Hexamolybdenum Clusters Research Articles

Enhanced photoluminescence of hexamolybdenum cluster by anodic aluminum oxide photonic crystals

The enhanced photoluminescence of the Mo6 cluster was first reported by its incorporation into the anodic aluminum oxide (AAO), a photonic structure to delocalize the emission light. Two AAO structures with different pore sizes, densities, and shapes were controlled by pore widening treatment. The deposition of the negatively charged clusters at the bottom of the ordered AAO resulted in narrowing the PL peak at 680 nm with an enhanced intensity of 230 %. In addition, the disordered AAO supported the deposition of clusters on the surface that efficiently adjusted the shift of the PL peak position, obtaining a high intensity by more than 300 % in comparison with that of clusters deposited on the ITO-coated glass. The cluster-integrated photonic crystal could be an interesting material for applications that require efficient luminescence.

Light harvesting hexamolybdenum cluster integrated with the 3D ordered semiconductor inverse opals for optoelectronic property

Solar energy-harvesting materials have significantly contributed to the development of energy-saving applications for several decades. We have mainly used a new concept composed of the electrophoretic deposition technique and photonic crystal structural engineering to understand the tunable light-absorption and electronic conduction properties. A hexamolybdenum cluster compound (denoted as the Mo6 cluster) was successfully functionalized on a tin pyrophosphate semiconductor integrated within an inverse opal photonic crystal. The size of the periodical pores, surface modification, and chemical composition of the infiltration material of the inverse opal film have been investigated to control the photonic bandgap in the visible range and the efficiency of the deposited Mo6 cluster. The photoactive Mo6 clusters act as a visible light harvester and generate an efficient photo-induced current upon light absorption that is enhanced by a slow photon effect occurring at the photonic stopband edges. The electron and proton are transferred in the inorganic-organic network via hydrogen bonds by a hopping mechanism to generate a rapid photoconductivity response during light irradiation. Specific attention focused on the role of humidity and temperature regarding the reproducibility of the experiments and the photosensitivity of the nanocomposite. The suitable tunable photo-induced conduction property in organic-inorganic materials opens a new opportunity for the applicability of cluster-based compounds in visible optoelectronic devices.

Enhancement of photoactivity and cellular uptake of (Bu4N)2[Mo6I8(CH3COO)6] complex by loading on porous MCM-41 support. Photodynamic studies as an anticancer agent

The incorporation by ionic assembly of the hexanuclear molybdenum cluster (Bu 4 N) 2 [Mo 6 I 8 (CH 3 CO 2 ) 6 ] ( 1 ) in amino-decorated mesoporous silica nanoparticles MCM-41 , has yielded the new molybdenum-based hybrid photosensitizer 1@MCM-41 . The new photoactive material presents a high porosity, due to the intrinsic high specific surface area of MCM-41 nanoparticles (989 m 2 g −1 ) which is responsible for the good dispersion of the hexamolybdenum clusters on the nanoparticles surface, as observed by STEM analysis. The hybrid photosensitizer can generate efficiently singlet oxygen, which was demonstrated by using the benchmark photooxygenation reaction of 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABDA) in water. The photodynamic therapy activity has been tested using LED light as an irradiation source (λ irr ~ 400–700 nm; 15.6 mW/cm 2 ). The results show a good activity of the hybrid photosensitizer against human cervical cancer (HeLa) cells, reducing up to 70 % their viability after 20 min of irradiation, whereas low cytotoxicity is detected in the darkness. The main finding of this research is that the incorporation of molybdenum complexes at porous MCM-41 supports enhances their photoactivity and improves cellular uptake, compared to free clusters. Incorporation of photoactive molybdenum complexes at porous MCM-41 supports enhance their photoactivity and improves cellular uptake. • A hexanuclear molybdenum cluster has been incorporated in amino-decorated mesoporous silica nanoparticles. • The new photoactive material can generate efficiently singlet oxygen upon illumination with white light. • The photodynamic therapy activity has been tested with HeLa cells, reducing up to 70 % their viability. • The incorporation of molybdenum complexes at porous supports enhances their photoactivity and improves cellular uptake.

