Titanium Oxo Cluster with Six Peripheral Ferrocene Units and Its Photocurrent Response Properties for Saccharides

Topotactic Conversion of Titanium-Oxo Clusters to a Stable TOC-Based Metal-Organic Framework with the Selective Adsorption of Cationic Dyes

Titanium-oxo cluster (TOC)-based metal-organic frameworks (MOFs) have received considerable attention in recent years due to their ability to expand the application of TOCs to fields that require highly stable frameworks. Herein, a new cyclic TOC formulated as [Ti6O6(OiPr)8(TTFTC)(phen)2]2 (1, where TTFTC = tetrathiafulvalene tetracarboxylate and phen = phenanthroline) was crystallographically characterized. TOC 1 takes a rectangular ring structure with two phen-modified Ti6 clusters as the width and two TTFTC ligands as the length. An intracluster ligand-to-ligand (TTF-to-phen) charge transfer in 1 was found for TOCs for the first time. Compound 1 undergoes topotactic conversion to generate stable TOC-MOF P1, in which the rectangular framework in 1 formed by a TOC core and ligands is retained, as verified by comprehensive characterization. P1 shows an efficient and rapid selective adsorption capacity for cationic dyes. The experimental adsorption capacity (qex) of P1 reaches a value of up to 789.2 mg/g at 298 K for the crystal violet dye, which is the highest among those of various adsorbents. The calculated models are first used to reveal the structure-property relationship of the cyclic host to different guest dyes. The results further confirmed the host MOF structure of P1.

Aggregate assembly of ferrocene functionalized indium-oxo clusters

In this study, we synthesized multi-nuclear indium oxide clusters (InOCs) using 1,1'-ferrocene dicarboxylic acid (H2FcDCA) as the chelating and surface protection ligand. The obtained clusters include the cubane-type heptanuclear InOCs ([In7]) and the sandwich-type thirteen-nuclear InOCs ([In13]). Notably, [In13] represents the highest nuclear number reported within the InOC family. In addition, the presence of labile coordination sites in these clusters allowed for structural modification and self-assembly. A series of [In7] clusters with adjustable band gaps have been obtained and the self-assembly of [In7] clusters resulted in the formation of an Fe-doped dimer, [Fe2In12], and an imidazole-bridged tetramer, [In28]. Similarly, in the case of [In13] clusters, the coordinated water molecules could be replaced by imidazole, methylimidazole, and even a bridged carboxylic acid, allowing the construction of one-dimensional extended structures. Additionally, part of the H2FcDCA could be substituted by pyrazole. This flexibility in replacing solvent molecules offered diverse possibilities for tailoring the properties and structures of the InOCs to suit specific applications.

A ferrocene-modified stable metal-organic framework for efficient CO2 photoreduction reaction

A series of ferrocene-grafted/loaded stable metal-organic frameworks (MOFs), based on the classical NH2-MIL-125(Ti), were prepared to improve the light absorption and photogenerated charge migration of photocatalysts, which can achieve enhanced CO2-to-HCOOH reduction performance. This work highlights the obvious advantage of the modifiability of the MOF structure in optimizing the performance of the photocatalytic CO2RR.

Photoactivation of titanium-oxo cluster [Ti6O6(OR)6(O2C t Bu)6]: mechanism, photoactivated structures, and onward reactivity with O2 to a peroxide complex

