Water-soluble neutral octahedral chalcogenide tungsten and molybdenum {MQ} clusters with P(CHCONH) ligand.

Developing the chemistry of octahedral chalcogenide molybdenum and tungsten cluster complexes in the context of applications in biology and medicine, in this work a series of water-soluble neutral cluster complexes [{MQ}(P(CHCONH))] (M = Mo, W; Q = S, Se) have been obtained by simultaneous replacement of inner and terminal halide ligands in [{MI}I] with chalcogenide and organic phosphine ligands and characterized by single-crystal X-ray diffraction analysis, H and P NMR spectroscopies, elemental analysis, and UV-vis spectroscopy. The amide groups of the organic ligands, on the one hand, contribute to the solubility of the resulting clusters in water and, on the other hand, are able to form an extensive network of hydrogen bonds, leading to the crystallization of the complexes from aqueous solutions. Despite this fact, the complexes have sufficient solubility and stability in aqueous solutions, which made it possible to demonstrate their low cytotoxicity on Hep-2 cells (IC were not reached even at concentration up to 4 mM).

Octahedral molybdenum iodide clusters with pyrazole or pyrazolate ligands.

Due to the combination of useful physicochemical properties (luminescence, X-ray contrast, .), octahedral molybdenum halide cluster complexes [MoXL] have been the subject of active investigation during the last decades. The most common methods for synthesizing new compounds with organic ligands involve the use of silver salts of organic acids or the substitution of terminal methylate ligands.

PEGylation of Terminal Ligands as a Route to Decrease the Toxicity of Radiocontrast Re-Clusters.

The development of novel radiocontrast agents, mainly used for the visualization of blood vessels, is still an emerging task due to the variety of side effects of conventional X-ray contrast media. Recently, we have shown that octahedral chalcogenide rhenium clusters with phosphine ligands-NaH[{ReQ}(P(CHCOO))] (Q = S, Se)-can be considered as promising X-ray contrast agents if their relatively high toxicity related to the high charge of the complexes can be overcome. To address this issue, we propose one of the most widely used methods for tuning the properties of proteins and peptides-PEGylation (PEG is polyethylene glycol).

Improved Synthesis of (TBA)[WBr] Paving the Way to Further Study of Bromide Cluster Complexes.

Octahedral cluster complexes of molybdenum and tungsten, [MXY] (M = Mo, W; X, Y = Cl, Br, I), are promising active components in various fields, including biomedicine and solar energy. Cluster complexes draw considerable attention due to their X-ray opacity, red/near-IR luminescence, and ability to convert triplet molecular oxygen to active singlet oxygen under UV and visible irradiation. Among the octahedral cluster complexes of molybdenum and tungsten, compounds with a {WBr} core are the least studied.

Unusual Square Pyramidal Chalcogenide Mo Cluster with Bridging Pyrazolate-Ligands.

The family of chalcogenide molybdenum clusters is well presented in the literature by a series of compounds of nuclearity ranging from binuclear to multinuclear articulating octahedral fragments. Clusters actively studied in the last decades were shown to be promising as components of superconducting, magnetic, and catalytic systems. Here, we report the synthesis and detailed characterization of new and unusual representatives of chalcogenide clusters: square pyramidal complexes [{Mo(μ-Se)(μ-Se)(μ-pz)}(pzH)] (pzH = pyrazole, i = inner, t = terminal).

Water-Soluble Chalcogenide W-Clusters: On the Way to Biomedical Applications.

Despite the great potential of octahedral tungsten cluster complexes in fields of biomedical applications such as X-ray computed tomography or angiography, there is only one example of a water-soluble WQ-cluster that has been reported in the literature. Herein we present the synthesis and a detailed characterization including X-ray structural analysis, NMR, IR, UV-Vis spectroscopies, HR-MS spectrometry, and the electrochemical behavior of two new cluster complexes of the general formula WQL with phosphine ligands containing a hydrophilic carboxylic group, which makes the complexes soluble in an aqueous medium. The hydrolytic stability of the clusters' aqueous solutions allows us to investigate for the first time the influence of W-clusters on cell viability.

Self-Assembled Microporous M-HOFs Based on an Octahedral Rhenium Cluster with Benzimidazole.

Substitution of apical halide ligands in [{ReSe}X] (X = Cl, Br) by benzimidazole (bimzH) accompanied by a self-assembly process leads to the formation of microporous Re-based hydrogen-bonded organic frameworks (Re-HOFs) constructed on N-H···X hydrogen bonds and π-π-stacking interactions between bimzH ligands. Re-HOFs demonstrate sorption properties with a Brunauer-Emmett-Teller surface area of up to 443 m g and luminescence with a quantum yield and an emission lifetime of up to 0.16 and 16 μs, respectively.

"Host in Host" Supramolecular Core-Shell Type Systems Based on Giant Ring-Shaped Polyoxometalates.

Herein, we show how the chaotropic effect arising from reduced molybdate ions in acidified aqueous solution is able to amplify drastically weak supramolecular interactions. Time-resolved Small Angle X-ray Scattering (SAXS) analysis suggests that molybdenum-blue oligomeric species form huge aggregates in the presence of γ-cyclodextrin (γ-CD) which results in the fast formation of nanoscopic {Mo }-based host-guest species, while X-ray diffraction analysis reveals that the ending-point of the scenario results in an unprecedented three-component well-ordered core-shell-like motif. A similar arrangement was found by using preformed hexarhenium chalcogenide-type cluster [Re Te (CN) ] as exogenous guest.

