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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-Na 2 H 14 [{Re 6 Q 8 }(P(C 2 H 4 COO) 3 ) 6 ] (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). The reaction between the clusters and PEG-400 was carried out in acidic aqueous media and resulted in the binding of up to five carboxylate groups with PEG. The study of cytotoxicity against Hep-2 cells and acute toxicity in mice showed a twofold reduction in toxicity after PEGylation, demonstrating the success of the strategy chosen. Finally, the compound obtained has been used for the visualization of blood vessels of laboratory rats by angiography and computed tomography.

Understanding the processes that occur during the redox transformations of complexes coordinated by redox-active apical ligands is important for the design of electrochemically active compounds with functional properties. In this work, a detailed analysis of the interaction energy and electronic structure was performed for cluster complexes trans -[Re 6 S 8 bipy 4 Cl 2 ] n (n = 2-, 4-, 6-, 8-), which can be obtained by stepwise electrochemical reduction of a neutral cluster trans -[Re 6 S 8 bipy 4 Cl 2 ] in DMSO solution. It was shown that the formation of open-shell paramagnetic ions with S = 1, 2 and 1 is the most energetically favorable for n = 2-, 4- and 6-, respectively.

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 5 (μ 3 -Se) i 4 (μ 4 -Se) i (μ-pz) i 4 }(pzH) t 5 ] 1+/2+ (pzH = pyrazole, i = inner, t = terminal). Individually obtained oxidized (2+) and reduced (1+) forms have very close geometry (proven by single-crystal X-ray diffraction analysis) and are able to reversibly transform into each other, which was confirmed by cyclic voltammetry. Comprehensive characterization of the complexes, both in solid and in solution, confirms the different charge state of molybdenum in clusters (XPS), magnetic properties (EPR), and so on. DFT calculations complement the diverse study of new complexes, expanding the chemistry of molybdenum chalcogenide clusters.

Reactivity of new tetrahedral rhenium cluster complexes with pnictogenide inner ligands μ 3 -As 3- , μ 3 -Sb 3- , and μ 3 -Bi 3- has been investigated in reactions with aqueous H 2 O 2 . It has been found that the oxidation of clusters [{Re 4 As 3 Q}(CN) 12 ] 7- (Q = S or Se) led to the formation of stable clusters with μ 3 -(AsO) 3- ligands. Under the same conditions, the oxidation of [{Re 4 As 2 S 2 }(CN) 12 ] 6- cluster led to substitution of μ 3 -As 3- ligands to μ 3 -O 2- . The resulting cluster [{Re 4 O 2 S 2 }(CN) 12 ] 4- easily undergoes further oxidation, and even at room temperature, a unique {Re 4 } to {Re 3 } rearrangement occurs with the formation of the new triangular cluster [{Re 3 (μ 3 -S)(μ-O) 2 (μ-SO 2 )}(CN) 9 ] 5- . Upon heating, this process proceeds faster and the triangular cluster can be isolated as individual compounds. Cluster anions [{Re 4 SbSe 3 }(CN) 12 ] 5- and [{Re 4 BiS 3 }(CN) 12 ] 5- reacted with H 2 O 2 , yielding clusters containing μ 3 -O 2- ligands, namely, [{Re 4 OSe 3 }(CN) 12 ] 4- and [{Re 4 OS 3 }(CN) 12 ] 4- . This indicates that oxidized forms of μ 3 -Sb 3- and μ 3 -Bi 3- ligands can be easily substituted.

A series of eight new octahedral rhenium cluster complexes with the general formula trans -[{Re 6 Q 8 }L 4 X 2 ] (Q = S or Se; L = 1,2-Bis(4-pyridyl)ethylene (bpe) or 1,3-Bis(4-pyridyl)propane (bpp); X = Cl or Br) was synthesized and investigated. While bpe is a ligand with a conjugated aromatic system, bpp represents a molecule of opposite type and has independent aromatic systems of the two pyridine rings. It was shown that this difference in the electronic structure of the ligands has a fundamental effect on the electronic structure, electrochemical and luminescent properties of the corresponding cluster complexes. Specifically, the [{Re 6 Q 8 }(bpe) 4 X 2 ] complexes in solutions show multiple quasi-reversible electrochemical transitions associated with reduction of the organic ligands. At the same time, the trans -[{Re 6 Q 8 }(bpp) 4 X 2 ] complexes show multielectron quasi-irreversible reduction processes, which correlate with the mixed character of the lowest unoccupied molecular orbitals of these complexes. All the obtained new compounds exhibit red photoluminescence. The photophysical parameters (emission lifetimes and quantum yields) measured for the bpp complexes exceed those revealed for bpe complexes by more than an order of magnitude.

A series of six coordination polymers based on octahedral cluster anions [Re 6 Q 8 (CN) 6 ] 4- (Q = S or Se) and Ag + cations coordinated by bipyridine analogs were synthesized under solvothermal conditions. Their structures have been characterized by single crystal X-ray diffraction. Compounds 1 and 2 described by the general formula [{Ag(phen)} 4 Re 6 Q 8 (CN) 6 ] (Q = Se ( 1 ), S ( 2 ); phen = 1,10-phenanthroline) exhibit layered structures assembled into a supramolecular network by CH…π contacts. At the same time, compounds [{Ag(bipym)} 2 Ag 2 Re 6 Se 8 (CN) 6 ] (bipym = 2,2'-bipyrimidine) ( 3 ), [{Ag 2 (bipy)}Ag 2 Re 6 Se 8 (CN) 6 ]·CH 3 CN (bipy = 4,4'-bipyridine) ( 4 ) and [{Ag(dpbp)} 4 Re 6 Q 8 (CN) 6 ]·2H 2 O·2CH 3 CN (Q = Se ( 5 ), S ( 6 ); dpbp = 4,4'-Di(4-pyridyl)biphenyl)) evince framework structures. In 1 , 2 , 5 and 6 weak Ag⋯Ag interactions are observed. All the compounds show luminescence in the red region. The luminescence quantum yields and lifetimes were found to be notably higher than those for most of the coordination polymers based on the octahedral rhenium cluster complexes.