The molecular titanium-oxo cluster [Ti₆O₆(OⁱPr)₆(O₂C ^t Bu)₆] (1) can be photoactivated by UV light, resulting in a deeply coloured mixed valent (photoreduced) Ti (iii/iv) cluster, alongside alcohol and ketone (photooxidised) organic products. Mechanistic studies indicate that a two-electron (not free-radical) mechanism occurs in this process, which utilises the cluster structure to facilitate multielectron reactions. The photoreduced products [Ti₆O₆(OⁱPr)₄(O₂C ^t Bu)₆(sol)₂], sol = ⁱPrOH (2) or pyridine (3), can be isolated in good yield and are structurally characterized, each with two, uniquely arranged, antiferromagnetically coupled d-electrons. 2 and 3 undergo onward oxidation under air, with 3 cleanly transforming into peroxide complex, [Ti₆O₆(OⁱPr)₄(O₂C ^t Bu)₆(py)(O₂)] (5). 5 reacts with isopropanol to regenerate the initial cluster (1) completing a closed cycle, and suggesting opportunities for the deployment of these easily made and tuneable clusters for sustainable photocatalytic processes using air and light. The redox reactivity described here is only possible in a cluster with multiple Ti sites, which can perform multi-electron processes and can adjust its shape to accommodate changes in electron density.

Coordination-Delayed-Hydrolysis Method for the Synthesis and Structural Modulation of Titanium-Oxo Clusters

ConspectusAtomically precise titanium-oxo clusters (TOCs) are the structure and reactivity model compounds of technically important TiO₂ materials, which could help build structure-property relationships and achieve property modulation at the molecular level. However, the traditional formation of TOCs has relied on the poorly controllable hydrolysis of titanium alkoxide in the solvent for a long time, limiting the development of TOC structural chemistry to a great extent. In addition, easily hydrolyzable alkoxy groups would be still coordinated on the surface of the TOCs generated by this method, making the clusters sensitive and unstable to the moisture. To achieve controllable preparation of TOCs, we believe it is crucial to attenuate the hydrolysis of titanium ions in the formation process of a cluster. To this end, we have recently applied an effective coordination-delayed-hydrolysis (CDH) strategy for TOC synthesis, which provides powerful tools for tuning their structures.In this Account, at the beginning, a brief introduction to the coordination-delayed-hydrolysis strategy is supplied, and its predominant features for constructing novel TOCs are highlighted. In subsequent sections, we discuss how the applied chelating organic/inorganic ligands (named hydrolysis delayed ligands) influence the hydrolysis process of Ti⁴⁺ ions to form a large family of TOCs with various nuclearities and core structures. Various hydrolysis delayed ligands have been explored, ranging from common O-donor ligands (carboxylate, phenol, or sulfate) to rarely used N-donor ligands (pyrazole) or bifunctional O/N-donor ones (quinoline, oxime, or alkanolamine). Breakthroughs in the symmetry, configuration, and cluster nuclei of TOCs have been accordingly achieved. Then, we show that this CDH method can be used to tune the surface structure of TOCs by modifying functional organic ligands. As a result, the physicochemical properties of TOCs, especially optical band gaps, can be optimized, and their stability under ambient conditions is significantly improved. In addition, we illustrate that the reversible bonds between hydrolysis delayed ligands and Ti ions further allows us to introduce active heterometal ions or clusters upon or inside the Ti-O cores to prepare heterometallic TOCs with unprecedented structures and properties. In particular, noble metal (Ag ions or clusters) has been incorporated into Ti-O clusters for the first time. As a summary, the coordination-delayed-hydrolysis strategy has realized the controllable hydrolysis of Ti⁴⁺ ions to some extent, breaking through the limitations of traditional synthesis methods and producing fruitful results in the field of titanium-oxo clusters. It is believed that this CDH method would also be effective for synthesizing oxo clusters of other easily hydrolyzed metal ions (Al³⁺, Sn⁴⁺, In³⁺, etc.) to afford significant contribution for the cluster community.

Self-Assembly of Chiral Ferrocene-Functionalized Polyoxotitanium Clusters for Photocatalytic Selective Sulfide Oxidation

Here, we systematically studied the self-assembly behavior of chiral polyoxytitanium clusters for the first time. Through the cooperative assembly of ferrocenecarboxylic acid and ketoxime ligands, we successfully incorporated the planar chirality of ferrocene (Fc) into the layered {Ti₅} building blocks. The resulting {Ti₅Fc} clusters can be used as structural units to assemble into large ordered structures in various ways; either a pair of {Ti₅Fc} enantiomers are bridged by organic adhesive to form sandwich structures or two homochiral {Ti₅Fc} units participate in the assembly to form the large clusters. Depending on the assembly modes, the chirality of {Ti₅Fc} can be transferred to large nanoclusters or disappear to form mesostructures. The difference of the assembly modes between the {Ti₅Fc} units can also tune the photoelectric activity of the resulting clusters, which has been verified by using {Ti₁₀Fc-6/7} as catalysts for photocatalytic selective sulfide oxidation. This work not only is an important breakthrough in the study of the self-assembly of chiral nanoclusters but also provides an important reference for understanding of chiral transfer on the nanoscale.

