New inorganic discrete 8-membered wheel clusters: Organically directed titanium sulfate supermolecules

Revitalisation of group IV metal-oxo clusters: synthetic approaches, structural motifs and applications

Group (IV) metal oxo clusters represent a unique family of molecular species that are increasingly being utilized in applications ranging from catalysis and materials chemistry to electronics, and sensors. These clusters exhibit distinctive structural features, chemical reactivity, and electronic structure. Nevertheless, their full potential has yet to be fully realized due to the lack of deeper understanding regarding their structure and formation mechanisms, inherent traits, and intricacies in their design, which could ultimately enable significant customization of their properties and overall behaviour. Considering the recently observed reignited interest in the chemistry of group IV molecular species, the scope of this article is to bring to the readers the main chemical characteristics of the family of titanium, zirconium, and hafnium-based clusters, their structural features and their potential in future applications.

Assembly of Interlocked Superstructures with a Titanium Oxide Molecular Ring in Water

[2]Catenane, [2]rotaxane, and [2]pseudorotaxane based on a cyclic titanium oxide cluster, [Ti₈O₈(SO₄)₁₆]^16- (Ti₈), and cyclic/linear alkylammonium cations are reported. Their syntheses, structures, spectroscopy, and stability in water were studied. These molecules were synthesized from and remained intact upon redissolution in acidic water. Hence, the cluster Ti₈ is a promising metal oxide ring that can be used as an inorganic analogue of crown ether to assemble inorganic-organic hybrid mechanical interlocked supramolecular assemblies in water.

Macrocyclic Inorganic Tin-Containing Oxo Clusters: Heterometallic Strategy for Configuration and Catalytic Activity Modulation

In this work, the first examples of inorganic macrocyclic tin-oxo clusters which are stabilized by sulfate ligands are reported. As determined by X-ray diffraction and photoelectron spectroscopy analyses, the prepared inorganic Sn₁₀ -oxo cluster displays interesting mixed valence behaviors, with 8 Sn⁴⁺ located at the cyclic skeleton and two Sn²⁺ encapsulated in the center. When further introducing Ti⁴⁺ and In³⁺ ions to the synthetic systems, heterometallic Sn₂ Ti₆ and SnIn₅ Ti₆ complexes with Ti₆ (SO₄ )₉ and SnIn₅ (SO₄ )₁₂ macrocyclic skeletons were prepared whose configuration and packing models were affected by the ionic radius of incorporated metals. Moreover, comparative CO₂ reduction experiments confirm that such heterometallic composition can significantly improve the catalytic activities of these inorganic macrocyclic oxo clusters. This work represents a milestone in constructing inorganic tin complexes and also macrocyclic metal oxo clusters with tunable configurations and properties.

Supramolecular Chemistry of Titanium Oxide Clusters

Titanium oxide clusters (TOCs) have been emerging as a new type of inorganic molecular entities of supramolecular chemistry. Herein, a perspective on the structures and functionalities of TOCs over the past three decades is given and the paramount roles of TOCs in serving supramolecular chemistry are demonstrated. Four types of supramolecular assemblies based on TOCs are reviewed, namely, TOC hosts for ion inclusion, mechanically interlocked molecular systems built from cyclic TOCs, reactivities of surface sites toward ligand exchange, and hierarchical structures of TOCs. The principles and advantages of TOCs toward each application are fully discussed, along with structural analyses. Following this path, more functional TOC-based supramolecular systems may be designed and synthesized in the future, which, in turn, will certainly enhance research into both supramolecular and coordination chemistry of titanium.

Effects of organic ammonium cations on the isolation of {Ti4} cyclic clusters from water: an 17O NMR study

For the preparation of aqueous Ti-oxo clusters (TOCs) without organic ligands, organic ammonium cations (OACs) are important, but the mechanism is obscure. Here, the Ti⁴⁺/SO₄^2- system was chosen as a model to investigate the roles of OACs. Three {Ti₄} clusters were isolated from this system with different cationic additives. Structural analysis revealed a structural role of OACs: the hierarchically ordered array of the OACs in the organic layers was responsible for the stability and formation of crystalline precipitates. ¹⁷O NMR spectroscopy was used to study the interactions of OACs and SO₄^2- with the Ti-oxo species in water under highly acidic conditions. SO₄^2- enhanced the condensation of Ti⁴⁺ by binding to the TOC species. OACs could not enhance the condensation of Ti⁴⁺ but could change the solution speciation and especially promote the formation of {Ti₁₈O₂₇} clusters. We speculate that OACs interact with the cationic/neutral TOCs through anionic bridges to change the speciation. Under the synthetic conditions of {Ti₄}, {Ti₁₈O₂₇} is the native TOC in solutions but {Ti₄} is not.

Synthetic strategies, diverse structures and tuneable properties of polyoxo-titanium clusters

A review of polyoxo-titanium clusters (PTCs), with an emphasis on synthetic methodologies, diverse structures, tuneable optical properties and potential applications.