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Reactivity of new tetrahedral rhenium cluster complexes with pnictogenide inner ligands μ

A series of heterometallic tetrahedral cluster complexes with the general formula [{MxRe4−xSe4}(CN)12]n− (M = Mo, W; x = 2, 3) were obtained using the reaction of ReI3 and MO3 with selenium and KCN at elevated temperatures. Compounds [ReW3Se4(CN)12]6− and [Re2W2Se4(CN)12]6− are the first rhenium–tungsten heterometallic clusters. Crystal structures, electrochemical properties in aqueous solutions and magnetic properties of crystalline samples have been studied in detail. It has been shown that new cluster anions demonstrate a regular change in geometric characteristics and redox potentials depending on the composition of the cluster core.

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 W6Q8-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 W6Q8L6 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 W6-clusters on cell viability. The results obtained clearly demonstrate their very low cytotoxicity, comparable to the least-toxic clusters presented in the literature.

The interaction of rhenium(III) halides Re3Br9 and Re3I9 with aqueous solution of sodium cyanide resulted in the formation of the first trinuclear halide-cyanide rhenium cluster complexes [{Re3X3}(CN)9]5-/[{Re3X3}(CN)9]4- (X = Br or I) crystallized as salts of the compositions Cs4Na[{Re3Br3}(CN)9]·5.25H2O (1), Cs4Na[{Re3I3}(CN)9]·6H2O (2), Cs4[{Re3Br3}(CN)9]·2H2O·0.5CsCl (3), and Cs4[{Re3I3}(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 Re3X9 by cyanides led to reduction of the original metallocluster Re39+ (12 cluster valence electrons (CVEs)) to Re37+ (14 CVEs), forming the compounds 1 and 2. The apical CN- ligands affect the electronic structure of the Re3 metallocluster stabilizing reduced form. Complexes 1 and 2 represent the first examples of triangular rhenium clusters with the Re37+ metallocluster. The reaction of 1 and 2 with H2O2 resulted in formation of compounds 3 and 4 with the formal charge of the Re3 metallocluster equal to 8+, and no further oxidation to Re39+ 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 ReI3, Se, and KCN with Sb2O3 or Bi2O3 at elevated temperature led to the formation of two new tetrahedral clusters with mixed-ligand cluster cores {Re4Se3Sb}7+ and {Re4Se3Bi}7+. Th...

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.

A reaction between ReI3 and KCN at elevated temperature led to the formation of the new cyanometalate cluster anion [{Re4(μ3-CCN)4}(CN)12]8– (1). The anion contains μ3-CCN3– ligands, which are stab...

The reaction of [Re6Se8(CN)6]4− cluster anions with Ln3+ cations in the presence of thiophene-2,5-dicarboxylate anions in an aqueous solution was studied. Two new framework compounds were synthesized and structurally characterized: [{Yb(H2O)3}2(tdc)-Re6Se8(CN)6]•10H2O (1) and CsK0,5[{Yb4(OH)4(H2O)7,5(NO3)0,5(tdc)2}{Re6Se8(CN)6}]NO3 • 16.5H2O (2) (tdc is the thiophene-2,5-dicarboxylate anion). Compound 1 crystallizes in a wide pH range (3.0–6.5) and has a porous structure with large open voids accessible to guest molecules. Compound 2 crystallizes at pH 6.0–6.5, contains polynuclear cationic complexes [Yb4(OH)4]8+, and also has a framework structure.

A series of 12 new metal–organic frameworks based on lanthanide cations (Ln = Nd, Sm–Dy), octahedral cluster anions [Re6S8(CN)6]4− or [Re6Se8(CN)6]4− and adipamide (adp) were synthesized under mild conditions in aqueous ethanol solutions. Compounds of the general composition Cs[Ln(adp)2{Re6Q8(CN)6}]·3H2O (Ln = Nd, Sm–Dy; Q = S or Se) crystallize in the hexagonal space group P6422. Despite the presence of solvate H2O molecules in structure cavities, the crystal structures revealed that the coordination environment of lanthanide cations in these 3D polymers did not contain H2O ligands. This rare feature is attributed to the combination of a bulk cluster anion and flexible adp molecules, which occupy the lanthanide coordination sphere to yield a stable lanthanide-based building block. This assumption was confirmed by synthesis of a second crystalline modification of the compound Cs[Nd(adp)2{Re6S8(CN)6}]·3H2O (orthorhombic space group Cccm). Luminescence studies evidence the presence of the typical red luminescence of hexarhenium cluster complexes and the absence of observable luminescence of lanthanide cations for all the compounds except the Nd derivatives. Magnetic data indicate very weak antiferromagnetic exchange interactions between paramagnetic Ln3+ centers.