Azide cluster complexes [{Re 3 (μ-Br) 3 }(N 3 ) 9 ] 3- and [{Re 3 ( μ -I) 3 }(N 3 ) 9 ] 3- were obtained by reaction of Re 3 X 9 (X = Br or I, respectively) with sodium azide in methanol. The complexes were crystallized as cesium salts of the compositions Cs 3 [{Re 3 (μ-Br) 3 }(N 3 ) 9 ]·H 2 O ( 1 ) and Cs 3 [{Re 3 (μ-I) 3 }(N 3 ) 9 ]·H 2 O ( 2 ) and characterized by X-ray single-crystal diffraction and elemental analyses, mass spectrometry, 14 N NMR spectroscopy, and DFT calculations. In the anions, each rhenium atom is coordinated by three azide ligands. To the best of our knowledge, these compounds represent the first case of metal cluster polyazide complexes (i.e., where each metal atom bears more than one azide ligand). Both complexes are stable in air but are very shock sensitive, and spontaneous explosive decomposition is also possible.

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 W 6 Q 8 -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 W 6 Q 8 L 6 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 6 -clusters on cell viability. The results obtained clearly demonstrate their very low cytotoxicity, comparable to the least-toxic clusters presented in the literature.

Despite the wide variety of strategies developed to combat pathogenic microorganisms, the infectious diseases they cause remain a worldwide health issue. Hence, the search for new disinfectants, which prevent infection spread, constitutes an extremely urgent task. One of the most promising methods is the use of photoactive compounds - photosensitizers, capable of generating reactive oxygen species, in particular, singlet oxygen (O2(1Δg)), which causes rapid and effective death of microorganisms of all types. In this work, we propose the utilization of the powdered cluster complex (Bu4N)2[{Mo6I8}(OTs)6] as a photoactive additive to commercially available fluoroplastic lacquer F-32L to create heterogeneous self-sterilizing coatings. We show that soaking of the prepared films in water for 60 days did not lead to a decrease in their photosensitization properties indicating their excellent stability. Moreover, the use of the cluster complex in the solid state allowed significant expansion of the operating wavelength range, which covers the UV region and a large part of the visible region (250-650 nm). The films displayed high photoantimicrobial activity against five common pathogens (bacteria and fungi) under white-light irradiation. Overall, the properties demonstrated make these materials promising for practical use in everyday outdoor and indoor disinfection since they are active under both sunlight and artificial lighting.

The energy and structural parameters were obtained for all forms of the carbonyl complex of osmium Os 3 (CO) 12 with D 3h and D 3 symmetries using density functional theory (DFT) methods. The calculations took into account various levels of relativistic effects, including those associated with nonconservation of spatial parity. It was shown that the ground state of Os 3 (CO) 12 corresponds to the D 3 symmetry and thus may be characterized either as left-twisted (D 3S ) or right-twisted (D 3R ). The D 3S ↔D 3R transitions occur through the D 3h transition state with an activation barrier of ~10 -14 kJ/mol. Parity violation energy difference (PVED) between D 3S and D 3R states equals to ~5 × 10 -10 kJ/mol. An unusual three-center exchange interaction was found inside the {Os 3 } fragment. It was found that the cooperative effects of the mutual influence of osmium atoms suppress the chirality of the electron system in the cluster.

The reaction of the K 4 [{Re 6 S i 8 }(OH) a 6 ]·8H 2 O rhenium cluster salt with pyrazine (Pz) in aqueous solutions of alkaline or alkaline earth salts at 4 °C or at room temperature leads to apical ligand exchange and to the formation of five new compounds: [ trans- {Re 6 S i 8 }(Pz) a 2 (OH) a 2 (H 2 O) a 2 ] ( 1 ), [ cis- {Re 6 S i 8 }(Pz) a 2 (OH) a 2 (H 2 O) a 2 ] ( 2 ), (NO 3 )[ cis- {Re 6 S i 8 }(Pz) a 2 (OH) a (H 2 O) a 3 ](Pz)·3H 2 O ( 3 ), [Mg(H 2 O) 6 ] 0.5 [ cis- {Re 6 S i 8 }(Pz) a 2 (OH) a 3 (H 2 O) a ]·8.5H 2 O ( 4 ), and K[ cis -{Re 6 S i 8 }(Pz) a 2 (OH) a 3 (H 2 O) a ]·8H 2 O ( 5 ). Their crystal structures are built up from trans - or cis -[{Re 6 S i 8 }(Pz) a 2 (OH) a 4-x (H 2 O) a x ] x-2 cluster units. The cohesions of the 3D supramolecular frameworks are based on stacking and H bonding, as well as on H 3 O 2- bridges in the cases of ( 1 ), ( 2 ), ( 4 ), and ( 5 ) compounds, while ( 3 ) is built from stacking and H bonding only. This evidences that the nature of the synthons governing the cluster unit assembly is dependent on the hydration rate of the unit.

The interaction of rhenium(III) halides Re 3 Br 9 and Re 3 I 9 with aqueous solution of sodium cyanide resulted in the formation of the first trinuclear halide-cyanide rhenium cluster complexes [{Re 3 X 3 }(CN) 9 ] 5- /[{Re 3 X 3 }(CN) 9 ] 4- (X = Br or I) crystallized as salts of the compositions Cs 4 Na[{Re 3 Br 3 }(CN) 9 ]·5.25H 2 O ( 1 ), Cs 4 Na[{Re 3 I 3 }(CN) 9 ]·6H 2 O ( 2 ), Cs 4 [{Re 3 Br 3 }(CN) 9 ]·2H 2 O·0.5CsCl ( 3 ), and Cs 4 [{Re 3 I 3 }(CN) 9 ]·( 4 ). All of the compounds are stable in air in the solid state and in aqueous solution. The substitution of apical halide ligands in the parent compounds Re 3 X 9 by cyanides led to reduction of the original metallocluster Re 3 9+ (12 cluster valence electrons (CVEs)) to Re 3 7+ (14 CVEs), forming the compounds 1 and 2 . The apical CN - ligands affect the electronic structure of the Re 3 metallocluster stabilizing reduced form. Complexes 1 and 2 represent the first examples of triangular rhenium clusters with the Re 3 7+ metallocluster. The reaction of 1 and 2 with H 2 O 2 resulted in formation of compounds 3 and 4 with the formal charge of the Re 3 metallocluster equal to 8+, and no further oxidation to Re 3 9+ occurred. The compounds were characterized by the X-ray diffraction analysis, NMR and UV-vis spectroscopies, mass spectrometry, cyclic voltammetry, and magnetic susceptibility measurements.

