Molecular Cluster Compounds Research Articles

Isolation of an organometallic yttrium bismuth cluster and elucidation of its electronic structure

A rare molecular cluster compound of bismuth and yttrium, [K(THF)4][Cp*2Y2Bi6], featuring a bridging cyclohexane-like Bi66− chair, was isolated and characterised via single-crystal X-ray diffraction analysis, UV-Vis spectroscopy and DFT calculations.

Towards rationalizing photoswitchable behavior of Cu[formula omitted]Mo[formula omitted] cyanido-bridged molecule

[CuII(enpnen)]2[MoIV(CN)8]⋅7H2O (enpnen = N,N′ - bis(2- aminoethyl)- 1,3 - propane-diamine) molecular cluster compound (1) was subject to a series of irradiations with the light of 405 nm. On irradiation isothermal magnetization at 1.8 and 5 K in the field range 0–70 kOe as well as magnetic susceptibility in the temperature range of 2–300 K were subsequently detected. Both types of magnetic signals were next analyzed assuming that the irradiation triggers two independent processes: the metal to metal charge transfer (MMCT) leading to a state with the Arrhenius-type relaxation and the spin crossover (SC) transition ending in a state whose relaxation displays a threshold behavior. The first mechanism leads to an electron from the spinless Mo(IV) configuration being transferred to one of the Cu(II) ions transforming the trimer into the state Cu(II)-N-C-Mo(V)-C-N-Cu(I), with spin 1/2 on the Mo(V) ion and the spinless Cu(I) ion. The other mechanism gives rise to an excited paramagnetic Mo(IV)∗ linked to two paramagnetic Cu(II) centers with a possible superexchange interaction. The spin of the excited Mo(IV)∗ species is equal to 1 and associated to a disruption of the 5s-electronic pair. A reasonable result of simultaneous fitting the full series of susceptibility and magnetization data to the model taking into account both mechanisms corroborates their presence.

Ionic Liquid-Driven Formation of and Cation Exchange in Layered Sulfido Stannates - a CH2 Group Makes the Difference.

Two types of layered sulfido stannates or a molecular cluster compound are obtained upon ionothermal treatment of the simple sulfido stannate salt K4[SnS4] · 4H2O that is based on binary tetrahedral [SnS4]4− anions. The formation of the respective products, novel compounds (C4C1C1Im)2[Sn3S7] (1 a), (C4C1C2Im)2[Sn3S7] (1 b), and (C4C1C2Im)2[Sn4S9] (2) with layered anionic substructures, or the recently reported compound (C4C1C1Im)4+x[Sn10O4S16(SMe)4][An]x (A) comprising a molecular cluster anion, is controlled by both the choice of the ionic liquid cation and the reaction temperature. We report the scale‐up of the syntheses by a factor of 100 with regard to other reported ionothermal syntheses of related compounds, and a procedure of how to isolate them in phase‐pure form – both being rare observations in chalcogenido stannate chemistry in ionic liquids. Moreover, the synthesis of compound 1 a can be achieved by rapid cation exchange starting out from 1 b, which has not been reported for organic cations in any chalcogenido stannate salt to date.

BiVO4-Polyoxometalate Composite Film Photoanode for Photoelectrochemical Phenol Sensing