The light-induced antibacterial and antifungal properties of A2[M6I8L6] with M = Mo and W, A = organic cation, L = ligand have been studied. The photoactive compounds (TBA)2[W6I8(C7H7SO3)6] and (TBA)2[W6I8(COOCF3)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 W6I22.

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 [{Mo5(μ3-Se)i4(μ4-Se)i(μ-pz)i4}(pzH)t5]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.

The selective preparation, structural and spectroscopic study of two new rhenium cluster complexes trans-[Re6S8(bpy)4(CN)2] and trans-[Re6S8(bpy)2(CN)4]2− (bpy = 4,4′-bipyridine) obtained by reactions of corresponding hexarhenium cyanohalides with molten bpy are reported. The complexes were crystallized as solvates, displaying supramolecular structures based on cluster units linked by numerous weak interactions with bpy molecules. The molecular compound trans-[Re6S8(bpy)4(CN)2] (1) is insoluble in water and common organic solvents, while the ionic compound trans-Cs1.7K0.3[Re6S8(bpy)2(CN)4] (2) is somewhat soluble in DMSO, DMF and N-methylpyrrolidone. The presence of the redox-active ligand bpy leads to the occurrence of multi-electron reduction transitions in a solution of 2 at moderate potential values. The ambidentate CN− ligand is the secondary functional group, which has potential for the synthesis of coordination polymers based on the new cluster complexes. In addition, both new compounds show a weak red luminescence, which is characteristic of complexes with a {Re6S8}2+ cluster core.

The paper analyzes the surface structure and phase state of Ti49.4Ni50.6 (at%) hydrogenated at 295 K in normal saline (0.9% NaCl aqueous solution with pH = 5.7) at 20 A/m2 for 0.5–6 h. The analysis shows that the average hydrogen concentration in the alloy increases with the hydrogenation time tH as follows: slowly to 50 ppm at tH = 0.5–1.5 h, steeply to 150 ppm at tH = 1.2–2 h, and linearly to 300 ppm at tH = 2–6 h. According to Bragg–Brentano X-ray diffraction data (θ–2 θ, 2 θ ≤ 50°, CoKα radiation), the alloy in its scanned surface layer of thickness ~5.6 µm reveals a TiNiHx phase with x = 0.64 and x = 0.54 after hydrogenation for 4 and 6 h, respectively. The structure of this phase is identifiable as an orthorhombic hydride similar to β1–TiFeH0.94 (space group Pmcm), rather than as a tetragonal TiNiHx hydride with x = 0.30–1.0 (space group I4/mmm). Time curves are presented to trace the lattice parameters and volume change during the formation of such an orthorhombic phase from the initial cubic B2 phase in Ti49.4Ni50.6 (at%).

New octahedral rhenium cluster complexes [{Re6Q8}(SO3)6]10- (Q = S or Se) were synthesized starting from [{Re6Q8}(H2O)4(OH)2]·12H2O. 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 (Gdx[{Re6Se8}(SO3)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 NaxGdy[{Re6Q8}(SO3)6]-based colloids with the magnetic relaxivity values of r1(2) = 21.0(24.1) and r1(2) = 25.9(29.8) mM-1 s-1 for the {Re6S8}2+ and {Re6Se8}2+ derivatives, respectively.

International audience; 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 [ReQ(CN)] with Q = S, Se, and Te were performed, leading to six new crystal structures revealing different types of supramolecular arrangements. Encapsulation of [ReQ(CN)] (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 [ReS(CN)] 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.

International audience; A number of transition metal cluster compounds can be obtained only in the melt of inorganic cyanides and, therefore, contain terminal cyanide ligands. Substitution of these ligands, which is often necessary to change the physicochemical properties of the clusters, is an urgent problem because of their low reactivity in substitution reactions. In this work, a synthetic approach has been developed for the substitution of CN-ligands in the heterometallic cluster anions [Re(3)Mo(3)Q(8)(CN)(6)](n-) (Q = S, n = 6; Q = Se, n = 5) by the 4-tert-butylpyridine (TBP) molecules. Two new compounds, namely [Re3Mo3S8(TBP)(6)] (1) and [Re3Mo3Se8(TBP)(6)] (2), were obtained with high yields and crystallized under solvothermal conditions. It has been shown that compounds 1 and 2 are based on the paramagnetic cluster cores {Re(3)Mo(3)Q(8)}(0) containing 23 cluster valence electrons (CVE). The geometry of the new compounds has been investigated using X-ray structural analysis. The electronic structure has been analyzed using the DFT calculations showing large distortion of M-6 cluster core.