The reactions of ReI 3 , Se, and KCN with Sb 2 O 3 or Bi 2 O 3 at elevated temperature led to the formation of two new tetrahedral clusters with mixed-ligand cluster cores {Re 4 Se 3 Sb} 7+ and {Re 4 Se 3 Bi} 7+ . They are the first examples of complexes with either Sb 3- or Bi 3- ligands, which have never been previously described in the literature.

Compounds based on new cyanide cluster anions [{Mo 6 I 8 }(CN) 6 ] 2- , trans -[{Mo 6 I 8 }(CN) 4 (MeO) 2 ] 2- and trans -[{W 6 I 8 }(CN) 2 (MeO) 4 ] 2- were synthesized using mechanochemical or solvothermal synthesis. The crystal and electronic structures as well as spectroscopic properties of the anions were investigated. It was found that the new compounds exhibit red luminescence upon excitation by UV light in the solid state and solutions, as other cluster complexes based on {Mo 6 I 8 } 4+ and {W 6 I 8 } 4+ cores do. The compounds can be recrystallized from aqueous methanol solutions; besides this, it was shown using NMR and UV-Vis spectroscopy that anions did not undergo hydrolysis in the solutions for a long time. These facts indicate that hydrolytic stabilization of {Mo 6 I 8 } and {W 6 I 8 } cluster cores can be achieved by coordination of cyanide ligands.

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 [P 2 W 18 O 62 ] 6- and electron-rich rhenium clusters. It is worth noting that a cluster-based cation [{Re 6 Se 8 }(H 2 O) 6 ] 2+ on one hand and a cluster-based anion on the other hand [{Re 6 Se 8 }(CN) 6 ] 4- can be associated with the anionic POM. In the absence of the supramolecular connector, a "CLUSPOM salt" was obtained from aqueous solution of the cationic cluster and the polyoxometalate. In this solid, the arrangement between the polymetallic building blocks is mainly governed by long-range Coulombic interactions. In the presence of γ-CD, the Dawson anion and the cationic cluster are assembled differently, forming a hierarchical supramolecular solid, K 2 [{Re 6 Se 8 }(H 2 O) 6 ] 2 {[P 2 W 18 O 62 ]@2γ-CD}·42H 2 O, where the organic macrocycle acts as a ditopic linker between the inorganic building blocks. In such an edifice, the short-range molecular recognition dominates the long-range Coulombic interactions leading to a specific three-dimensional organization. Interestingly, the assembling of anionic POM [P 2 W 18 O 62 ] 6- with the anionic rhenium cluster [{Re 6 Se 8 }(CN) 6 ] 4- is also achieved with γ-CD despite the repulsive forces between the nanosized anions. The resulting solid, K 10 {[{Re 6 Se 8 }(CN) 6 ]@2γ-CD}[P 2 W 18 O 62 ]·33H 2 O, is built from 1:2 inclusion complexes {[{Re 6 Se 8 }(CN) 6 ]@2γ-CD} 4- linked by a POM unit interacting with the exterior wall of the organic macrocycle. Multinuclear NMR and small-angle X-ray scattering investigations support supramolecular preorganization in aqueous solution prior to crystallization.

A reaction between ReI 3 and KCN at elevated temperature led to the formation of the new cyanometalate cluster anion [{Re 4 (μ 3 -CCN) 4 }(CN) 12 ] 8- ( 1 ). The anion contains μ 3 -CCN 3- ligands, which are stabilized by the coordination to the triangular faces of the tetrahedral {Re 4 } metallocluster in a μ 3 mode. The compound crystallized as a potassium salt, and its crystal structure was determined by single-crystal X-ray diffraction analysis. It was shown that μ 3 -CCN 3- ligands are ambidentate and can interact with transition-metal cations similarly to terminal CN groups, resulting in the polymer framework formation.

The light-induced antibacterial and antifungal properties of A 2 [M 6 I 8 L 6 ] with M = Mo and W, A = organic cation, L = ligand have been studied. The photoactive compounds (TBA) 2 [W 6 I 8 (C 7 H 7 SO 3 ) 6 ] and (TBA) 2 [W 6 I 8 (COOCF 3 ) 6 ] have been incorporated into a permeable silicone matrix and were measured for their application in the decomposition of multi-resistant bioactive species (hospital germs) such as S. aureus and P. aeruginosa as well as fungi. In addition, we present a new high volume synthesis route for these types of cluster compounds departing from the soluble compound W 6 I 22 ., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Substitution of terminal halide ligands of octahedral rhenium cluster complexes [Re 6 Q 8 X 6 ] 4- in a melt of 4,4'-bipyridine (bpy) led to us obtaining four new compounds with the general formula trans -[Re 6 Q 8 (bpy) 4 X 2 ] (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 1 - 4 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. In particular, it was shown that compounds 1 - 4 in the DMSO solution exhibit four reversible reduction processes. A comparison of the obtained data with the results of DFT calculations of the electronic structure suggests that these processes correspond to two-electron reduction of all four bpy ligands. The reduction potentials are shifted to the positive region compared with the potential of free bipyridine, and the value of the shift depends on the composition of the cluster core. The presence of four transitions also suggests that electronic exchange between terminal ligands in the cis -position is possible. The study of the luminescence of the compounds showed that emission maxima of selenide clusters almost coincide with those of sulfide ones, while luminescence spectra of the complexes with chloride terminal ligands ( 1 and 3 ) are slightly blue-shifted relative to the spectra of the complexes with bromide ligands ( 2 and 4 ).

