V. E. Fedorov

One-Step Exfoliation Synthesis of Easily Soluble Graphite and Transparent Conducting Graphene Sheets

Easily soluble expanded graphite is synthesized in a one-step exfoliation process that can be used for the lowcost mass production of graphene for various applications because of the simplicity and speed of the process. The graphene obtained is sufficiently expanded to be dispersed in aqueous solutions with an ordinary surfactant and in organic solvents.

A Novel Framework Type for Inorganic Clusters with Cyanide Ligands: Crystal Structures of Cs2Mn3[Re6Se8(CN)6]2⋅15 H2O and (H3O)2Co3[Re6Se8(CN)6]2⋅14.5 H2O

Large cavities occupied by cations and water molecules are part of the polymeric inorganic cluster structure made up of [Re6Se8(CN)6]4− and M2+ ions (M=Mn, Co; see structure on the right). Remarkably, the water molecules play an essential role in the stabilization of the structure: When the cluster is heated to 80–160°C, water is lost irreversibly, and a sharp change in structure is observed.

Octahedral rhenium(III) chalcocyanide cluster anions: Synthesis, structure, and solid state design

The review summarizes data on synthesis and structure of rhenium chalcocyanide cluster onions [ Re6X8(CN)6]4-f (X = S, Se, Te) belonging to a new class of inorganic compounds. Two main groups of such compounds are considered: salts with an island structure and polymer compounds. Various factors governing the type of structure and the dimensionality of the polymer compounds are analyzed, including the nature of the chalcogen atom in the cluster anion, preferable coordination of the transition metal cation, and the size of additional charge-compensating cations. Crystal-chemical approaches to design of complex salts based on octahedral rhenium chalcocyanide cluster anions are formulated.

The superior dispersion of easily soluble graphite

Graphene is a 2D one-atom-thick layer that has attracted enormous scientific attention on account of its extraordinary electronic and mechanical properties resulting from the hexagonally arrayed sp-hybridized carbon atom structure. Several efforts have been made to use graphene in devices and composites. The strong covalent bonds of carbon atoms provide high mechanical and thermal properties and chemical stability. The theoretical Young’s modulus of graphene is approximately 1060GPa. In addition, the high electrical conductivity (mobility: 20 000 cmV 1 s , velocity: c/300) through the p-electron cloud makes graphene a promising material in conducting composites and quantum electronics. As in other new materials (such as carbon nanotubes, various quantum dots, etc.), the development of mass productionmethods that can support the demand for graphene in a variety of large-scale applications is of high priority. Thus far, several methods for graphene production have been developed and can be summarized into three areas:mechanical exfoliation, graphene in solution, and epitaxial growth. Mechanical exfoliation produces the highest quality graphene, which is suitable for fundamental studies. Epitaxial growth provides the shortest path to graphene-based electronic circuits. Graphene in solution can offer lower costs and higher throughputs and may be used in a wide range of applications because of the significant practical utility of this material. However, the method is quite complicated and

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.

Chemically modified graphene sheets by functionalization of highly exfoliated graphite

Highly exfoliated graphite (HEG) containing multi-, bi- and monolayer graphenes has been prepared from an alternative class of precursors – fluorinated graphite intercalation compounds, namely, poly(dicarbon fluoride) intercalation compounds C2F·xR. Treatment of HEG by mixture of concentrated nitric and sulfuric acids results in chemically modified graphenes (CMG) dispersible in water or alcohol medium without any surfactants or stabilizers. The samples were examined by elemental analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), IR, Raman and UV-vis spectroscopies. Elemental analysis and IR data indicate that covalent functionalization with oxygen-containing groups, such as carboxyl group, occurs upon acid treatment. AFM images show thin sheets of about 1 nm, confirming the well-dispersed state of the material. Dispersions of CMG sheets from highly exfoliated graphite are very stable colloids (over a year) and can serve for further functionalization.

Inorganic Coordination Polymers Based on Chalcocyanide Cluster Complexes

The paper reports results of experiments involving design of inorganic coordination polymers based on tetrahedral and octahedral chalcocyanide cluster complexes as building blocks. Various approaches to designing three‐dimensional, layered, and chain‐like structures are discussed. Structures of various types are described, and prospects of further studies in this field are outlined.

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.