Anticancer potential of hexamolybdenum clusters [{Mo6I8}(L)6]2− (L = CF3COO− and C6F5COO−) incorporated into different nanoparticulate forms

The work for the first time highlights the specific nanoparticulate form of hexamolybdenum cluster complexes [{Mo6I8}(L)6]2− with L = CF3COO− and C6F5COO− (Mo6) exhibiting high anticancer potential in the irradiation-free conditions. The diverse nanoparticulate forms developed from the Mo6-units include self-aggregated (Bu4N)2[{Mo6I8}(L)6 (Mo6-aggregates) and those deposited onto the specifically decorated silica nanoparticles (SNs). The chemical and colloid stabilities of the as prepared nanoparticles reveal both Mo6-aggregates and those deposited onto the preliminary hydrophilized by polyethyleneimine (PEI) SNs (Mo6-PEI-SNs) as optimal candidates for biomedical applications. High photodynamic activities of Mo6-aggregates and Mo6-PEI-SNs revealed by the spin trap facilitated ESR technique along with the efficient irradiation-induced cytotoxic effects of both nanoparticulate forms indicate their great potential in photodynamic therapy. However, “dark” cytotoxicity measurements for M−HeLa cancer and Chang Liver normal cell lines revealed significant specific anticancer effect of Mo6-aggregates, but the insignificant one of Mo6-PEI-SNs. Quantitative LysoTracker-facilitated colocalization analysis in lysosomal compartments highlighted the highest lysosomal localization of Mo6-aggregates for L = CF3COO−, to a lesser degree for L = C6F5COO−, for Mo6-PEI-SNs being the lowest. The great anticancer effect of the Mo6-aggregates correlates with their highest localization in lysosomal compartment followed by the enhanced aggregation, in turn, derived from the hydrophobic apical ligands.

Structure impact on photodynamic therapy and cellular contrasting functions of colloids constructed from dimeric Au(I) complex and hexamolybdenum clusters

Electrostatically driven self-assembly of [Au2L2]2+ (L is cyclic PNNP ligand) with [{Mo6I8}(L')6]2− (L' = I−, CH3COO−) in aqueous solutions is introduced as facile route for combination of therapeutic and cellular contrasting functions within heterometallic colloids (Mo6-Au2). The nature of L' affects the size and aggregation behavior of crystalline Mo6-Au2 aggregates, which in turn affect the luminescence of the cluster units incorporated into Mo6-Au2 colloids. The spin trap facilitated electron spin resonance spectroscopy technique indicates that the level of ROS generated by Mo6-Au2 colloids is also affected by their size. Both (L' = I−, CH3COO−) Mo6-Au2 colloids undergo cell internalization, which is enhanced by their assembly with poly-DL-lysine (PL) for L' = CH3COO−, but remains unchanged for L' = I−. The colloids PL-Mo6-Au2 (L' = CH3COO−) are visualized as huge crystalline aggregates both outside and inside the cell cytoplasm by confocal microscopy imaging of the incubated cells, while the smaller sized (30–50 nm) PL-Mo6-Au2 (L' = I−) efficiently stain the cell nuclei. Quantitative colocalization analysis of PL-Mo6-Au2 (L' = CH3COO−) in lysosomal compartments points to the fast endo-lysosomal escape of the colloids followed by their intracellular aggregation. The cytotoxicity of PL-Mo6-Au2 differs from that of Mo6 and Au2 blocks, predominantly acting through apoptotic pathway. The photodynamic therapeutic effect of the PL-Mo6-Au2 colloids on the cancer cells correlates with their intracellular trafficking and aggregation.

ROS-generation and cellular uptake behavior of amino-silica nanoparticles arisen from their uploading by both iron-oxides and hexamolybdenum clusters.

The present work introduces combination of superparamagnetic iron oxides (SPIONs) and hexamolybdenum cluster ([{Mo6I8}I6]2-) units within amino-decorated silica nanoparticles (SNs) as promising design of the hybrid SNs as efficient cellular contrast and therapeutic agents. The heating generated by SNs doped with SPIONs (Fe3O4@SNs) under alternating magnetic field is characterized by high specific absorption rate (SAR=446W/g). The cluster units deposition onto both Fe3O4@SNs and "empty" silica nanoparticles (SNs) results in Fe3O4@SNs[{Mo6I8}I6] and SNs[{Mo6I8}I6] with red cluster-centered luminescence and ability to generate reactive oxygen species (ROS) under the irradiation. The monitoring of spin-trapped ROS by ESR spectroscopy technique indicates that the ROS-generation decreases in time for SNs[{Mo6I8}I6] and [{Mo6I8}I6]2- in aqueous solutions, while it remains constant for Fe3O4@SNs[{Mo6I8}I6]. The cytotoxicity is low for both Fe3O4@SNs[{Mo6I8}I6] and SNs[{Mo6I8}I6], while the flow cytometry indicates preferable cellular uptake of the former versus the latter type of the nanoparticles. Moreover, entering into nucleus along with cytoplasm differentiates the intracellular distribution of Fe3O4@SNs[{Mo6I8}I6] from that of SNs[{Mo6I8}I6], which remain in the cell cytoplasm only. The exceptional behavior of Fe3O4@SNs[{Mo6I8}I6] is explained by residual amounts of iron ions at the silica surface.