New octahedral rhenium cluster complexes [{Re 6 Q 8 }(SO 3 ) 6 ] 10- (Q = S or Se) were synthesized starting from [{Re 6 Q 8 }(H 2 O) 4 (OH) 2 ]·12H 2 O. The complexes were crystallized as sodium salts and characterized by X-ray single-crystal diffraction and elemental analyses, IR, UV/vis and luminescence spectroscopies. Magnetic relaxation data demonstrate the complex formation of the cluster units with gadolinium ions. The analysis of the magnetic relaxation rates measured at various Gd:cluster ratios and different concentrations revealed the conversion of the aggregates (Gd x [{Re 6 Se 8 }(SO 3 ) 6 ] y ) n - into a nanoparticulate form even at x = 1 and y ≥ 1. Thus, the self-assembly of the cluster units into the nanoparticles is greatly facilitated by counterion binding with sodium cations. The concentration conditions were optimized for the formation and hydrophilization of Na x Gd y [{Re 6 Q 8 }(SO 3 ) 6 ]-based colloids with the magnetic relaxivity values of r 1(2) = 21.0(24.1) and r 1(2) = 25.9(29.8) mM -1 s -1 for the {Re 6 S 8 } 2+ and {Re 6 Se 8 } 2+ derivatives, respectively.

Finding methods that fight bacterial infection or contamination, while minimising our reliance on antibiotics is one of the most pressing needs of this century. Although the utilisation of UV-C light and strong oxidising agents, such as bleach, are still efficacious methods for eliminating bacterial surface contamination, both methods present severe health and/or environmental hazards. Materials with intrinsic photodynamic activity (i.e. a material's ability upon photoexcitation to convert molecular oxygen into reactive oxygen species such as singlet oxygen), which work with light within the visible photomagnetic spectrum could offer a significantly safer alternative. Here we present a new, bespoke molybdenum cluster (Bu 4 N) 2 [{Mo 6 I 8 }(CF 3 (CF 2 ) 6 COO) 6 ], which is both efficient in the generation of singlet oxygen upon photoirradiation and compatible with the fluoropolymer (F-32L) known for its good oxygen permeability. Thus, (Bu 4 N) 2 [{Mo 6 I 8 } (CF 3 (CF 2 ) 6 COO) 6 ]/F-32L mixtures have been solution-processed to give homogenous films of smooth and fibrous morphologies and which displayed high photoinduced antibacterial activity against four common pathogens under visible light irradiation. These materials thus have potential in applications ranging from antibacterial coatings to filtration membranes and air conditioners to prevent spread of bacterial infections., (Copyright © 2019 Elsevier B.V. All rights reserved.)

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 [Re 6 Q 8 (CN) 6 ] 4- with Q = S, Se, and Te were performed, leading to six new crystal structures revealing different types of supramolecular arrangements. Encapsulation of [Re 6 Q 8 (CN) 6 ] 4- (Q = S, Se, or Te) within two β-CDs is observed regardless of the cluster size. Interestingly, different assembling scenarios are pointed out depending on the host-guest matching featured by no, partial, or deep inclusion complexes that involved either primary or secondary rim of the CD tori. In the specific case of α-CD, only the smaller cluster [Re 6 S 8 (CN) 6 ] 4- is able to form inclusion complex with the tori host. Solution investigations, using a set of complementary techniques including isothermal titration calorimetry, multinuclear NMR methods, cyclic voltammetry, and electrospray ionization mass spectrometry, corroborate nicely conclusions of the solid-state studies. It appears clearly that size-matching supported by solvent effects play key roles in the stability of the host-guest complexes. At last, circular dichroism studies underline that the chirality induction from cyclodextrins to the rhenium cluster depends strongly on the strength of host-guest interactions.

The first luminescent twelve-nuclear rhenium cluster complexes were obtained. Three new clusters, namely, [Re 12 CS 14 (μ-Cl) 3 Cl 6 ] 5- , [Re 12 CS 14 (μ-Br) 3 Cl 6 ] 5- and [Re 12 CS 14 (μ-Br) 3 Br 6 ] 5- , were synthesized using the non-isovalent substitution of μ-O ligands within the {Re 12 CS 14 (μ-O) 3 } 0 cluster core by halide anions. The geometry of the new clusters was investigated by X-ray structural analysis, and the electronic structures were evaluated by the use of DFT calculations. It was found that compounds based on these anions showed red luminescence in both the solid state and solution that was never observed before for previously studied twelve-nuclear rhenium clusters.

We report how only one electron transfer from the hydrophilic reduced cluster [{Re 6 Se 8 }(CN) 6 ] 4- 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.

New tetrahedral anionic rhenium cluster complexes [{Re 4 (PO) 3 (PO 2 )}(CN) 12 ] 8- (1) and [{Re 4 As 2 (AsO) 2 }(CN) 12 ] 8- (2) have been synthesized by the reaction of ReI 3 with NaCN and P red or KCN and As gray , respectively. Compound 2 was further oxidized by aqueous H 2 O 2 to produce the cluster anion [{Re 4 (AsO) 4 }(CN) 12 ] 8- (3). The anions contain new pnictogen/oxygen-based ligands, PO 2 3- and AsO 3- , which were stabilized by the coordination to the triangular faces of the tetrahedral Re 4 metallocluster in μ 3 -mode. All three compounds were crystallized as either sodium or potassium salts, and their crystal structures were determined by single crystal X-ray diffraction analysis.