Reactions of [{Re6Q8}Br6]4−/3− (Q = S, Se) with molten imidazole lead to the formation of two new neutral cluster complexes [{Re6Q8}(imzH)4(imz)2] (imzH = imidazole). The interaction of [{Re6Q8}(imzH)4(imz)2] with hydrohalic acids resulted in cationic complexes [{Re6Q8}(imzH)6]X2 (X = Cl, Br). All compounds were characterised by X-ray single-crystal and powder diffraction analyses, elemental analysis, energy dispersive X-ray and IR spectroscopies. The luminescence of the neutral compounds [{Re6Q8}(imzH)4(imz)2] was also studied.

New tetrahedral anionic rhenium cluster complexes [{Re4(PO)3(PO2)}(CN)12]8- (1) and [{Re4As2(AsO)2}(CN)12]8- (2) have been synthesized by the reaction of ReI3 with NaCN and Pred or KCN and Asgray, respectively. Compound 2 was further oxidized by aqueous H2O2 to produce the cluster anion [{Re4(AsO)4}(CN)12]8- (3). The anions contain new pnictogen/oxygen-based ligands, PO23- and AsO3-, which were stabilized by the coordination to the triangular faces of the tetrahedral Re4 metallocluster in μ3-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.

A high-temperature reactions of equimolar amounts of ReI3, As and S or Se with KCN following by recrystallization of the soluble products from water led to the formation of new cyanometallate cluster complexes K7[{Re4As3S}(CN)12]·10H2O (1) and K7[{Re4As3Se}(CN)12]·9.5H2O (2), respectively. Involvement of As2S3 instead of the mixture of As and S resulted in the formation of a cluster complex K6[{Re4As2S2}(CN)12]·3.5H2O (3). Crystal structures of the obtained compounds were investigated by the X-ray diffraction analysis. It was found that compounds 1–3 contain a new cubane cluster cores composed of the rhenium tetrahedron surrounded by the µ3-As and µ3-Q (Q = S, Se) ligands.

The cubane chalcocyanide cluster anion [Re4Te4(CN)12]4− was used as a pre-made building block for construction of a series of seven new coordination polymers (CPs) based on cationic complexes of Ln3+ ions and 1,10-phenantroline (phen). Together with three previously known compounds of this type, 1D CPs based on [Re4Te4(CN)12]4− anion formed a representative series which includes ten compounds (Ln = La, Pr, Nd, Sm–Ho, Yb). The main structural motif in the new compounds is the 1D chains composed of alternating cluster anions and [Ln(H2O)n(phen)m]3+ cationic fragments. Topology of the chains was found to be independent from the ionic radius and coordination number of the lanthanide ion. However, different number and orientation of coordinated phen and H2O molecules in the coordination environment of the lanthanide ions led to formation of several types of the supramolecular structures formed by non-covalent interactions between H2O, phen and CN− ligands. Influence of coordination environment of the lanthanide ions and conditions of the synthesis to the supramolecular structures is discussed in this work as well as structural relations with 1D coordination polymers based on mononuclear cyanometallate building blocks.

A new method is proposed for the one-step synthesis of tetrahedral rhenium chalcocyanide cluster complexes [{Re4(µ3-Q)4}(CN)12]4− (Q = S, Se, Te) using rhenium(iii) iodide as the starting compound. A cluster complex of the composition K4[{Re4S4}(CN)12]•H2O was synthesized for the first time and characterized by X-ray diffraction.