Assembly of Cyclic Ferrocene-Sensitized Titanium-Oxo Clusters with Excellent Photoelectrochemical Activity

The development of crystalline titanium-oxo clusters has made great progress in recent years. However, the geometric assembly of titanium-oxo clusters is still very challenging. Herein, we report the assembly of...

Transition-metal doped titanium-oxo clusters with diverse structures and tunable photochemical properties

Transition metal doping effectively tuned the photochemical properties of titanium-oxo clusters {Ti2Mn4}, {Ti8Co5} and {Ti12Cd5}.

A family of oxime-based titanium-oxo clusters: synthesis, structures, and photoelectric responses

A family of oxime-based titanium-oxo clusters was successfully synthesized, and their photoelectrochemical performances were observed.

Titanium-Oxo Clusters with Bi- and Tridentate Organic Ligands: Gradual Evolution of the Structures from Small to Big

Homometallic titanium oxo clusters are one of the most important groups of metal oxo clusters, with more than 300 examples characterized by X-ray structure analyses. Most of them are uncharged and are obtained by partial hydrolysis and condensation of titanium alkoxo derivatives. The cluster cores, ranging from 3 to >50 titanium atoms, are stabilized by organic ligands. Apart from residual OR groups, carboxylato and phosphonato ligands are most frequent. The article critically reviews and categorizes the known structures and works out basic construction principles by comparing the different cluster types.

Accurate assembly of ferrocene-functionalized {Ti22Fc4} clusters with photocatalytic amine oxidation activity

We report here the synthesis of a ferrocene-functionalized {Ti22Fc4} cluster with a 'dimer-of-clusters' topology, which represents the largest Ti-oxo cluster (TOC) modified with organometallic groups ever reported. The exact assembly path of {Ti22Fc4} can be inferred from its two substructures, {Ti11Fc2} and {Ti5Fc}, which can also be synthesized independently through subtle changes in reaction conditions. Furthermore, we used these clusters as photocatalysts, and have studied, for the first time, the photocatalytic activity of TOCs in the oxidative coupling of amines.

Co-crystal of Ti4Ni2 and Ti8Ni4 clusters with enhanced photochemical properties

A heterometallic cluster with co-crystal arrangement, {Ti₈Ni₄+ Ti₄Ni₂}, which exhibits enhanced photocurrent response and photocatalytic hydrogen evolution activity, has been synthesized.

Tartrate-stabilized titanium–oxo clusters containing sulfonate chromophore ligands: synthesis, crystal structures and photochemical properties

In tartrate-stabilized TOCs, aniline-sulfonate ligands can extend the absorption edge to the visible light region.

Multifunctional Quaternary Phosphorus/Bromoargentate Hybrids: The Achievement of Greenish Blue Luminescence, Repeatable Photocurrent Responses and Durable Antimicrobial Activities with Enhanced Water Stability

Background

The realization of multifunction in one bulk material is fascinating for developing a new generation of devices. Quaternary phosphorus salts were seldom utilized as templates in haloargentate systems, and the hybridization of alkyl(triphenyl)phosphonium with halometallate will be a good strategy for the development of multifunctional material, especially for biological material.