Unlike silica nanoparticles, the potential of silica mesoparticles (SMPs) (i.e. particles of submicron size) for biological applications in particular the in vitro (let alone in vivo) cellular delivery of biological cargo has so far not been sufficiently studied. Here we examine the potential of luminescent (namely, octahedral molybdenum cluster doped) SMPs synthesised by a simple one-pot reaction for the labelling of cells and for protein transduction into larynx carcinoma (Hep-2) cells using GFP as a model protein. Our data demonstrates that the SMPs internalise into the cells within half an hour. This results in cells that detectably luminesce via conventional methods. In addition, the particles are non-toxic both in darkness and upon photo-irradiation. The SMPs were modified to allow their functionalisation by a protein, which then delivered the protein (GFP) efficiently into the cells. Thus, the luminescent SMPs offer a cheap and trackable alternative to existing materials for cellular internalisation of proteins, such as the HIV TAT protein and commercial protein delivery agents (e.g. Pierce™)., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Tungsten trioxide has been found to be a convenient precursor for the synthesis of metal cluster compounds with new types of cluster cores. The reaction between WO3 and KCN led to the formation of the cluster complex [{W6(μ4-O)2(μ3-CCN)4}(CN)16]10-. Unexpectedly, it includes the fully deprotonated form of acetonitrile, the CCN3- anion, as a μ3-bridging ligand coordinated to the trigonal faces of the bitetrahedral W6 metallocluster. A similar complex [{W6(μ4-O)2(μ3-As)4}(CN)16]10- containing μ3-As3- ligands instead of μ3-CCN3- ones has been synthesized by the reaction between WO3, As and KCN.

Octahedral molybdenum and tungsten clusters have potential biological applications in photodynamic therapy and bioimaging. However, poor solubility and hydrolysis stability of these compounds hinder their application. The first water-soluble photoluminescent octahedral tungsten cluster [{W 6 I 8 }(DMSO) 6 ](NO 3 ) 4 was synthesised and demonstrated to be at least one order of magnitude more stable towards hydrolysis than its molybdenum analogue. Biological studies of the compound on larynx carcinoma cells suggest that it has a significant photoinduced toxicity, while the dark toxicity increases with the increase of the degree of hydrolysis. The increase of the dark toxicity is associated with the in situ generation of nanoparticles that clog up the cisternae of rough endoplasmic reticulum., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Water-soluble salts of anionic [Re 6 Q 8 (CN) 6 ] 4- (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. The cluster [Re 6 S 8 (CN) 6 ] 4- interacts preferentially with the primary faces of the γ-CD while the bulkier clusters [Re 6 Se 8 (CN) 6 ] 4- and [Re 6 Te 8 (CN) 6 ] 4- exhibit specific interactions with the secondary faces of the cyclic host. Furthermore, analysis of the crystal packing reveals additional supramolecular interactions that lead to 2D infinite arrangements with [Re 6 S 8 (CN) 6 ] 4- or to 1D "bamboo-like" columns with [Re 6 Se 8 (CN) 6 ] 4- and [Re 6 Te 8 (CN) 6 ] 4- species. Solution studies, using multinuclear NMR methods, ESI-MS and Isothermal titration calorimetry (ITC) corroborates nicely the solid-state investigations showing that supramolecular pre-organization is retained in aqueous solution even in diluted conditions. Furthermore, ITC analysis showed that host-guest stability increases significantly ongoing from S to Te. At last, we report herein that deep inclusion alters significantly the intrinsic physical-chemical properties of the octahedral clusters, allowing redox tuning and near IR luminescence enhancement., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The redox-active rhenium octahedral cluster unit [Re 6 Se 8 (CN) 6 ] 4- was combined with Gd 3+ ions and dicarboxylate linkers in novel types of metal-organic frameworks (MOFs) that display a set of functional properties. The hydrolytically stable complexes [{Gd(H 2 O) 3 } 2 (L)Re 6 Se 8 (CN) 6 ]·nH 2 O (1, L = furan-2,5-dicarboxylate, fdc; 2, L = thiophene-2,5-dicarboxylate, tdc) exhibit a 3D framework of trigonal symmetry where 1D chains of [{Gd(H 2 O) 3 } 2 (L)] 4+ are connected by [Re 6 Se 8 (CN) 6 ] 4- clusters. Frameworks contain spacious channels filled with H 2 O. Solvent molecules can be easily removed under vacuum to produce permanently porous solids with high volumetric CO 2 uptake and remarkable CO 2 /N 2 selectivity at room temperature. The frameworks demonstrate an ability for reversible redox transformations of the cluster fragment. The orange powders of compounds 1 and 2 react with Br 2 , yielding dark-green powders of [{Gd(H 2 O) 3 } 2 (L)Re 6 Se 8 (CN) 6 ]Br·nH 2 O (3, L = fdc; 4, L = tdc). Compounds 3 and 4 are isostructural with 1 and 2 and also have permanently porous frameworks but display different optical, magnetic, and sorption properties. In particular, oxidation of the cluster fragment "switches off" its luminescence in the red region, and the incorporation of Br - leads to a decrease of the solvent-accessible volume in the channels of 3 and 4. Finally, the green powders of 3 and 4 can be reduced back to the orange powders of 1 and 2 by reaction with hydrazine, thus displaying a rare ability for fully reversible chemical redox transitions. Compounds 1-4 are mentioned as a new class of redox-active cluster-based MOFs with potential usage as multifunctional materials for gas separation and chemical contamination sensors.

Photoactive transition metal compounds that are prone to reversible redox reactions are important for myriad applications, including catalysis, optoelectronics, and sensing. This article describes chemical and electrochemical methods to prepare cluster complex (Bu 4 N)[{Mo 6 I 8 }Cl 6 ], a rare example of a 23 e - cluster complex within the family of octahedral clusters of Mo, W, and Re. The low temperature and room temperature crystal structures; electronic structure; and the magnetic, optical, and electrochemical properties of this complex are described.

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 [{Re 6 Q 8 }(CN) 6 ] 4- , where Q = S, Se, Te. Our results demonstrate that the selenium-containing complex possesses optimal properties in terms of absorption and singlet oxygen productivity. These features coupled with the cellular internalization and low dark toxicity lead to the first photoinduced cytotoxic effect observed for a molecular [{M 6 Q 8 }L 6 ] complex, making it a promising object for further study in terms of blue-light PDT.

