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 (BuN)[{MoX}(OTs)] and (BuN)[{MoX}(PhSO)] (where X is Cl, Br or I; OTs is p-toluenesulfonate and PhSO 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 {MoI} cluster core. Moreover, cyclic voltammetric studies revealed that (BuN)[{MoX}(OTs)] and (BuN)[{MoX}(PhSO)] confer enhanced stability towards electrochemical oxidation relative to corresponding starting complexes (BuN)[{MoX}X].

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.

Silica nanoparticles (SNPs) doped by hexanuclear molybdenum cluster complexes [{Mo6X8}L6] n (X = Cl, Br, or I; L = various inorganic or organic ligands) have been recently suggested as materials with a high potential for biomedical applications due to both the outstanding photoluminescent properties and the 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 {Mo6I8} 4+ for such applications as bioimaging and photodynamic therapy using 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 such biomedical applications as optical bioimaging, biolabeling and photodynamic therapy.

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. The cluster [Re S (CN) ] interacts preferentially with the primary faces of the γ-CD while the bulkier clusters [Re Se (CN) ] and [Re Te (CN) ] 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 S (CN) ] or to 1D "bamboo-like" columns with [Re Se (CN) ] and [Re Te (CN) ] 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.

The mixed tellurium/selenium Re6 clusters [NMe4]4[Re6(Te8 - n Se n )(CN)6] (n = 0−8) have been prepared from the reactions of Re6Te15 with the appropriate stoichiometry of NaCN and Se at 600 °C, followed by cation exchange with NMe4Br. A typical anion comprises an Re6 octahedron with its eight faces capped by μ3-chalcogen atoms to form a pseudocube, and each Re atom has a terminal cyanide ligand. These anions have essentially idealized cubic symmetry. In the [Re6Te8(CN)6]4- anion, Re−Re bond distances range from 2.673(1) to 2.690(1) Å and Re−(μ3-Te) distances range from 2.683(1) to 2.705(1) Å. In the [Re6Se8(CN)6]4- anion the Re−Re and Re−(μ3-Se) distances range from 2.622(2) to 2.638(2) Å and 2.520(3) to 2.550(3) Å, respectively. The “[Re6Te4.34Se3.66(CN)6]4-” anion, with disordered Se/Te positions, displays intermediate bond distances with Re−Re distances ranging from 2.653(1) to 2.665(1) Å and Re−(μ3-Q) (Q = Se, Te) distances ranging from 2.581(1) to 2.673(1) Å. Whereas single-crystal X-ray diffraction results provide the barest indication of the complicated nature of the mixed Te/Se crystalline products, NMR spectroscopy indicates that they comprise cations and mixtures of geometric isomers of [Re6(Te8 - n Se n )(CN)6]4- anions (125Te NMR (δ, ppm):  [NMe4]4[Re6Te8(CN)6], −1112; [NMe4]4[Re6Te7Se(CN)6], ≥10 peaks, −643 to −1231; [NMe4]4[Re6Te4Se4(CN)6], ≥18 peaks, −705 to −1234; [NMe4]4[Re6TeSe7(CN)6], ≥12 peaks, −648 to −1114. 77Se NMR (δ, ppm):  [NMe4]4[Re6TeSe7(CN)6], ≥8 peaks, 928 to 966; [NMe4]4[Re6Se8(CN)6]·31/3H2O, 933).

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O, 4), were prepared by reactions of 1 and 2 with CsX and HX (X = Br, Cl) in an aqueous solution. Compounds 1, 2, and 4 have been characterized by the single-crystal X-ray diffraction method. Compounds 1 and 2 are crystallized in triclinic space group P1 with one formula unit in the cell of dimensions a =

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 [{MI}L] (where M is Mo or W and L is I, NO, OTs or OH/HO). This article demonstrates that despite the fact that molybdenum cluster complexes are better photoluminescence emitters, tungsten cluster complexes, in particular (BuN)[{WI}I], 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 [{MI}(NO)] was evaluated.