International audience; 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, evidences the self-assembly process is driven by chaotropic effect. Supramolecular approach for designing smart materials are of considerable interest on account of wide range of newfound potential applications which can be imparted in diverse fields such as medicine, energy conversion, information storage, and green catalysis. Mimicking the "lock and key" systems functioning in biological machinery such as receptor-effector recognition in proteins, 1 this conceptual approach targets to develop molecular devices built from complex self-assembled structures, 2 as tools for electronic and biological interfacing 3 or synthetic self-replicating systems. 4 Cyclodextrins (CDs) are cyclic oligosaccharides built from glucopyranose units, which have already shown to behave as effective host to encapsulate different hydrophobic entities to form biomedical drugs. 5 Recently, inorganic species such as dodecaborates, 6,7 polyoxometalates 8-11 or metal cluster complexes 12-14 were found to form inclusion complexes with one or two CDs existing both in water solution and solid-state. Solvent effects arising from these ionic species have been identified as the main contributor to the host-guest self-assembly processes in these systems. 15 More precisely, their water structure-breaking ability, namely the chaotropic effect favours creation of host-guest interface through desolvation process, resulting from the water structure reconstruction, pointed as the main contributor of the supramolecular recognition. Furthermore, the extremely large magnitude of this effect featured by highly stable supramolecular adducts allowed considering such fascinating phenomenon as an effective assembly motif in supramolecular chemistry, opening new avenues for designing multifunctional soft materials. 15 In context, special attention is given to octahedral rhenium cluster complexes [{Re 6 Q 8 }L 6 ] n due to their redox and photoluminescence properties, and high radiodensity, 16 which in combination with solubility increase in aqueous CD media are promising for numerous applications ranging from photodynamic therapy 17 or computed tomography 18 to photocatalysis. 19 Previous reports have shown the host-guest affinity depends on both inner and apical ligands of the octahedral cluster and also on the size of cyclodextrins (Fig. 1), demonstrating that several contributors operate within the host-guest recognition process. 12-14 Figure 1 Structural representations of molecular components used as guest and host units. The [{Re6Se8}(CN)6] 3-/4-cluster contains six rhenium ions (green sphere) disposed on the octahedron corners while the selenium atoms (inner ligand) are located on the eight faces of the octahedron and the terminal cyano groups (outer ligands) complete the coordination sphere of the rhenium atoms. The γ-cyclodextrin macrocycle C48H80O40 results from the condensation of eight glucopyranose units {C6H10O5} and delimits a large inner cavity of about 10 Å in diameter. Herein, we report how a single-electron transfer leading to the oxidized species [{Re 6 Se 8 }(CN) 6 ] 3-from the reduced one [{Re 6 Se 8 }(CN) 6 ] 4-affects drastically the host-guest stability in solution. While keeping constant the cluster composition and

The development of water-soluble hexanuclear cluster complexes of low toxicity is a promising task due to their potential biomedical applications such as bioimaging and photodynamic therapy. Herein, we present the syntheses of two new water-soluble hexarhenium cluster complexes with terminal amphiphilic phosphine ligands, and delineate their photoluminescence and X-ray excited optical luminescence (XEOL) properties. These cluster complexes, namely [{Re6Q8}(PPh2CH2CH2COO)6]4− (Q = S (1); Se, (2)), have the least cytotoxicity among all the tested hexanuclear metal-clusters, are capable of penetrating into cells and exhibit moderate photodynamic toxicity toward Hep-2 cells.

The energy and structural parameters were obtained for all forms of the carbonyl complex of osmium Os3(CO)12 with D3h and D3 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 Os3(CO)12 corresponds to the D3 symmetry and thus may be characterized either as left-twisted (D3S) or right-twisted (D3R). The D3S↔D3R transitions occur through the D3h transition state with an activation barrier of ~10–14 kJ/mol. Parity violation energy difference (PVED) between D3S and D3R states equals to ~5 × 10−10 kJ/mol. An unusual three-center exchange interaction was found inside the {Os3} 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 interaction of rhenium(III) halides Re

The reactions of ReI

The reaction of the K4[{Re6Si8}(OH)a6]·8H2O 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-{Re6Si8}(Pz)a2(OH)a2(H2O)a2] (1), [cis-{Re6Si8}(Pz)a2(OH)a2(H2O)a2] (2), (NO3)[cis-{Re6Si8}(Pz)a2(OH)a(H2O)a3](Pz)·3H2O (3), [Mg(H2O)6]0.5[cis-{Re6Si8}(Pz)a2(OH)a3(H2O)a]·8.5H2O (4), and K[cis-{Re6Si8}(Pz)a2(OH)a3(H2O)a]·8H2O (5). Their crystal structures are built up from trans- or cis-[{Re6Si8}(Pz)a2(OH)a4−x(H2O)ax]x−2 cluster units. The cohesions of the 3D supramolecular frameworks are based on stacking and H bonding, as well as on H3O2−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.

Compounds based on new cyanide cluster anions [{Mo6I8}(CN)6]2&ndash, trans-[{Mo6I8}(CN)4(MeO)2]2&ndash, and trans-[{W6I8}(CN)2(MeO)4]2&minus, 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 {Mo6I8}4+ and {W6I8}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 {Mo6I8} and {W6I8} 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

A reaction between ReI

Substitution of terminal halide ligands of octahedral rhenium cluster complexes [Re6Q8X6]4– in a melt of 4,4′-bipyridine (bpy) led to us obtaining four new compounds with the general formula trans-...