Selective substitution of μ-SO 2 2- groups by either O 2- or Se 2- ions occurs upon heating the bioctahedral rhenium cluster complex K 6 [Re 12 CS 14 (μ-SO 2 ) 3 (CN) 6 ] in air atmosphere or in the presence of a Se source, respectively, manifesting the remarkable lability of SO 2 2- ligands bound to a transition-metal cluster. A series of compounds based on the new mixed-ligand anions, [Re 12 CS 14 (μ-O) 3 (CN) 6 ] 6- , [Re 12 CS 14 (μ-Se) 3 (CN) 6 ] 6- , and [Re 12 CS 14 (μ-O) 3 (OH) 6 ] 6- , were isolated and their solid-state structures were elucidated by single-crystal X-ray diffraction analysis. Along with the previously reported μ-sulfide clusters, the new species constitute a series of rhenium anionic complexes with the common formula [Re 12 CS 14 (μ-Q) 3 L 6 ] 6- (Q = O, S, Se, L = CN - ; Q = O, S, L = OH - ), within which the total charge and number of cluster valence electrons (CVEs) are constant. The article presents insights into the mechanistic and synthetic aspects of the substitution process, and it comprehensively discusses the influence of inner ligand environment on the structure, spectroscopic characteristics, and electrochemical behavior of the novel compounds.

Octahedral metal cluster complexes have high potential for biomedical applications. In order to evaluate the benefits of these moieties for combined CT/X-ray luminescence computed tomography, this paper compares photoluminescence, radiodensity and X-ray induced luminescence properties of eight related octahedral molybdenum and tungsten cluster complexes [{M 6 I 8 }L 6 ] n (where M is Mo or W and L is I - , NO 3 - , OTs - or OH - /H 2 O). This article demonstrates that despite the fact that molybdenum cluster complexes are better photoluminescence emitters, tungsten cluster complexes, in particular (Bu 4 N) 2 [{W 6 I 8 }I 6 ], demonstrate significantly higher X-ray induced luminescence due to a combination of relatively good photoluminescence properties and high X-ray attenuation. Additionally, photo-degradation of [{M 6 I 8 }(NO 3 ) 6 ] 2- was evaluated.

The octahedral rhenium cluster compound Na 2 H 8 [{Re 6 Se 8 }(P(C 2 H 4 CONH 2 )(C 2 H 4 COO) 2 ) 6 ] 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(C 2 H 4 CN) 3 ligand during the reaction process. Therefore, in this report we compare the in vitro and in vivo toxicity of Na 2 H 8 [{Re 6 Se 8 }(P(C 2 H 4 CONH 2 )(C 2 H 4 COO) 2 ) 6 ] with those of related compounds featuring the fully hydrolysed form of the phosphine ligand, namely Na 2 H 14 [{Re 6 Q 8 }(P(C 2 H 4 COO) 3 ) 6 ] (Q = S or Se). Our results demonstrate that the cytotoxicity and acute in vivo toxicity of the complex Na 2 H 8 [{Re 6 Se 8 }(P(C 2 H 4 CONH 2 )(C 2 H 4 COO) 2 ) 6 ] solutions were considerably lower than those of compounds with the fully hydrolysed ligand P(C 2 H 4 COOH) 3 . Such behavior can be explained by the higher osmolality of Na 2 H 14 [{Re 6 Q 8 }(P(C 2 H 4 COO) 3 ) 6 ] versus Na 2 H 8 [{Re 6 Se 8 }(P(C 2 H 4 CONH 2 )(C 2 H 4 COO) 2 ) 6 ].

Octahedral rhenium cluster complexes may have considerable potential as therapeutic and diagnostic drugs due to their luminescent and X-ray contrast properties, as well as their ability to generate singlet oxygen upon photoirradiation. However, their potential biological effects and toxicity in vitro and in vivo are rather far from being understood. Thus, the aim of our research was to study cytotoxicity, intracellular localization and cellular uptake/elimination kinetics in vitro, biodistribution and acute intravenous toxicity in vivo of a complex Na 4 [{Re 6 Te 8 }(CN) 6 ] as the promising compound for biomedical application. The results have demonstrated that the complex penetrates through cell membranes with the maximum accumulation in cells in 24h of incubation and have low toxic effects in vitro and in vivo. The median lethal dose (LD 50 ) of intravenously administrated Na 4 [{Re 6 Te 8 }(CN) 6 ] is equal to 1082±83mg/kg. These findings will be useful for future development of cluster-based agents for different biomedical applications., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Inclusion compounds of photoluminescent hexamolybdenum cluster complexes in the chromium terephthalate metal-organic framework, MIL-101 (MIL, Matérial Institut Lavoisier) were successfully synthesized in two different ways and characterized by means of powder X-Ray diffraction, chemical analysis and nitrogen sorption. Some important functional properties of hexamolybdenum cluster complexes for biological and medical applications, in particular singlet oxygen generation ability, luminescence properties, cellular uptake behavior and cytotoxicity were studied. It was revealed that the inclusion compounds possessed significant singlet oxygen generation activity. The materials obtained showed a low cytotoxicity, thus allowing them to be used in living cells. Confocal microscopy of human larynx carcinoma (Hep-2) cells incubated with the inclusion compounds showed that MIL-101 performed as a nanocarrier adhering to the external cell membrane surface and releasing the cluster complexes which that penetrated into the cells. Moreover, photoinduced generation of reactive oxygen species (ROS) in Hep-2 cells incubated with inclusion compounds was demonstrated. The cluster supported on MIL-101 was shown to possess in vivo phototoxicity., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The octahedral cluster compound Na 2 H 8 [{Re 6 Se 8 }(P(C 2 H 4 CONH 2 )(C 2 H 4 COO) 2 ) 6 ] has been shown to be highly radio dense, thus becoming a promising X-ray contrast agent. It was also shown that this compound had low cytotoxic effect in vitro, low acute toxicity in vivo and was eliminated rapidly from the body through the urinary tract. The present contribution describes a more detailed cellular internalization assay and morphological analysis after intravenous injection of this hexarhenium cluster compound at different doses. The median lethal dose (LD 50 ) of intravenously administrated compound was calculated (4.67 ± 0.69 g/kg). Results of the study clearly indicated that the cluster complex H n [{Re 6 Se 8 }(P(C 2 H 4 CONH 2 )(C 2 H 4 COO) 2 ) 6 ] n-10 was not internalized into cells in vitro and induced only moderate morphological alterations of kidneys at high doses without any changes in morphology of liver, spleen, duodenum, or heart of mice. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)