Currently widespread environmental pollutants have caused serious risks to the health of living things and humans. In particular, various toxic pollutants resulting from industrial factories were constantly discharged into environment. Phenol is natural or anthropogenic origin and usually obtained from petroleum or coal tar and are widely used in chemical, petro-chemical as well as pharmaceutical industries. Phenol as pollutant in water is also related with these industrial processes. The presence of phenols in the environment creates health concerns due to their toxicity; e.g., phenol is acting corrosively in contact with skin and mucosal membranes. Also, phenol is highly water-soluble leading to increased environmental risks. Therefore, it is vital to develop a facile and efficient analysis method to detect phenol concentration in aqueous solution. Photoelectrochemical sensing is a new-fashioned analytical method, which may find promising application in sensing in virtue of its high response, low cost and easy fabrication.Recently, bismuth vanadate (BiVO4) as an n-type semiconducting material of narrow band gap has attracted wide attention owing to its superior properties of non-toxic, low-cost, high stability and excellent photoelectrochemical performance. Polyoxometalates (POM), a class of molecular metal-oxo cluster compounds based mainly on Mo, W, and V elements, have shown promising application prospect in fields of catalysis, medicine, and materials science owing to their superior physicochemical properties. Especially, POM clusters can act as efficient electron acceptor dopant in semiconductor composite materials, and then POM have the ability to capture and transport photogenerated electrons from the conduction band (CB) of semiconductor; this thus reduces the electron-hole recombination and enhances photoelectric conversion efficiency of semiconductor materials. In this work, combining the advantages of both BiVO4 and POM, we prepared the BiVO4/PW12 composite film photoanode, and investigated its performance for photoelectrochemical phenol sensing. Bismuth vanadate nanotubes were prepared by heating reflux method. PW12 was introduced to BiVO4 and BiVO4/PW12 composite film electrode sensors by means of electrodeposition. At room temperature, a three-electrode system was used to test the concentration of phenol in the sensing solution by using BiVO4 and BiVO4/PW12 composite film electrodes as working electrodes. Through the experiment, it was found that both BiVO4 and BiVO4/PW12 sensor composite film electrodes were responsive to the concentration of phenol in solution. The BiVO4/PW12 composite film sensor showed excellent performance of sensing phenol concentration in aqueous solution, and the linear correlation reached 99.16%. When the concentration of phenol was 100 mg•L, the response of BiVO4/PW12 composite film electrode to the solution was 1.778, which was about 3.6 times higher than that of the pure BiVO4 electrode. The results from this work show an effective photoelectrochemical sensing method of phenol detection. Figure 1

Synthesis and structural characterization of a multi-component co-crystal: the cluster compound [Cu6In2(PPh3)2(µ-SeR)6(µ3-SeR)4BrBr0.35/(SeR)0.65] (R = p-Me2NC6H4)

In order to improve our contribution in the field of main-group-semiconductor cluster compounds we present the synthesis and structural characterization of [p-Me2NC6H4Se]2 (1) and [Cu6In2(PPh3)2(µ-SeR)6(µ3-SeR)4Br(Br0.35/{SeR}0.65)] (2)—in which R = p-Me2NC6H4. X-ray analysis of 2 indicated that the single crystals obtained from the reaction of InBr, [p-Me2NC6H4Se]2, and Cu(PPh3)Br are formed by 35% of the compound with the molecular formula [Cu6In2(PPh3)2(µ-SeR)6(µ3-SeR)4Br2)] and 65% of the compound with the molecular formula [Cu6In2(PPh3)2(µ-SeR)6(µ3-SeR)4BrSeR]. The existence of two different molecular cluster compounds in the same crystal structure is a rare kind of multi-component co-crystal for this class of compounds. Additionally, the band-gap energy of 2 was estimated by UV–vis spectroscopy in the solid state.

Synthesis of a Cyclic Co2Sn2 Cluster Using a Co- Synthon.

[Ar′SnCo]2 (1, Ar′ = C6H3-2,6{C6H3-2,6-iPr2}2), a rare metal–metal bonded cobalt–tin cluster with low-coordinate tin atoms, was prepared by the reaction of [K(thf)0.2][Co(1,5-cod)2] (cod = 1,5-cyclooctadiene) with [Ar′Sn(μ-Cl)]2. This reaction illustrates a promising synthetic strategy to access uncommon metal clusters. The structure of 1 features a rhomboidal Co2Sn2 core with strong metal–metal bonds between tin and cobalt and a weaker tin–tin interaction. Reaction of 1 with white phosphorus afforded [Ar′2Sn2Co2P4] (2), the first molecular cluster compound containing phosphorus, cobalt and tin.

Silver Thiolate Nano-sized Molecular Clusters and Their Supramolecular Covalent Frameworks: An Approach Toward Pre-templated Synthesis.

