Microporous Cyclic Titanium-Oxo Clusters with Labile Surface Ligands

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.

Accurate Regulating of Visible-Light Absorption in Polyoxotitanate-Calix[8]arene Systems by Ligand Modification

With use of a macrocyclic polyphenol, tert-butylcalix[8]arene (TBC[8]), as ligands, a series of TBC[8]-stabilized {Ti₄O₂}clusters, containing penta- and hexacoordinated Ti centers, were synthesized. Such complexes are "core-shell" shaped containing a {Ti₄O₂} core arranged in a zigzag fashion. While outer walls of the clusters are decorated by deprotonated TBC[8], their upper and lower surfaces can be modified by various O- or N-donor ligands, and the ratio of the penta- and hexacoordinated Ti(IV) centers in the {Ti₄O₂} core can be precisely regulated from 4:0, to 3:1, to 2:2, to 1:3, and finally to 0:4. The combined coordination of different ligands in the axial direction shows significant influence on the adsorption of the TBC[8]-Ti₄ system in the visible-light region, and their absorption edge can be precisely regulated from 600 to 700 nm. The above structural functionalization in the TBC[8]-Ti₄ system also tunes their photocatalytic H₂ production activities and oxidative desulfurization ability. Thus, for the first time, by confining the polyoxotitanium cluster in macrocyclic molecules, we provide an example of understanding the structure-property relationship of titanium-oxygen materials by ligand modification.

A Simple Drop-and-Dry Approach to Grass-Like Multifunctional Nanocoating on Flexible Cotton Fabrics Using In Situ-Generated Coating Solution Comprising Titanium-Oxo Clusters and Silver Nanoparticles

Multifunctional nanocoatings have been of central importance in various technological fields, yet their fabrication, especially on flexible substrates, still remains a persistent challenge to date. We herein demonstrate a mild single-step drop-and-dry approach to the in situ growth of hierarchical grass-like nanostructures on flexible cotton fabrics. A precursor solution comprising titanium-oxo clusters [Ti₁₈MnO₃₀(OEt)₂₀(MnPhen)₃] (Phen = 1,10-phenanthroline) and AgNO₃ is employed wherein Ag⁺ cations are in situ-reduced to silver nanoparticles (AgNPs). Drop-casting onto cotton fabrics under mild conditions induces the in situ growth of the heterogeneous grass-like assembly, and each constituent nanofibrous 'grass leaf' incorporates AgNPs both on the surface and embedded in the interior. The hierarchical morphology and heterogeneous composition of these grass-like nanostructures impart the coated cotton fabrics with enhanced antibacterial properties, robust hydrophobicity, and UV-blocking capability, which are features desired in textile materials but lacking in natural cotton.

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.

Ligand-directed assembly engineering of trapezoidal {Ti5} building blocks stabilized by dimethylglyoxime

A facile approach of ligand-directed assembly of trapezoidal {Ti₅} building blocks was successfully established, which gave rise to interesting hybrid clusters including the first molecular assembly of porphyrin photosensitizer and titanium-oxo cluster.

Synthesis of titanium-oxo macrocyles and their catalytic properties for oxidative desulfurization

Titanium-oxo macrocycles with an inner cavity of about 1.2 × 1.2 nm were synthesized and structurally characterized. The structure-dependent catalytic properties towards oxidative desulfurization were studied.

Single-crystal-to-single-crystal desolvation in a Ti32 nanoring cluster

A scarce SCSC structure transformation accompanied with the change of physical/chemical properties was found in a Ti₃₂ nanoring cluster.

Conjugated hybrid films based on a new polyoxotitanate monomer

Electropolymerisation of the novel polyoxotitanate (POT) hexamer [Ti(μ₃-O)(OⁱPr)(TA)]₆ (TA = thiophene-3-acetate) with 3,4-ethylenedioxythiophene (EDOT) gives films of hybrid conjugated copolymer, Poly-(EDOT-POT)s, the morphologies of which are, uniquely, influenced by the electropolymerisation potential.