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A highly functionalized intermediate in the synthesis of Taxol has been synthesized, which features the tricyclic core and the required oxygen substituents at C1, C2, C7, C10, and C13. The key step, a ring-closing dienyne metathesis (RCDEYM) reaction, has been thoroughly optimized to favor the tricyclic product over the undesired bicyclic product resulting from diene metathesis. [ABSTRACT FROM AUTHOR]

Lacunary polyoxometalates of low nuclearity are difficult to synthesize in isolation. We report the facile synthesis of six {M2(B-β-SiW8O31)2} clusters (M = Co/Mn/Ni/Zn/Cu2+, Fe3+) that can be employed as building blocks for the formation of larger architectures. We show for the first time that such {B-β-SiW8O31} lacunae are capable of reorganizing into larger Keggin lacunary species even in the absence of an external source of tungstate. We hypothesize, based on electrospray ionization mass spectrometry evidence obtained, not only that such a transformation is only possible via an initial decomposition of the {SiW8} precursor into a {SiW6}-based intermediate but also that it is this {SiW6} species that acts as the template for the growth of the larger fragments. [ABSTRACT FROM AUTHOR]

The spectroscopic and photophysical properties of [Ru(bpy)3]2[[Mo18O54(SO3)2], where bpy is 2,2′-bipyridyl and [Mo18O54(SO3)2]4−is either the α or β-sulfite containing polyoxomolybdate isomer, have been measured and compared with those for the well known but structurally distinct sulfate analogue, α-[Mo18O54(SO4)2]4−. Electronic difference spectroscopy revealed the presence of new spectral features around 480 nm, although they are weak in comparison with the [Ru(bpy)3]2[Mo18O54(SO4)2] analogue. Surprisingly, Stern–Volmer plots of [Ru(bpy)3]2+luminescence quenching by the polyoxometallate revealed the presence of both static and dynamic quenching for both α and β-[Mo18O54(SO3)2]4−. The association constant inferred for the ion cluster [Ru(bpy)3]2α-[Mo18O54(SO4)2] is K= 5.9 ± 0.56 × 106and that for [Ru(bpy)3]2β-[Mo18O54(SO4)2] is K= 1.0 ± 0.09 × 107. Unlike the sulfate polyoxometalates, both sulfite polyoxometalate–ruthenium adducts are non-luminescent. Despite the strong electrostatic association in the adducts resonance Raman and photoelectrochemical studies suggests that unlike the sulfato polyoxometalate analogue there is no sensitization of the polyoxometalate photochemistry by the ruthenium centre for the sulfite anions. In addition, the adducts exhibit photochemical lability in acetonitrile, attributable to decomposition of the ruthenium complex, which has not been observed for other [Ru(bpy)3]2+-polyoxometalate adducts. These observations suggest that less electronic communication exists between the [Ru(bpy)3]2+and the sulfite polyoxoanions relative to their sulfate polyoxoanion counterparts, despite their structural and electronic analogy. The main distinction between sulfate and sulfite polyoxometalates lies in their reversible reduction potentials, which are more positive by approximately 100 mV for the sulfite anions. This suggests that the capacity for [Ru(bpy)3]2+or analogues to sensitize photoreduction in the adducts of polyoxometalates requires very sensitive redox tuning. [ABSTRACT FROM AUTHOR]

We have used Raman and IR spectroscopy to study the oxidation reaction of sulfite groups in the unique polyoxometalate compound K7Na[WVI18O56(SO3)2(H2O)2]·20H2O with a structure related to the Wells–Dawson type in situat high temperature and high pressure. The results give new insights into the unusual redox process that occurs in this compound with electrons and O2−ions transferred between the polyoxometalate cluster and SO32−/SO42−groups held within the cage in a process that has been termed the “Trojan Horse” effect. [ABSTRACT FROM AUTHOR]