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 (Bu4N)2[{Mo6I8}(NO3)6]/acetone solution. Successful cluster immobilization and chemical composition of the samples were verified by inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy with elemental mapping (TEM/EDS), X-ray photoelectron spectroscopy (XPS), and optical diffuse-reflectance spectroscopy. A small amount of water in acetone initiates the hydrolysis of a molybdenum cluster precursor with labile NO3- ligands, which are absent in the final composite, according to the XPS data. Intermediate hydrolyzed cluster forms anchor to the surface of h-BN nanosheets and promote growth of the insoluble compound [{Mo6I8}(H2O)2(OH)4]·yH2O as the final hydrolysis product. TEM/EDS proves that the cluster exists at the nanosheet surface in the form of an X-ray diffraction amorphous thin film. The samples obtained show high photocatalytic activity in the degradation of a model pollutant rhodamine B under UV- and visible-light irradiation. The materials retain their initial photocatalytic efficacy during at least six cycles without the need for recovery.

Interfacial uploading of luminescent hexamolybdenum cluster units onto amino-decorated silica nanoparticles as new design of nanomaterial for cellular imaging and photodynamic therapy

The present work introduces a facile synthetic route to embed phosphorescent K2[{Mo6I8}I6] and (nBu4N)2[{Mo6I8}(CH3COO)6] clusters (C) onto silica-water interface of amino-decorated silica nanoparticles (SNs, 60 ± 6 nm). The assembled C-SNs gain in the luminescence intensity, which remains stable within three months after their assembly. High uptake capacity of the clusters (8700 of K2[{Mo6I8}I6] and 6500 of (nBu4N)2[{Mo6I8}(CH3COO)6] per the each nanoparticle) derives from ionic self-assembly and coordination bonds between the cluster complexes and ionic (amino- and siloxy-) groups at the silica surface. The coordination via amino- or siloxy-groups restricts aquation and hydrolysis of the embedded clusters, in comparison with the parent K2[{Mo6I8}I6] and (nBu4N)2[{Mo6I8}(CH3COO)6. High potential of the assembled nanoparticles in the ROS generation was revealed by EPR measurements facilitated by spin trapping. The high positive charge and convenient colloid stability of the assembled C-SNs hybrids are the prerequisite for their efficient cellular uptake, which is exemplified in the work by MCF-7 cell line. The measured dark and photoinduced cytotoxicity of the C-SNs hybrids reveals significant photodynamic therapy effect on the MCF-7 cancer cell line versus the normal cells. This effect is entirely due to the embedded clusters and is dependent on the chemical composition of the cluster.

Nanosized mesoporous metal–organic framework MIL-101 as a nanocarrier for photoactive hexamolybdenum cluster compounds

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.

Hexamolybdenum clusters supported on graphene oxide: Visible-light induced photocatalytic reduction of carbon dioxide into methanol

Hexamolybdenum (Mo6) cluster-based compounds namely Cs2Mo6Bri8Bra6 and (TBA)2Mo6Bri8Bra6 (TBA=tetrabutylammonium) were immobilized on graphene oxide (GO) nanosheets by taking advantage of the high lability of the apical bromide ions with oxygen-functionalities of GO nanosheets. The loading of Mo6 clusters on GO nanosheets was probed by Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and elemental mapping analyses. The developed GO-Cs2Mo6Bri8Brax and GO-(TBA)2Mo6Bri8Brax composites were then used as heterogeneous photocatalysts for the reduction of CO2 under visible light irradiation. After 24h visible light illumination, the yield of methanol was found to be 1644 and 1294μmolg−1cat for GO-Cs2Mo6Bri8Brax and GO-(TBA)2Mo6Bri8Brax, respectively. The quantum yields of methanol by using GO-Cs2Mo6Bri8Brax and GO-(TBA)2Mo6Bri8Brax as catalysts with reference to Mo6 cluster units presented in 0.1g amount of catalyst were found to be 0.015 and 0.011, respectively. The role of immobilized Mo6 clusters-based compounds on GO nanosheets is discussed to understand the photocatalytic mechanism of CO2 reduction into methanol.

Hexamolybdenum Cluster Complexes with Pyrene and Anthracene Carboxylates: Ultrabright Red Emitters with the Antenna Effect

AbstractPhosphorescent hexamolybdenum cluster complexes with pyrene and anthracene carboxylates exhibit energy transfer from the grafted ligands to the {Mo6I8} core. The complex with the pyrene ligands exhibits the highest brightness of emission ever reported for a Mo6 cluster complex excited in the near‐UV region (ϵ355 = 2.3 105 M–1 cm–1, ΦL = 0.60). These antenna systems possess attractive features as UV/Red light convertors, optical oxygen sensors, or sensitizers of singlet oxygen.

A highly emissive inorganic hexamolybdenum cluster complex as a handy precursor for the preparation of new luminescent materials

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.