Methods

Under the template of (triphenyl)phosphonium-based quaternary phosphorus salts with different spacer lengths (n=2, 3, 4), three bromoargentate hybrids were constructed via the solution method, ie, (1,2-DBTPP)(Ag₂Br₄) (1), {(1,3-DBTPP)₂(Ag₇Br₁₁)]∙CH₃CN∙H₂O} _n (2), and {[(1,4-DBTPP)(Ag₅Br₇)](CH₃CN)₂∙H₂O} _n (3) (1,2-DBTPP²⁺=ethane-1,2-diylbis (triphenyl)phosphonium, 1,3-DBTPP²⁺=propane-1,3-diylbis (triphenyl)phosphonium, 1,4-DBTPP²⁺=butane-1,4-diylbis (triphenyl)phosphonium)).

Results

The (Ag₇Br₁₁) _n ^4n- chain in 2 is a new type of 1-D bromoargentate chain constructed from cubane-like Ag₄Br₄ nodes, AgBr₄ tetrahedrons and AgBr₃ triangles. Interestingly, by elongating spacer n from 2 to 4, argentophilicity interactions are weakened, and the hydrogen bonds are strengthened. Consequently, their water stabilities and photocurrents are improved, in which the Ag-4d/Br-4p to π* anti-bonding orbital of the quaternary phosphorus transfer is facilitated. Furthermore, the greenish blue emissions can be detected. Finally, high inhabitation rates against Streptococcus mutans and Candida albicans can be observed in 2 and 3.

Conclusion

In all experiments, by elongating the spacer lengths of quaternary phosphorus salts, multifunctions were integrated in the quaternary phosphorus/bromoargentate hybrids, including greenish blue luminescence, repeatable photocurrent responses and durable antimicrobial activities with enhanced water stability. This work could provide a theoretical guide for the design of new biologically multifunctional materials.

Cluster-to-cluster charge transfer in a compound with a co-crystallized dye-anchored Ti6 cluster and a classical Ti12 cluster

A new titanium-oxo cluster (TOC) with a co-crystallized dye-anchored Ti₆ cluster and a classical Ti₁₂ cluster was isolated. The Ti₆ cluster is anchored by mixed dyes of photoactive triphenylamine and catechol. This is the first co-crystallized neutral TOC. TOC (Ti₆) to TOC (Ti₁₂) charge transfer was studied using electronic spectra and DFT calculations based on their precise structures. The improved photocurrent response properties of the TOC-modified TiO₂ electrode are due to the influence of charge transfer and co-condensation of the Ti₆ and Ti₁₂ clusters. The photocurrent response properties of the compound for fructose and glucose were tested.

Synthesis, structural and physicochemical characterization of a new type Ti6-oxo cluster protected by a cyclic imide dioxime ligand

A new type of Ti₆-oxo cluster with a structural motif TiIV6O₅ was synthesized of which the cyclo-Ti₃ metallic cores exhibit metallaromaticity.

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.

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.

Structures and photophysical performances of (fluoro)salicylate stabilized polyoxo-titanium clusters

The introduction of fluorine in salicylic acid yielded different polyoxo-titanium clusters with distinct photophysical properties.

Lead-carboxylate/polyiodide hybrids constructed from halogen bonding and asymmetric viologen: structures, visible-light-driven photocatalytic properties and enhanced photocurrent responses

Two lead-carboxylate/polyiodide hybrids constructed from halogen bonding and asymmetric viologen have been synthesized, which exhibit efficient photocatalytic degeneration performances.

A 4-dimethylaminobenzoate-functionalized Ti6-oxo cluster with a narrow band gap and enhanced photoelectrochemical activity: a combined experimental and computational study

The D–π-A structured dye 4-dimethylaminobenzoate (DMABA) functionalized Ti₆-oxo cluster exhibits a remarkably reduced band gap of ∼2.5 eV.

A ferrocenecarboxylate-functionalized titanium-oxo-cluster: the ferrocene wheel as a sensitizer for photocurrent response

A ferrocenecarboxylate-functionalized titanium-oxo cluster [Ti₆(μ₃-O)₆(OiPr)₆(O₂CFc)₆] was synthesized, in which the ferrocene wheel performs as a sensitizer for photocurrent response.