A series of seven new complexes including silver-thiolate molecular clusters and their covalent supramolecular frameworks have been assembled from the silver carbide precursor Ag2 C2 using a C22- pre-templated approach. Herein, two prototype clusters Ag14 (SR)6 and CO3 @Agm (SR)10 (R=isopropyl, cyclohexyl or tert-butyl; m=18 or 20) are employed to construct cluster-based metal-organic frameworks of different dimensions. In particular, both new ellipsoidal tetradecanuclear molecular cluster compounds, namely, Ag14 (S-iPr)6 (CO2 CF3 )8 ⋅(DMSO)6 (two polymorphic forms 1, 2) and [Ag14 (S-Cy)6 (CO2 CF3 )8 (DMSO)4 ]⋅(DMSO)3 (3), and a cluster-based metal-organic framework {Ag3 [Ag14 (S-iPr)6 (CO2 CF3 )11 (H2 O)3 CH3 OH]⋅(H2 O)2.5 }n (4) have been isolated and structurally characterized. Furthermore, increased acidity of the reaction mixture afforded three carboxylate-templated cluster based frameworks: a chain-like compound {[HN(CH3 )2 CO]⋅[CO3 @Ag18 (S-tBu)10 (NO3 )7 (DMF)4 ]⋅DMF}n (5), as well as two layer-type compounds, namely, {Ag[CO3 @Ag20 (S-iPr)10 (CO2 CF3 )9 (CO2 HCF3 )(CH3 OH)2 ]}n (6) and {Ag2 [CO3 @Ag20 (S-Cy)10 (CO2 CF3 )10 (CO2 HCF3 )2 (H2 O)2 ]⋅(H2 O)3 ⋅(CH3 OH)3 }n (7) exhibiting sql-net characteristics. It is demonstrated that the C≡C2- pre-template, which draws several Ag+ ions together to form the C2 @Agn entity, plays an indispensable role in the syntheses of these compounds. Furthermore, covalent linkage of these nano-sized silver thiolate clusters from one- to three-dimensions revealed enormous potential for the future development of silver cluster-based frameworks.

Vanadium and Chromium Molecular Cluster Batteries (MCB): Li- Storage in Transition Metal Complexes

Increasing energy demands and the requirement to reduce carbon dioxide emissions at the same time accelerated the world-wide research on renewable energy sources and energy storage. However, for future applications in personal electronics, electro-mobility and decentralised energy storage, new LIB electrode materials based on light-weight and earth abundant components with superior redox activity, long-term stability and high energy density are urgently required. The concept of using molecular transition metal clusters as active electrode materials for reversible Li ion shuttling opens up a new direction for energy storage.[1] These metal complexes are interesting electrode materials due to the ability of the transition metal ions to exist in several oxidation states and reversibly reacting with Li.[2,3] In this study we introduce LIBs based on molecular cluster systems of the early transition metal ions vanadium and chromium as the cathode active material, in a so-called molecular cluster battery (MCB). Transition metal complexes of different ligand systems were characterised by IR, XRD and SEM techniques. Their Li cycling behaviour was investigated by galvanostatic cycling and cyclic voltammetry (CV). High reversible specific capacities with low capacity loss were found and multi-step redox processes were observed reflecting the various oxidation states of these metal ions. The 2D channels of the crystalline compounds, which are revealed in their crystal packing diagram, are suitable for an easy Li ion transportation trough the structure. The Li ion diffusion coefficients were determined by various electrochemical techniques, such as GITT, CV and EIS to understand the Li ion kinetics of these molecular metal clusters. The various oxidation steps of molecular cluster compounds allow multi-step redox changes making these materials interesting compounds with potentially high specific capacities and allow a study of the kinetics of the lithium ion diffusion pathway.

Investigation on the photoconductivity of polyoxometalates

The Keggin-type tungsten-series polyoxometalates photoconductivities and gas sensing performance for ethanol.