This article describes the synthesis, structures and systematic study of the spectroscopic and redox properties of a series of octahedral molybdenum metal cluster complexes with aromatic sulfonate ligands ( n Bu 4 N) 2 [{Mo 6 X 8 }(OTs) 6 ] and ( n Bu 4 N) 2 [{Mo 6 X 8 }(PhSO 3 ) 6 ] (where X - is Cl - , Br - or I - ; OTs - is p-toluenesulfonate and PhSO 3 - is benzenesulfonate). All the complexes demonstrated photoluminescence in the red region and an ability to generate singlet oxygen. Notably, the highest quantum yields (>0.6) and narrowest emission bands were found for complexes with a {Mo 6 I 8 } 4+ cluster core. Moreover, cyclic voltammetric studies revealed that ( n Bu 4 N) 2 [{Mo 6 X 8 }(OTs) 6 ] and ( n Bu 4 N) 2 [{Mo 6 X 8 }(PhSO 3 ) 6 ] confer enhanced stability towards electrochemical oxidation relative to corresponding starting complexes ( n Bu 4 N) 2 [{Mo 6 X 8 }X 6 ].

Silica nanoparticles (SNPs) doped by hexanuclear molybdenum cluster complexes [{Mo 6 X 8 }L 6 ] n (X = Cl, Br, or I; L = various inorganic or organic ligands) have been recently suggested as materials with high potential for biomedical applications due to both their outstanding photoluminescence properties and their ability to efficiently generate singlet oxygen upon photoirradiation. However, no studies were undertaken so far to prove this concept. Therefore, here we examined the potential of photoluminescent SNPs doped by {Mo 6 I 8 } 4+ for applications such as bioimaging and photodynamic therapy using the human epidermoid larynx carcinoma (Hep-2) cell line as a model. Our results demonstrated both: (i) significant luminescence from cells with internalised molybdenum cluster-doped SNPs combined with the low cytotoxicity of particles in the darkness and (ii) significant cytotoxicity of the particles upon photoirradiation. Thus, this research provides strong experimental evidence for high potential of molybdenum-cluster-doped materials in biomedical applications such as optical bioimaging, biolabeling and photodynamic therapy.

The present work describes a new method to sense cholinesterase-catalyzed hydrolysis of acetylcholine (ACh) through a luminescence response of the hexarhenium cluster complex [{Re6S8}(OH)6](4-). A proton released from acetylcholinesterase (AChE)- or butyrylcholinesterase (BuChE)-catalyzed hydrolysis of ACh results in time-resolved sensitization of cluster-centered luminescence. The sensitization results from protonation of apical hydroxo-groups of the cluster complex. The protonation is affected by a counter ion effect. Thus, optimal conditions for adequate sensing of acetic acid produced by ACh hydrolysis are highlighted. Time-resolved luminescence and pH measurements under conditions of AChE-catalyzed hydrolysis of ACh show a good correlation between the cluster-centered luminescence and pH-induced inhibition of AChE. The inhibition is not significant within the first two minutes of ACh hydrolysis. Thus, the luminescence response measured within two minutes is dependent on both substrate and enzyme concentrations, which fits with AChE and BuChE kinetics. The usability of cluster-centered luminescence for monitoring the concentration-dependent inhibition of AChE with irreversible inhibitors is demonstrated, using a carbamylating agent, pyridostigmine bromide, as a model.

Although many of the layered metal chalcogenides, such as MoS2, are well-studied, some other chalcogenides have received less attention by comparison. In particular, there has been an emerging interest in vanadium tetrasulfide (VS4), which displays useful properties as a component of hybrids. However, the synthetic methods and characteristics of individual VS4 are not yet well defined, and there is no report on its solution processability. Here we have synthesized VS4 by a simple and fast direct reaction between elements. Reinvestigation of the VS4 crystal structure yielded more precise atomic coordinates and interatomic distances, thereby confirming the crystallization of VS4 in the monoclinic C2/c group and its quasi-1D chainlike structure. As the chains in VS4 are only bonded by weak van der Waals forces, we further demonstrate that bulk VS4 may be ultrasonically dispersed in appropriate solvents to form colloids, similarly to the layered chalcogenides. VS4 particles in colloids retain their phase identity and rod-shaped morphology with lengths in the range of hundreds of nanometers. Isopropanol dispersion exhibited the highest concentration and stability, which was achieved owing to the repulsion caused by high negative charges on the edges of the particles., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Investigation of new X-ray contrast media for radiography is an important field of science since discovering of X-rays in 1895. Despite the wide diversity of available X-ray contrast media the toxicity, especially nephrotoxicity, is still a big problem to be solved. The octahedral metal-cluster complexes of the general formula [{M6Q8}L6] can be considered as quite promising candidates for the role of new radiocontrast media due to the high local concentration of heavy elements, high tuning ability of ligand environment and low toxicity. To exemplify this, the X-ray computed tomography experiments for the first time were carried out on some octahedral cluster complexes of molybdenum and rhenium. Based on the obtained data it was proposed to investigate the toxicological proprieties of cluster complex Na2H8[{Re6Se8}(P(CH2CH2CONH2)(CH2CH2COO)2)6]. Observed low cytotoxic and acute toxic effects along with rapid renal excretion of the cluster complex evidence its perspective as an X-ray contrast media for radiography., (Copyright © 2014 Elsevier Inc. All rights reserved.)

The hexarhenium cluster complexes with benzotriazolate apical ligands [{Re6(μ3-Q)8}(BTA)6](4-) (Q = S, Se; BTA = benzotriazolate ion) were obtained by the reaction of [{Re6(μ3-Q)8}(OH)6](4-) with molten 1H-BTA (1H-benzotriazole). The clusters were crystallized as potassium salts and characterized by X-ray single-crystal diffraction, elemental analyses, and UV-vis and luminescence spectroscopy. In addition, their cellular uptake and toxicity were evaluated. It was found that both clusters exhibited luminescence with high lifetimes and quantum yield values; they were taken up by the cells illuminating them under UV irradiation and, at the same time, did not exhibit acute cytotoxic effects.

