Yuri V. Mironov

Red‐NIR Luminescent Hybrid Poly(methyl methacrylate) Containing Covalently Linked Octahedral Rhenium Metallic Clusters

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.

Cellular uptake and cytotoxicity of octahedral rhenium cluster complexes

Cellular uptake behavior of a novel class of octahedral rhenium cluster compounds, hexahydroxo complexes K(4)[{Re(6)S(8)}(OH)(6)].8H(2)O (1) and K(4)[{Re(6)Se(8)}(OH)(6)].8H(2)O (2), was evaluated in human cervical adenocarcinoma HeLa cells. Confocal microscopy and flow cytometry studies demonstrated that rhenium cluster 1 was not internalized into cell, while rhenium cluster 2 was. Conjugation of a polymer to rhenium cluster 1, namely the derivative K(4)[{Re(6)S(8)}(OH)(5)L] (3) (L is amphiphilic diblock copolymer MPEG550-CH(2)CONH-GlyPheLeuGlyPheLeu-COO(-)), considerably enhanced cellular uptake in a concentration-dependent manner and was predominantly localized in the cytoplasm and nucleus upon incubation time. The uptake of rhenium cluster 2 was mediated by energy-dependent endocytosis, whereas rhenium cluster 3 was directly ingested into cells by cell-fusion-like mechanism. According to the cytotoxicity evaluation test, both rhenium clusters 2 and 3 did not exhibit acute cytotoxic effects up to 50 microM, at the practical concentration level of biological applications. It is, therefore, expected that the rhenium cluster complexes can be promising potential candidates as diagnostic agents for medical treatment.

Synthesis and crystal structure of a hexanuclear rhenium cluster complex Cs3K[Re6(μ3-S)6 (μ3-Te0.66S0.34)2(CN)6]. Cationic control over orientation of the cluster anion

Abstract The hexanuclear complex rhenium salt Cs3K[Re6(μ3-S)6(μ3-Te0.66S0.34)2(CN)6] ({Bd1}) has been prepared by the reaction of Re6Te15 with molten KSCN and subsequent treatment with an aqueous solution of CsCl. Its crystal structure has been determined by X-ray structural analysis. The anion has the site symmetry 3 . The Re6 octahedron is coordinated to six μ3-S and two trans mixed μ3-X ligands of the refined composition 66(3)%Te+34(3)%S. In addition there are six almost linear terminal CN ligands in its environment. The ReRe distances [2.630(2) A] in the Re3 faces capped by the μ3-X ligands are significantly longer than those in the faces capped by the μ3-S ligands [2.615(2) A].

The first water-soluble hexarhenium cluster complexes with a heterocyclic ligand environment: synthesis, luminescence, and biological properties.

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 First Octahedral Cluster Complexes With Terminal Formate Ligands : Synthesis, Structure, and Properties of K4[Re6S8(HCOO)6] and Cs4[Re6S8(HCOO)6]

The hexarhenium anionic cluster complex with terminal formate ligands [Re6S8(HCOO)6]4- was obtained by the room-temperature reaction between [Re6S8(OH)6]4- and formic acid in an aqueous solution. The cluster was crystallized as a potassium or cesium salt and characterized by X-ray single-crystal diffraction and elemental analyses, IR, 1H NMR, UV/vis, and luminescence spectroscopies. In particular, the emission quantum yield of the potassium salt of the Re6 cluster anion in the solid phase was determined for the first time. The electronic structures of [Re6S8(HCOO)6]4- and [Re6S8(OH)6]4- were also elucidated by DFT calculations.

An Unexpected Layered Structure in Inorganic Cyanide Clusters: [Cu4(μ3‐OH)4][Re4(μ3‐Te)4(CN)12]

Diffusion of aqueous solutions of K4 [Re4 Te4 (CN)12 ] and CuCl2 in the opposite direction through silica gel gives rise to the new polymer-like compound 1. This complex has a layered structure built from the interconnected cubane-like cluster cations [Cu4 (μ3 -OH)4 ]4+ and the cluster anions [Re4 Te4 (CN)12 ]4- (see picture).

Prospects of molybdenum and rhenium octahedral cluster complexes as X-ray contrast agents

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.

Excision of the {Mo6Se8} Cluster Core from a Chevrel Phase: Synthesis and Properties of the First Molybdenum Octahedral Cluster Selenocyanide Anions [Mo6Se8(CN)6]7− and [Mo6Se8(CN)6]6−

The synthesis of new molybdenum cluster selenocyanide anionic complexes [Mo6Se8(CN)6]7- and [Mo6Se8(CN)6]6- is reported. The [Mo6Se8(CN)6]7- ion was obtained by excision of the cluster core [Mo6Se8] from a Chevrel phase in the reaction of Mo6Se8 with KCN at 650 degrees C; the [Mo6Se8(CN)6]6- ion is formed by oxidation of [Mo6Se8(CN)6]7-. New cluster salts K7[Mo6Se8(CN)6] x 8H2O (1) and (Me4N)4K2[Mo6Se8(CN)6] x 10H2O (2) were isolated and their crystal structures were solved. Compound 1 crystallizes in the cubic space group Fm3m (a=15.552(2) A, Z=4, V=3761.5(8) A3), compound 2 crystallizes in the triclinic space group P1 (a=11.706(2), b=11.749(2), c=12.459(2) A, alpha=72.25(1), beta=77.51(1), gamma=63.04(1), Z=1, V=1448.5(4) A3). Compound 1 is paramagnetic due to an availability of 21 electrons per Mo6 cluster; cyclic voltammetry reveals a quasi-reversible transition [Mo6Se8(CN)6]7- [Mo6Se8(CN)6]6-, E1/2=0.63 V.

Cellular internalisation, bioimaging and dark and photodynamic cytotoxicity of silica nanoparticles doped by {Mo6I8}4+ metal clusters

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 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 {Mo6I8}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.

Novel inorganic polymeric compounds based on the Re4 chalcocyanide cluster complexes: synthesis and crystal structures of Mn2[Re4Se4(CN)12]·6H2O, Cd2[Re4Te4(CN)12]·6H2O, Cu2[Re4Te4(CN)12]·4H2O and K4Re4Se4(CN)12·6H2O

Abstract Three new tetrahedral rhenium chalcocyanide cluster compounds, Mn2[Re4Se4(CN)12]·6H2O (1), Cd2[Re4Te4(CN)12]·6H2O (2) and Cu2[Re4Te4(CN)12]·4H2O (3), exhibiting polymeric structures have been synthesized by the treatment of molecular ionic cluster compounds K4Re4Q4(CN)12 (Q=Se, Te) with aqueous solutions of Mn(NO3)2, CdSO4 and CuCl2 in gel. The previously unknown starting compound K4Re4Se4(CN)12·6H2O (4) was obtained by the reaction of Re4Se4(TeCl2)4Cl8 with KCN in water. All four compounds have been characterized by single-crystal X-ray diffraction.