Catalytic Oxygen Evolution by Cobalt Oxido Thin Films.

The contemporary demand to generate fuels from solar energy has stimulated intense effort to develop water splitting catalysts that can be coupled to light-absorbing materials. Cobalt oxido catalyst (Co-OECs) films deposited from buffered Co(II) solutions have emerged as arguably the most studied class of heterogeneous oxygen evolution catalysts. The interest in these materials stems from their formation by self-assembly, their self-healing properties, and their promising catalytic activity under a variety of conditions. The structure and function of these catalysts are reviewed here together with studies of molecular Co-O cluster compounds, which have proven invaluable in elucidating the chemistry of the Co-OECs.

N,N′-Fused Bisphosphole: Heteroaromatic Molecule with Two-Coordinate and Formally Divalent Phosphorus. Synthesis, Electronic Structure, and Chemical Properties

The reduction of 6,12-dichloro-1,2,3,4,7,8,9,10-octahydro-6H,12H-[1,2,3]benzodiazaphospholo[2,1-a][1,2,3]benzodiazaphosphole (3) by metallic magnesium in tetrahydrofuran (THF) affords the N,N'-fused bisphosphole 1 in 92% yield. The compound reveals a novel type of 10π-electron heteroaromatic system [NICS(0) = -11.4], containing a two-coordinate and formally divalent phosphorus atom. Compound 1 possesses a much higher coordination activity than many other diazaphospholes. This is caused by a novel type of complexation to a metal ion wherein the lone phosphorus pairs are not involved in metal coordination. Instead, the 10π-electron heteroaromatic system provides two electrons for P → M bond formation. Polarization of the ligand results in the formation of extended molecular associates or cluster compounds. Complexes of 1 with mercury dichloride [{(1)3HgCl}2(μ6-Cl)](+)Cl(-) (7) and tin dichlorides [1·SnCl2(PhMe solvate)] (8a) and [1·SnCl2] (8b) are, in fact, supramolecular in nature, containing multiple intermolecular short contacts. Crystals of complex 8a containing short Sn···Sn packing interactions were converted reversibly to metallic tin after workup with THF. The simple mixing of 1 and 3 (1:1) gave a P-P bridging dimeric species prone to easy dissociation. The addition of GeCl2(diox) to the equimolar mixture of 1 and 3 shifted the equilibrium to the formation of a poorly soluble salt-like dimer 6, which is, in fact, a stacked 18π-electron dication having a through-space delocalization of π electrons.

ChemInform Abstract: Chemical and Photochemical Functionality of the First Molecular Bismuth Vanadium Oxide.

AbstractThe first molecular bismuth vanadium oxide cluster compound H3 [{Bi(dmso)3}4V13O40] ·≈4DMSO is synthesized by addition of an aqueous Bu4NOH solution to a hot solution of Bi(NO3)3 and (Bu4N)3[H3V10O28] in DMSO/2% H2O (80 °C, 1 h, 91% yield).

Hexatellurium Rings in Coordination Polymers and Molecular Clusters: Synthesis and Crystal Structures of [M(Te6)]X3 (M = Rh, Ir; X = Cl, Br, I) and [Ru2(Te6)](TeBr3)4(TeBr2)2

AbstractThe reaction of an electron‐rich transition metal M (M = Ru, Rh, Ir), tellurium and TeX4 (X = Cl, Br, I) resulted in black crystals of five ternary coordination polymers with the general composition [MIII(Te6)]X3 (M = Rh, Ir) and of the molecular cluster compound [RuII2(Te6)](TeIIBr3)4(TeIIBr2)2. X‐ray diffraction on single‐crystals revealed that the compounds [M(Te6)]X3 crystallize isostructurally in the trigonal space group type R$\bar{3}$c. In their crystal structures linear, positively charged [MIII(Te6)] chains form the motif of a hexagonal rod packing. In the chain, each of the formally uncharged Te6 molecules with chair conformation acts as a bis‐tridentate bridging ligand to two M atoms. The octahedrally coordinated M atoms are spiro atoms in the chain of trans vertices sharing heterocubane fragments. Including the isolated halide ions, which provide charge balance, the entire arrangement resembles a cut‐out of the α‐polonium structure type.In the monoclinic compound Ru2Te12Br16 (space group P21/n), the ruthenium atoms of the hetero‐cubane core of the molecular cluster [Ru2(Te6)](TeBr3)4(TeBr2)2 are saturated by terminal bromidotellurate(II) groups. Again, the Te6 ring is formally uncharged. With the tellurium atoms acting as electron‐pair donors the 18 electron rule is fulfilled for the M atoms in all compounds.