Root uptake and phytotoxicity of nanosized molybdenum octahedral clusters

Here are examined the root uptake and phytotoxicity of octahedral hexamolybdenum clusters on rapeseed plants using the solid state compound Cs2Mo6Br14 as cluster precursor. [Mo6Br14]2− cluster units are nanosized entities offering a strong and stable emission in the near-infrared region with numerous applications in biotechnology. To investigate cluster toxicity on rapeseed plants, two different culture systems have been set up, using either a water-sorbing suspension of cluster aggregates or an ethanol-sorbing solution of dispersed nanosized clusters. Size, shape, surface area and state of clusters in both medium were analyzed by FE-SEM, BET and XPS. The potential contribution of cluster dissolution to phytotoxicity was evaluated by ICP-OES and toxicity analysis of Mo, Br and Cs. We showed that the clusters did not affect seed germination but greatly inhibited plant growth. This inhibition was much more important when plants were treated with nanosized entities than with microsized cluster aggregates. In addition, nanosized clusters affected the root morphology in a different manner than microsized cluster aggregates, as shown by FE-SEM observations. The root penetration of the clusters was followed by secondary ion mass spectroscopy with high spatial resolution (NanoSIMS) and was also found to be much more important for treatments with nanosized clusters.

Hydrogen-Bonded Hexamolybdenum Clusters: Formation of Inorganic-Organic Networks This work was supported by the National Science Foundation (grant CHE-9417250).

An extended array of clusters held together by hydrogen bonds is exhibited by (cryptNa)2[Mo6Cl8(OC6H4CONH2)6] (1, structure shown; crypt=cryptand). Depending on the crystallization conditions, 1 can adopt two different packing structures with different channel sizes between the layers. The structures and photophysical properties of 1 are discussed.

Hydrogen-Bonded Hexamolybdenum Clusters: Formation of Inorganic–Organic Networks

Hydrogen-Bonded Hexamolybdenum Clusters: Formation of Inorganic–Organic Networks

Hexamolybdenum Cluster with One Telluride and Seven Chloride Capping Ligands

Tetraethylammonium hepta-μ 3 -chloro-μ 3 -telluro-hexachlorohexamolybdate, (Et 4 N) 3 [(Mo 6 Cl 7 Te)Cl 6 ], has an octahedral hexamolybdenum cluster core whose faces are capped by seven Cl atoms and one Te atom. The capping telluride is disordered in the crystal. The average Mo-Mo distance is not much different from those in [(Mo 6 Cl 7 Z)Cl 6 ] 3- (Z = S, Se).

Influence of a Neutral Terminal Ligand on the Structure and Redox Potential of the Hexamolybdenum(12+) Cluster Ion with Mixed Capping Ligand

Abstract A hexamolybdenum cluster complex of (n-Bu4N)2[(Mo6Br7S)Cl5(CH3CN)] was synthesized, and its crystal structure was determined. The Mo–Mo distance (2.637(7) Å) is similar to that of (Et4N)3[(Mo6Br7S)Cl6]. The oxidation potential is higher than that of [(Mo6Br7S)Cl6]3− by 0.21 V. The shift of potential may be caused by change of net charge of the cluster anion.

Preparation and structural characterization of a hexanuclear molybdenum (II) cluster containing carboxylate ligands (Bu4N)2[Mo6(?3-Cl)8(O2CMe)6

The hexamolybdenum cluster complex [Mo6(μ3-Cl)8(O2CMe)6]2−, 1 was isolated as the Bu4N+ salt in 71% yield from the reaction of (Bu4N)2[Mo6(μ3-Cl)8Cl6] with AgO2CMe in CH2Cl2 solvent. The compound was characterized by single crystal X-ray diffraction analysis. The cluster contains an octahedral arrangement of six molybdenum atoms with eight chloride ligands bridging the eight trianglar faces and six carboxylate ligands terminally coordinated through one oxygen atom to each of the six molybdenum atoms. Crystal data: space group =P21/n,a=10.713(3)A,b=14.43(1)A,c=21.919(4)A, β=94.37(2)°,Z=2, 1965 reflections,R=0.036.

Synthesis, structure, and properties of oxidized hexamolybdenum clusters [(Mo6X7Y)X'6]2- (X = X' = Cl, Br; Y = S, Se)

The synthesis, structure, and properties of Mo 6 (13+) species, which are obtained by the oxidation of Mo 6 (12+) species [(Mo 6 X 7 Y)X' 6 ] 3- (X=X'=Cl, Br; Y=S, Se), are reported. (n-Bu 4 N) 2 [(Mo 6 Cl 7 S)Cl 6 ] crystallizes in the monoclinic space group P2 1 /n with a=18.542 (2) A, b=11.701 (2) A, c=12.806 (2) A

ChemInform Abstract: Syntheses and Properties of Monochalcogenide‐Substituted Hexamolybdenum Halide Clusters.

AbstractThe hexamolybdenum clusters (IVa) and (IVb) have been prepared as shown in the scheme.