Silica nanoparticles (SNPs) doped by hexanuclear molybdenum cluster complexes [{Mo

The light-induced antibacterial and antifungal properties of A

International audience; 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 [PWO] and electron-rich rhenium clusters. It is worth noting that a cluster-based cation [{ReSe}(HO)] on one hand and a cluster-based anion on the other hand [{ReSe}(CN)] 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[{ReSe}(HO)]{[PWO]@2γ-CD}·42HO, 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 [PWO] with the anionic rhenium cluster [{ReSe}(CN)] is also achieved with γ-CD despite the repulsive forces between the nanosized anions. The resulting solid, K{[{ReSe}(CN)]@2γ-CD}[PWO]·33HO, is built from 12 inclusion complexes {[{ReSe}(CN)]@2γ-CD} 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.

First examples of Ag(I)-containing coordination polymers based on octahedral rhenium(III) chalcocyanide clusters, namely [{Ag(bpy)}{Ag4(bpy)4(μ-CN)}{Re6Q8(CN)6}] (Q = S in 1 or Se in 2; bpy = 2,2′-bipyridine), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, elemental and thermogravimetric analysis, EDS, IR and luminescence spectroscopy. The compounds are isostructural, crystallize in the orthorhombic system (space group Pccn, Z = 4) and possess a rigid 3D framework structure built up from {Re6Q8(CN)6}4– cluster anions and two distinct types of Ag(I)-containing cationic units, mononuclear {Ag(bpy)}+ and tetranuclear {Ag4(bpy)4(μ-CN)}3+, all of which are interconnected through cyanide bridging. The supramolecular structures of 1 and 2 are supported by argentophilic Ag⋯Ag interactions, but surprisingly show very limited π-π stacking of the pyridine rings. Both compounds are highly emissive in red region showing the longest lifetimes hitherto reported for the solid samples of hexarhenium cluster compounds.

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 [{W6 I8 }(DMSO)6 ](NO3 )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.

A first method for obtaining of electron-rich bioctahedral rhenium clusters has been developed. Two cluster salts, namely (Et3NH)4(Me2NH2)4[Re12CS14(µ-S)3Cl6] (1) and (Et4N)4(Me2NH2)4[Re12CS14(µ-S)3Br6] (2), have been synthesized and isolated in the solid state. Single-crystal X-ray diffraction showed that salts 1 and 2 are based on the new cluster anions [Re12CS14(µ-S)3Cl6]8− and [Re12CS14(µ-S)3Br6]8− containing 48 cluster valence electrons (CVE). The correlations between geometry and CVE number of the bioctahedral chalcohalide anions have been examined using the DFT calculations. The dissolution of the salts 1 and 2 is accompanied by the oxidation yielding the [Re12CS14(µ-S)3Cl6]6− and [Re12CS14(µ-S)3Br6]6− anions. Properties of the new clusters in the DMSO solutions have been investigated by UV–Vis spectroscopy and cyclic voltammetry. The latter revealed the presence of multiple reversible one-electron redox waves in a narrow potential window.

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.

In this work, we demonstrate influence of the source of organic ligand on the formation of supramolecular structures based on the octahedral metal clusters. Two series of coordination polymers based on the rhenium clusters [Re6Se8(CN)6]4– and Ln3+ complexes (Ln = Sm, Eu, Tb, Dy) with dimethylformamide (DMF) were obtained. The first series was obtained by direct addition of DMF in the reaction mixture. The series consist of the compounds crystallizing in trigonal crystal system, R3c space group, and possessing a framework porous structures composed of cluster anions and [Ln(dmf)3(H2O)2]3+ complexes. Compounds of the second series were obtained as a result of in situ generation of DMF by hydrolysis of N,N-dimethylformamide dimethyl acetal (DMF DMA). These compounds were crystallized in orthorhombic crystal system, Pnma space group, and possessed a layered structure consisting of cluster anions and [Ln(dmf)2(H2O)2]3+ complexes. It was found that the difference in the structures formed depends on the source of DMF rather than other reaction conditions.

This paper presents experimental data on the microstructure and martensite transformation temperatures of Ti49.8Ni50.2 (at%) after abc pressing (multi-axial forging) to different true strains e from 1.84 to 9.55 at 573 K. The data show that increasing the true strain results in grain–subgrain refinement on different scales at a time. With e = 9.55 at 573 K, the average grain–subgrain size measured approximately 130 nm. Decreasing the abc pressing temperature from 723 to 573 K caused a decrease in all martensite transformation temperatures, a change in the lattice parameters, R phase formation, and angular shifts of diffraction peaks and their broadening. The largest change in the microstructure of Ti49.8Ni50.2 was provided by abc pressing to e = 1.84. Increasing the true strain to e = 9.55 resulted in a much smaller effect, suggesting that the alloy obtained a high density of structural defects even at e = 1.84. Two possible mechanisms of grain–subgrain refinement are discussed.