclear structure bridged by two μ₂ carboxyl groups of two H₂DHB^- ligands and two μ_1,1-O atoms from the phenolic hydroxyl groups of two H₂ATB^2- ligands. Complex 3 shows a one-dimensional structure formed by two bridging DCB^2- ligands. The magnetic measurements were performed on three complexes 1-3, and they showed different magnetic behavior. Complex 1 shows a field-induced slow magnetic relaxation. Complexes 2 and 3 display distinct slow magnetic relaxation under zero dc field with energy barriers (U_eff) of 26(2) cm^-1 and 11(1) cm^-1, respectively. The magnetic behavior of three complexes 1-3 was investigated by ab initio calculations.

Polyoxotitanate Molecular Cage Featuring Four Types of Ethylenediamines: Formation Mechanism Insight from Host-Guest Interaction and Crystallographic Study

Titanium-oxide or polyoxotitanate clusters are a new type of inorganic host materials that can encapsulate inorganic molecules or ions. We report herein a (NH₄)₄(enH₂)[Ti₁₈O₂₇(PhCOO)₂₄(en)₉] molecular cage (Ti₁₈) that encapsulates an entire organic ethylenediamine (en) ion. A thorough investigation has revealed the extraordinary versatility of en. Besides being a guest cation, it also functions as chelating and bridging ligand. It balances the charge of the negative Ti₁₈ cage and facilitates the deprotonation of benzoic acid at the early stage of the reaction as well. DFT calculation and a derivative of Ti₁₈ with open sites at its equatorial position shed further light on the formation mechanism. Ti₁₈ strongly absorbs visible light as a result of en coordination, and it exhibits superior photocatalytic activity compared to anatase TiO₂.

Tetrahedral Geometry Induction of Stable Ag-Ti Nanoclusters by Flexible Trifurcate TiL3 Metalloligand

A series of increasingly large silver nanoclusters with a varied combination of Archimedean and/or Platonic solid arrangements was constructed using a flexible trifurcate TiL₃ (L = Salicylic acid or 5-fluorosalicylic acid) metalloligand: Ag₄@Ag₄@Ti₄ (PTC-85), Ag₁₂@Ti₄ (PTC-86), Ag₄@Ag₆@Ag₁₂@Ti₄ (PTC-87), Ag₆@Ag₂₄@Ag₁₂@Ti₄ (PTC-88), and Ag₁₂@Ag₂₄@Ti₄ (PTC-89). The silver nanoclusters are each capped by four TiL₃ moieties, thereby forming {Ti₄} supertetrahedra with average edge lengths ranging from ∼8.12 Å to ∼17.37 Å. Such {Ti₄} moieties further induce the tetrahedral geometry of the encapsulated silver nanoclusters. These atomically precise metallic clusters were found to be ultrastable with respect to air for several months, and to water for more than 3 days, due to the stabilizing effects of the TiL₃ metalloligand. Moreover, the obtained clusters exhibit nonlinear optical (NLO) effects in optical limiting tests and also temperature-dependent photoluminescent properties. This work provides an interesting metalloligand method not only to induce the spatial growth of metallic clusters to achieve highly symmetric structures, but also to enhance their stability which is crucial for future application.

Supramolecular Co-assembly of the Ti8L12 Cube with [Ti(DMF)6] Species and Ti12-Oxo Cluster

Titanium-based coordination cages are fascinating in the field of supramolecular and photophysical chemistry. Herein, we address the unprecedented supramolecular co-assembly arrangement of a cubic Ti₈L₁₂ cage with [Ti(DMF)₆] species and Ti₁₂-oxo cluster, contributing to the cocrystals of {Ti₈L₁₂ + Ti(DMF)₆} (PTC-116) and {Ti₈L₁₂ + Ti₁₂-oxo} (PTC-117). The ESI-MS and ¹H NMR measurements reveal their stability in solution. The photophysical properties of these supramolecular complexes in solution, including light absorption and photoluminescent behaviors, were further investigated.

One-Pot and Postsynthetic Phenol-Thermal Synthesis toward Highly Stable Titanium-Oxo Clusters

The synthetic approach plays a crucial role for the exploration and optimization of functional materials. As the molecular models of titanium dioxide, polyoxo-titanium clusters have undergone rapid development over past decade. Unfortunately, many of them are unstable, especially in aqueous environments, greatly limiting their applications in catalysis and environmental fields. In this work, we report a novel phenol-thermal approach toward the construction of highly stable polyoxo-titanium clusters. In addition to the traditional one-pot procedure, the phenol-thermal synthesis can also be used as a postsynthetic pathway to modify the alcohol terminated titanium-oxo clusters. During the modification in phenol, Ti-O core structures consisting entirely of 6-coordinated Ti^IV centers can be retained. Nevertheless, isopropanol terminated 5-coordinated Ti^IV centers are not stable and reconstructed to 6-coordinated Ti^IV centers during the phenol-thermal modification to form new Ti-O clusters. Physical attribute studies confirm that the obtained phenolic clusters generally display much better stability and stronger visible light absorption than isopropanol stabilized clusters with identical or similar cores. Therefore, phenol can not only offer a suitable solution environment for the construction of new cluster structures but also provide robust protection for the cluster cores and also an efficient method to enhance their visible light responses.