Supramolecular Chemistry of Titanium Oxide Clusters

Abstract

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.

S-Scheme Bi-oxide/Ti-oxide Molecular Hybrid for Photocatalytic Cycloaddition of Carbon Dioxide to Epoxides

“…The two components are linked by 12 μ 3 -O and 6 μ 4 -O. The Ti 18 O 26 shell contains four cyclic Ti 6 O 6 apertures, which have been observed in a few TOCs such as [CsTi 12 O 18 (OH 2 ) 24 Ser 6 ] 13+ , Ti 16 Pb 5 O 16 Bz 2 (OCH 3 ) 40 , and Ag 2 Ti 12 O 14 Bz 14 (OMe) 8 , in which the heterometal ions like Cs + , Pb 2+ , and Ag + are trapped “in pocket” by the Ti 6 O 6 rings . Each Ti 6 O 6 ring of Ti 18 Bi 4 confines a Bi 3+ ion (Figure D).…”

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

“…In this respect, however, much less attention has been devoted to titanium-oxide clusters or polyoxotitanates (POTs). − POTs are widely identified as the molecular analogue of TiO 2 , and the latter is renowned for the light-harvesting properties and related applications. With the Ti–O–Ti motif resembling the C–O–C group and the outstanding structural versatility, POT has been expected to function similarly as organic hosts like crown ether. , Recent years have indeed witnessed some significant progresses. Inorganic ions or molecules (such as I – , , K + , Cs + , Br – , and H 2 O) were found to be accommodated by POTs.…”

“…With the Ti− O−Ti motif resembling the C−O−C group and the outstanding structural versatility, POT has been expected to function similarly as organic hosts like crown ether. 29,30 Recent years have indeed witnessed some significant progresses. Inorganic ions or molecules (such as I − , 31,32 K + , 33 Cs + , 34 Br − , 35 and H 2 O 36 ) were found to be accommodated by POTs.…”

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

“…It could be envisaged that an interlocked system constructed with them may exhibit promising applications associated with the properties of the TOCs. Using the neutral {Ti 8 O 8 ( t BuCO 2 ) 16 } and linear alkylammonium cations as the threads, Winpenny et al constructed a series of rotaxanes. , However, these titanium oxo carboxylate-passivated assemblies were synthesized by nonaqueous solvothermal processes, were prone to hydrolysis and oxidation, and could be handled only under nonaqueous conditions. − By contrast, Fu et al obtained a [ Ti 8 ·DETA] (DETA = diethylenetriamine) complex from acidic aqueous Ti 4+ /SO 4 2– solutions, of which the linear DETA threads the Ti 8 ring . However, because of the lack of stoppers of DETA, [ Ti 8 ·DETA] could not be regarded as an interlocked system.…”

“…This may be a new branch of supramolecular chemistry. Because the syntheses, structures, and properties of aqueous TOCs are greatly influenced by the alkylammonium threads, , it may be possible to prepare more mechanical interlocked assemblies with good water solubility/stability through optimization of the amines. The functionalities of these molecular motors are also to be studied in the future.…”