The synthesis and characterisation of a new, highly luminescent inorganic cluster complex, (Bu4N)2[Mo6I8(NO3)6], are described. The complex possesses labile nitrato ligands and is therefore a useful precursor for the design of new luminescent materials. To exemplify this, functionalised polystyrene beads have been utilised as "polymeric ligands" to immobilise the molybdenum cluster complex.

We report the direct facile high-temperature synthesis and investigation of heterometallic rhenium-molybdenum cluster K6[Re3Mo3S8(CN)4(CN)2/2] (1) with a new {Re3Mo3S8} core. Dissolution of polymeric compound 1 resulted in subsequent oxidation and formation of stable 23e paramagnetic anionic cluster complex [Re3Mo3S8(CN)6](6-).

We studied the biodistribution of luminescent octahedral rhenium cluster complex K4[Re6S8(CN)6], a promising agent for photodynamic therapy. It was shown that rhenium complex [Re6S8(CN)6](4-)is mainly accumulated in the liver, the central organ of metabolism, and can be excreted by the kidneys. The cluster complex was also accumulated in the spleen in significant amount, which makes it a promising agent for creation of preparations for diagnostics and treatment of lymphoproliferative disorders. The mean lethal dose of the cluster complex was 0.38 g/kg.

An oxidation of cluster anion [Re(12)CS(17)(CN)(6)](6-) by H(2)O(2) in water has been investigated. It was shown that selective two-step oxidation of bridging μ(2)-S-ligands in trigonal prismatic unit {Re(3)(μ(6)-C)(μ(2)-S)(3)Re(3)} takes place. The first stage runs rapidly, whereas the speed of the second stage depends on intensity of ultraviolet irradiation of the reaction mixture. Each stage of the reaction is accompanied by a change in the solution's color. In the first stage of the oxidation, the cluster anion [Re(12)CS(14)(SO(2))(3)(CN)(6)](6-) is produced, in which all bridging S-ligands are turned into bridging SO(2)-ligands. The second stage of the oxidation leads to formation of the anion [Re(12)CS(14)(SO(2))(2)(SO(3))(CN)(6)](6-), in which one of the SO(2)-ligands underwent further oxidation forming the bridging SO(3)-ligand. Seven compounds containing these anions were synthesized and characterized by a set of different methods, elemental analyses, IR and UV/vis spectroscopy, and quantum-chemical calculations. Structures of some compounds based on similar cluster anions, [Cu(NH(3))(5)](3)[Re(12)CS(14)(SO(2))(3)(CN)(6)]·9.5H(2)O, [Ni(NH(3))(6)](3)[Re(12)CS(14)(SO(2))(3)(CN)(6)]·4H(2)O, and [Cu(NH(3))(5)](2.6)[Re(12)CS(14)(SO(2))(3)(CN)(6)](0.6)[{Re(12)CS(14)(SO(2))(2)(SO(3))(CN)(5)(μ-CN)}{Cu(NH(3))(4)}](0.4)·5H(2)O, were investigated by X-ray analysis of single crystals.

The encapsulation of a nanometer-sized octahedral anionic rhenium cluster complex with six terminal hydroxo ligands [Re(6)S(8)(OH)(6)](4-) in maltose-decorated poly(propylene amine) dendrimers (POPAM, generation 4 and 5) has been investigated. Ultrafiltration experiments showed that maximal loading capacity of the dendrimers with the cluster complex is achieved after about ten hours in aqueous solution. To study the inclusion phenomena, three different methods have been applied: UV/Vis, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and laser-induced liquid bead ion desorption mass spectrometry (LILBID-MS). From the results obtained, it could be concluded that: a) the hydrolytic stability of the rhenium cluster complex is significantly enhanced in the presence of dendritic hosts; b) the cluster anions are preferentially bound inside the dendrimers; c) the number of cluster complexes encapsulated in the dendrimers increases with rising dendrimer generation. On average, four to five cluster anions can preferentially be captured in the interior of sugar-coated dendritic carriers. An asymptotic progression of the release of cluster complexes from the loaded dendrimers was observed under physiologically relevant conditions (isotonic sodium chloride solution: approximately 93 % within 4 days for loaded POPAM-G4-maltose; approximately 86 % within 4 days for loaded POPAM-G5-maltose). These encapsulation and release properties of maltose-decorated nanocarriers imply the possibility for the development of the next generation of dendritic nanocarriers with specific targeting of destined tissue for therapeutic treatments.

The embedding of functional inorganic entities into polymer matrices has become an intense field of investigation in which the main challenges are to keep the added value of the inorganic entities while preventing their self-aggregation within the organic matrix. We present a simple way to obtain a homogeneous highly red-NIR luminescent hybrid copolymer that contains covalently bonded nanometric-sized {Re(6)} octahedral clusters. The [Re(6)Se(i)(8)(OH)(a)(6)](4-) cluster complexes are primarily functionalized in two steps with tert-butylpyridine (TBP) and methacrylic acid (MAC) to give neutral [Re(6)Se(8)(TBP)(4)(MAC)(2)] building blocks that are copolymerized with methyl methacrylate (MMA) either in solution or in bulk in the presence of azobisisobutyronitrile as an initiator. Several samples containing 0, 0.025, 0.05, and 0.1 wt % of functionalized {Re(6)} clusters were prepared. As the {Re(6)} cluster/MMA ratio is very low, the obtained copolymers keep the entire processability of pure poly(methyl methacrylate) (PMMA), as demonstrated by differential scanning calorimetry and thermogravimetric analysis. Voltammetric and luminescence studies also indicate that the intrinsic properties of the clusters are preserved within the polymer matrix. All the samples show a bright (emission quantum yield=0.07), broad, and structureless emission band, which extends from lambda=600 nm to more than lambda=950 nm, with the maximum wavelength centered around lambda(em)=710 nm either in solution or in the solid state. Moreover, the high stability of the incorporated inorganic phosphors prevents the material from photobleaching, and thus the luminescence properties are kept entirely even after nine months of ageing.