The preparation of metal oxygen molecular cluster embedded organic–inorganic nanocomposite and its rectification behaviour

Abstract A metal oxygen molecular cluster compound has been utilized for the preparation of organic–inorganic nanocomposite film by a sol–gel method. The entrapment of these cluster compounds in a composite film has been characterized by various physico-chemical techniques. The entrapped metal oxygen cluster stabilizes its energy levels, which is evidenced from the change in redox potential and band gap. The rectification phenomenon of composite films is attributed to the embedded cluster compounds. The rectification behaviour of the composite film, which is due to the charge transfer from molecular cluster and the electrode, has been studied.

Synthesis and Structure of [nPr3N(CH2)6NnPr3][CuFe3Br3(SePh)6], [Cu5Fe(SePh)7(PPh3)4] and [Cu4Fe3(SePh)10(PPh3)4

AbstractCuBr and Fe(OOCCH3)2 react with PhSeSiMe3 in acetonitrile in the presence of the diammonium salt [nPr3N(CH2)6NnPr3]Br2 to yield ionic [nPr3N(CH2)6NnPr3][CuFe3Br3(SePh)6]. The neutral complexes [Cu5Fe(SePh)7(PPh3)4] and [Cu4Fe3(SePh)10(PPh3)4] were obtained by similar reactions of different stoichiometric mixtures of CuOOCCH3 and FeCl2 with PPh3 and PhSeSiMe3. The crystal structures of the compounds were determined by single‐crystal X‐ray analysis to give new structural types of molecular cluster compounds formed by copper, iron and selenium. Thermal treatment of [Cu5Fe(SePh)7(PPh3)4] and [Cu4Fe3(SePh)10(PPh3)4] resultsin the formation of mixtures of binary Cu2Se and ternaryCuFeSe2.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Magnetic dipolar ordering and relaxation in the high-spin molecular cluster compoundMn6

Few examples of magnetic systems displaying a transition to pure dipolar magnetic order are known to date. As was recently shown, within the newly discovered class of single-molecule magnets, quite attractive examples of dipolar magnetism may be found. The molecular cluster spins and thus their dipolar interaction energy can be quite high, leading to reasonably accessible ordering temperatures even for sizable intercluster distances. In favorable cases bonding between clusters in the molecular crystal is by van der Waals forces only, and no exchange paths of importance can be distinguished. An important restriction, however, is the requirement of sufficiently low crystal field anisotropy for the cluster spin, in order to prevent the occurrence of superparamagnetic blocking at temperatures above the dipolar ordering transition. This condition can be met for molecular clusters of sufficiently high symmetry, as for the ${\mathrm{Mn}}_{6}$ molecular cluster compound studied here. The uniaxial anisotropy of the cluster spin $S=12$ is as small as $D∕{k}_{B}=0.013\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, giving a total zero-field splitting of the $S=12$ multiplet of $1.9\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. As a result, the electron-spin lattice relaxation time remains fast $(\ensuremath{\sim}{10}^{\ensuremath{-}4}\phantom{\rule{0.3em}{0ex}}\mathrm{s})$ down to ${T}_{\mathrm{c}}$ and no blocking occurs. Magnetic specific heat and susceptibility experiments show a transition to ferromagnetic dipolar order at ${T}_{\mathrm{c}}=0.16\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Classical Monte Carlo calculations, performed for Ising $S=12$ dipoles on a lattice do predict ferromagnetic ordering and account for the value of ${T}_{\mathrm{c}}$ as well as the shape of the observed specific heat anomaly. By applying magnetic fields up to $6\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ the hyperfine contributions ${C}_{\mathrm{hf}}$ to the specific heat arising from the $^{55}\mathrm{Mn}$ nuclei could be detected. From the time dependence of the measured ${C}_{\mathrm{hf}}$ the nuclear-spin lattice relaxation time ${T}_{1\mathrm{n}}$ could be determined for the same field range in the temperature region $0.2<T<0.6\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The nuclear magnetic relaxation was further studied by high field $^{55}\mathrm{Mn}$ pulse NMR measurements of both the nuclear ${T}_{1\mathrm{n}}$ and ${T}_{2\mathrm{n}}$ at $T=0.9\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ (up to $7\phantom{\rule{0.3em}{0ex}}\mathrm{T}$). The data are in good mutual agreement and can be well described by the theory for magnetic relaxation in highly polarized paramagnetic crystals and for dynamic nuclear polarization, which we extensively review. The experiments provide an interesting comparison with the recently investigated nuclear spin dynamics in the anisotropic single-molecule magnet ${\mathrm{Mn}}_{12}$-ac.