We have used Raman and IR spectroscopy to study the oxidation reaction of sulfite groups in the unique polyoxometalate compound K7Na[WVI18O56(SO3)2(H2O)2]·20H2O with a structure related to the Wells–Dawson type in situat high temperature and high pressure. The results give new insights into the unusual redox process that occurs in this compound with electrons and O2−ions transferred between the polyoxometalate cluster and SO32−/SO42−groups held within the cage in a process that has been termed the “Trojan Horse” effect. [ABSTRACT FROM AUTHOR]

We have used Raman and IR spectroscopy to study the oxidation reaction of sulfite groups in the unique polyoxometalate compound K7Na[WVI18O56(SO3)2(H2O)2]·20H2O with a structure related to the Wells–Dawson type in situat high temperature and high pressure. The results give new insights into the unusual redox process that occurs in this compound with electrons and O2−ions transferred between the polyoxometalate cluster and SO32−/SO42−groups held within the cage in a process that has been termed the “Trojan Horse” effect. [ABSTRACT FROM AUTHOR]

We have used Raman and IR spectroscopy to study the oxidation reaction of sulfite groups in the unique polyoxometalate compound K7Na[WVI18O56(SO3)2(H2O)2]·20H2O with a structure related to the Wells–Dawson type in situat high temperature and high pressure. The results give new insights into the unusual redox process that occurs in this compound with electrons and O2−ions transferred between the polyoxometalate cluster and SO32−/SO42−groups held within the cage in a process that has been termed the “Trojan Horse” effect. [ABSTRACT FROM AUTHOR]

The Dawson-like polyoxometalate clusters (TEAH)6[H2W18O57(SO3)] (1) and (DMAH)8[W18O56(SO3)2(H2O)2] (2) were synthesized under similar reaction conditions by employing triethanolammonium (TEAH) and dimethylammonium (DMAH+) as cations, respectively. Crystallographic studies revealed that compound 1 has a compressed, peanut-like (W18) cage containing a single sulfite anion where each cage metal atom supports one terminal oxo-based ligand whereas compound 2 also has a (W18) cage, but tour of the eighteen cage metal atoms support two terminal oxo-based ligands with two sulfite anions embedded in the cluster. [ABSTRACT FROM AUTHOR]

The assembly of polyoxometalate architectures based on Mn-Anderson clusters capped with different aromatic platforms viathe ‘Tris’ linker (Tris = tris(hydroxymethyl)aminomethane), allows the formation and isolation of four new hybrid polyoxometalate clusters of 2–5with the general composition of [n-N(C4H9)4]3[MnMo6O18{(OCH2)3CN = CH-R}2]·solv., (R = –(C6H5) 2, –(C6H5O) 3, –(C11H8N) 4and –(C13H9) 5; solv. = MeOH or H2O). These compounds were obtained simply by the reaction of compound 1, ([n–N(C4H9)4]3[MnMo6O18{(OCH2)3CNH2}2]), with the corresponding aldehyde and the aromatic platforms were chosen to explore the design principles for covalently constructed POM aromatic–organic–inorganic hybrids. [ABSTRACT FROM AUTHOR]

Transition metal oxides exhibit a rich collection of electronic properties and have many practical applications in areas such as catalysis and ultra-high-density magnetic data storage. Therefore the development of switchable molecular transition metal oxides has potential for the engineering of single-molecule devices and nanoscale electronics. At present, the electronic properties of transition metal oxides can only be tailored through the irreversible introduction of dopant ions, modifying the electronic structure by either injecting electrons or core holes. Here we show that a molybdenum(VI) oxide ‘polyoxometalate’ molecular nanocluster containing two embedded redox agents is activated by a metallic surface and can reversibly interconvert between two electronic states. Upon thermal activation two electrons are ejected from the active sulphite anions and delocalized over the metal oxide cluster cage, switching it from a fully oxidized state to a two-electron reduced state along with the concomitant formation of an S–S bonding interaction between the two sulphur centres inside the cluster shell. [ABSTRACT FROM AUTHOR]