Cyclodextrin-Assisted Hierarchical Aggregation of Dawson-type Polyoxometalate in the Presence of {ReSe} Based Clusters.

The association of metallic clusters (CLUS) and polyoxometalates (POM) into hierarchical architectures is achieved using γ-cyclodextrin (γ-CD) as a supramolecular connector. The new self-assembled systems, so-called CLUSPOM, are formed from Dawson-type polyoxometalate [PWO] and electron-rich rhenium clusters. It is worth noting that a cluster-based cation [{ReSe}(HO)] on one hand and a cluster-based anion on the other hand [{ReSe}(CN)] can be associated with the anionic POM.

Soluble Molecular Rhenium Cluster Complexes Exhibiting Multistage Terminal Ligands Reduction.

Substitution of terminal halide ligands of octahedral rhenium cluster complexes [ReQX] in a melt of 4,4'-bipyridine (bpy) led to us obtaining four new compounds with the general formula -[ReQ(bpy)X] (Q = S or Se; X = Cl or Br) in high yield. In contrast to most of the known molecular rhenium cluster complexes with heteroaromatic terminal ligands, compounds - are soluble in organic solvents. This made it possible to carry out a detailed characterization of the new compounds both in solids and in solutions.

Hexamolybdenum Clusters Supported on Exfoliated h-BN Nanosheets for Photocatalytic Water Purification.

Nowadays, the development of new effective photocatalytic materials for the purification of real wastewaters and model systems containing organic molecules constitutes an important challenge. Here we present a preparation strategy for composite materials based on hexamolybdenum cluster complexes and exfoliated hexagonal boron nitride (h-BN) nanosheets. Cluster deposition on the nanosheet surface was achieved by impregnation of the matrix by a (BuN)[{MoI}(NO)]/acetone solution.

From Specific γ-CD/[Nb Cl (H O) ] Recognition to Biological Activity Tuning.

Specific molecular recognition of γ-cyclodextrin (γ-CD) by the cationic hexanuclear niobium [Nb Cl (H O) ] cluster complex in aqueous solutions results in a 1:1 supramolecular assembly {[Nb Cl (H O) ]@γ-CD} . NMR spectroscopy, isothermal titration calorimetry (ITC), and ESI-MS were used to study the interaction between the inorganic cluster and the organic macrocycle. Such molecular association affects the biological activity of [Nb Cl (H O) ] , decreasing its cytotoxicity despite enhanced cellular uptake.

Size-Exclusion Mechanism Driving Host-Guest Interactions between Octahedral Rhenium Clusters and Cyclodextrins.

In aqueous solution, cyclodextrins (CDs) are able to bind strongly either hydrophobic species or also hydrophilic molecules such as octahedral hexametallic cluster. Systematic investigation of the reactivity between native CDs (α- or β-CD) and water-soluble rhenium clusters [ReQ(CN)] with Q = S, Se, and Te were performed, leading to six new crystal structures revealing different types of supramolecular arrangements. Encapsulation of [ReQ(CN)] (Q = S, Se, or Te) within two β-CDs is observed regardless of the cluster size.

Tuning the chaotropic effect as an assembly motif through one-electron transfer in a rhenium cluster.

We report how only one electron transfer from the hydrophilic reduced cluster [{ReSe}(CN)] induces both a dramatic increase of the host-guest affinity with γ-cyclodextrin and a drastic alteration of the supramolecular dynamics. This striking behaviour, underlined by its thermochemical fingerprint, indicates that the self-assembly process is driven by a chaotropic effect.

Host-Guest Binding Hierarchy within Redox- and Luminescence-Responsive Supramolecular Self-Assembly Based on Chalcogenide Clusters and γ-Cyclodextrin.

Water-soluble salts of anionic [Re Q (CN) ] (Q=S, Se, Te) chalcogenide octahedral rhenium clusters react with γ-cyclodextrin (γ-CD) producing a new type of inclusion compounds. Crystal structures determined through single-crystal X-ray diffraction analysis revealed supramolecular host-guest assemblies resulting from close encapsulations of the octahedral cluster within two γ-CDs. Interestingly, nature of the inner Q ligands influences strongly the host-guest conformation.

Singlet Oxygen Production and Biological Activity of Hexanuclear Chalcocyanide Rhenium Cluster Complexes [{ReQ}(CN)] (Q = S, Se, Te).

Octahedral rhenium cluster complexes have recently emerged as relevant building blocks for the design of singlet oxygen photosensitizing materials toward biological applications such as blue-light photodynamic therapy. However, their singlet oxygen generation ability as well as biological properties have been studied only superficially. Herein we investigate in detail the singlet oxygen photogeneration, dark and photoinduced cytotoxicity, cellular uptake kinetics, cellular localization and in vitro photoinduced oxidative stress, and photodynamic cytotoxicity of the series of octahedral rhenium cluster complexes [{ReQ}(CN)], where Q = S, Se, Te.

A comparative study of hydrophilic phosphine hexanuclear rhenium cluster complexes' toxicity.

The octahedral rhenium cluster compound NaH[{ReSe}(P(CHCONH)(CHCOO))] has recently emerged as a very promising X-ray contrast agent for biomedical applications. However, the synthesis of this compound is rather challenging due to the difficulty in controlling the hydrolysis of the initial P(CHCN) ligand during the reaction process. Therefore, in this report we compare the and toxicity of NaH[{ReSe}(P(CHCONH)(CHCOO))] with those of related compounds featuring the fully hydrolysed form of the phosphine ligand, namely NaH[{ReQ}(P(CHCOO))] (Q = S or Se).