Superconductivity in a Molecular Metal Cluster Compound

Compelling evidence for band-type conductivity and even bulk superconductivity below Tc approximately 8 K has been found in (69,71)Ga NMR experiments in crystalline ordered, giant Ga84 cluster compounds. This material appears to represent the first realization of a theoretical model proposed by Friedel in 1992 for superconductivity in ordered arrays of weakly coupled, identical metal nanoparticles.

Cluster Approach to the Synthesis of Ternary Metal Sulfides: Molybdenum Disulfide Single Layers as a Precursor

The reactivity of negatively charged (MoS2)x− layers in aqueous single-layer dispersions resembles that of molecular Mo-S cluster compounds. These layers form covalent bonds with metal (M) cations (M=Cu, Ag, Pb, Cd, Hg, Pd), giving rise to ternary metal sulfides MzMoS2 whose Mo network contains direct Mo-Mo bonds.

Percolation and high-frequency hopping in cluster compounds and polymers

In strongly disordered solids the complex conductivity has a remarkably uniform dependence on the number of carriers, temperature and frequency. Still, as we illustrate for randomly packed molecular cluster compounds, it is possible to derive the relevant hopping parameters. In particular the analysis of the transition from phonon- to photon-assisted hopping in the pair limit, when combined with the low-frequency data, yields precise information. In polymer blends and conjugated polymers the charge mobility behaves in a qualitatively similar way, but its temperature and frequency dependences deviate from the almost universal behaviour in the fully random systems. We show how these differences relate to the mesoscopic structure.

Novel inorganic polymeric compounds based on the Re 4 chalcocyanide cluster complexes: synthesis and crystal structures of Mn 2[Re 4Se 4(CN) 12]·6H 2O, Cd 2[Re 4Te 4(CN) 12]·6H 2O, Cu 2[Re 4Te 4(CN) 12]·4H 2O and K 4Re 4Se 4(CN) 12·6H 2O

Three new tetrahedral rhenium chalcocyanide cluster compounds, Mn 2[Re 4Se 4(CN) 12]·6H 2O ( 1), Cd 2[Re 4Te 4(CN) 12]·6H 2O ( 2) and Cu 2[Re 4Te 4(CN) 12]·4H 2O ( 3), exhibiting polymeric structures have been synthesized by the treatment of molecular ionic cluster compounds K 4Re 4Q 4(CN) 12 (Q=Se, Te) with aqueous solutions of Mn(NO 3) 2, CdSO 4 and CuCl 2 in gel. The previously unknown starting compound K 4Re 4Se 4(CN) 12·6H 2O ( 4) was obtained by the reaction of Re 4Se 4(TeCl 2) 4Cl 8 with KCN in water. All four compounds have been characterized by single-crystal X-ray diffraction.