A family of polyoxometalates with the composition [H2V3M17O62]6– features a Dawson-like architecture containing two tetrahedral {VVO4} templates rather than main group hetero-anions ({PO4} or {SO4} etc.) typically associated with classical heteropolyacids, situated within a mixed-metal {MVI17VIVO54} cage and these clusters were first discovered using mass spectrometry. [ABSTRACT FROM AUTHOR]

The use of a ligand directed strategy in the assembly of discrete clusters, 1D chains, 2D layers, and 3D networks using aliphatic N-donor ligands has been investigated. The ligands are a family of amines with rigid backbones [cis, cis-1,3,5-triaminocyclohexane (cis-tach), cis, trans-1,3,5-triaminocyclohexane (trans-tach), cis-1,3-diaminocyclohexane (cis-tach), and cis-3,5-diaminopiperidine (cis-dapi)], and their complexation with Ag(I) salts results in a diverse set of architectures with the following compositions: [Ag3(cis-tach)2]F3·4CH3OH·O.5H2O (1), [Ag3(cis-tach)2]-F3·6H2O (2), {[Ag(cis-dach)]ClO4}n (3), {[Ag(cis-tach)]NO3}n (4), {[Ag(trans-tach)]PF6}n (5, and {[Ag(cis-dapi)]-CF3SO3}n (6). Structural analysis shows that compounds 1 and 2 are discrete M3L2 cage-type clusters with varying solvent molecule content. Short Ag…Ag contacts (3.021 (8) Å) are observed to dimerize discrete units in compound 2. Compound 3 is a 1D zigzag chain formed by coordination to the two primary amines of cis-dach, whereas the tridentate ligands in compounds 4 and 5 (cis-tach and trans-tach, respectively) are able to form tubular architectures by virtue of their ability to ‘wrap’ round the channel walls. An infinite 2D coordination network is demonstrated by compound 6, in which the three coplanar amino donors of cis-dapi coordinate to the trigonal planar Ag(I) ions to form a layered structure of 63 topology. These are compared with a previously reported 3D structure, {[Ag(trans-tach)]NO3}n (7), that belongs to this family of architectures. [ABSTRACT FROM AUTHOR]

The unsymmetrical Mn-Anderson polyoxometalate cluster, [N(C4-H9)4]3[MnMo6O18(C4H6O3NO2)(C4H6O3NH2)] (1; N(C4H9)4+ = TBA+), has been prepared and characterized by X-ray crystallography and electrospray ionization mass spectrometry (ESI-MS). Covalent functionalization of compound 1 leads to the controlled assemblies of unsymmetrical alkoxopolyoxometalate clusters of compounds 2–5, which can be directly observed in solution as revealed by ESI-MS studies. [ABSTRACT FROM AUTHOR]

The article presents a study on the use of mass spectrometry in the study of polyoxometalates solutions. It mentions that the determination of the structures of polyoxometalate clusters has remained a problem due to the complexities of protonation states. The study uses mass spectrometry to determine the degree of protonation and number of heteroanions in polyoxometalates solutions. An overview of the study is provided.

A nanoscale FeIII-substituted polyoxotungstate [KFe12(OH)18(α-1,2,3-P2W15O56)4]29− is synthesized starting from the trilacunary {P2W15} Dawson cluster and [Fe3(μ3-O)(CH2=CHCOO)6(H2O)3]1+ to give a 2.6 nm tetrahedral cluster species and the 16 kDa cluster can be directly observed in solution as revealed by mass spectrometry studies. [ABSTRACT FROM AUTHOR]

A chiral heteropolyoxometalate-based framework, synthesised using a planar aromatic tri-acid included as a guest, contains partially filled 1D channels and exhibits reversible water sorption capabilities. [ABSTRACT FROM AUTHOR]

Investigates lanthanum coordination networks based on unusual five-connected topologies. Design and construction of inorganic coordination networks; Flexibility of the coordination sphere of lanthanide ions; Preparation of noninterpenetrating frameworks with large internal cavities.

The incorporation of polyoxometalates (POMs) as structural units into ordered porous constructs such as metal-organic frameworks (MOFs) is desirable for a range of applications where intrinsic properties inherited from both the MOF and POM are utilized, including catalysis and magnetic data storage. The controlled self-assembly of targeted MOF topologies containing POM units is hampered by the wide range of oxo and hydroxo units on the peripheries of POMs that can act as coordinating groups toward linking metal cations leading to a diverse range of structures, but incorporation of organic donor units into hybrid POMs offers an alternative methodology to programmably synthesize POM/MOF conjugates. Herein, we report six coordination polymers obtained serendipitously wherein Zn2+ and Cu2+ link pyridine-appended Mn-Anderson clusters into two- and three-dimensional network solids with complex connectivities and topologies. Careful inspection of their solid-state structures has allowed us to identify common structure-directing features across these coordination polymers, including a square motif where two Zn2+ cations bridge two POMs. By correlating certain structural motifs with synthetic conditions, we have formulated a series of design considerations for the self-assembly of coordination polymers of hybrid POMs, encompassing the selection of reaction conditions, coligands, and linking metal cations. We anticipate that these synthetic guidelines will inform the future assembly of hybrid POMs into functional MOF materials. [ABSTRACT FROM AUTHOR]

Understanding the process of the self-assembly of gigantic polyoxometalates and their subsequent molecular growth, by the addition of capping moieties onto the oxo-frameworks, is critical for the development of the designed assembly of complex high-nuclearity cluster species, yet such processes remain far from being understood. Herein we describe the molecular growth from {Mo150} and {Mo120Ce6} to afford two half-closed gigantic molybdenum blue clusters {Mo180} (1) and {Mo130Ce6} (2), respectively. Compound 1 features a hat-shaped structure with the parent wheel-shaped {Mo150} being capped by a {Mo30} unit on one side. Similarly, 2 exhibits an elliptical lanthanide-doped wheel {Mo120Ce6} that is sealed by a {Mo10} unit on one side. Moreover, the observation of the parent uncapped {Mo150} and {Mo120Ce6} clusters as minor products during the synthesis of 1 and 2 strongly suggests that the molecular growth process can be initialized from {Mo150} and {Mo120Ce6} in solution, respectively. [ABSTRACT FROM AUTHOR]

By using solubility control to crystallize the prenucleation clusters of hydrosol, a family of titanium-oxo clusters possessing the {Ti18O27} core in which the 18 Ti(IV)-ions are uniquely connected with µ-oxo ligands into a triple-decked pentagonal prism was obtained. The cluster cores are wrapped by external sulfate and aqua ligands, showing good solubilities and stabilities in a variety of solvents including acetonitrile and water and allowing their solution chemistry being studied by means of electrospray ionization mass spectroscopy, 17O NMR, and vibrational spectroscopy. Furthermore, this study provides new titanium oxide candidates for surface modifications and homogeneous photocatalysis. [ABSTRACT FROM AUTHOR]

Stable phenalenyl radicals have great potential as the basis for new materials for applications in the field of molecular electronics. In particular, electronically stabilized phenalenyl species that do not require steric shielding are molecules of fundamental interest, but are notoriously difficult to synthesize. Herein, the synthesis and characterization of two phenalenyl-type cations is reported: planar benzo[i]naphtho[2,1,8-mna]xanthenium (8+) and helical benzo[a]naphtho[8,1,2-jkl]xanthenium (9+), which can be reduced to the corresponding radicals. Radical 9 represents the first stable, helical phenalenyl radical which does not rely on bulky substituents to ensure its stability. Both cations are water-soluble, and the radicals are stable for weeks at room temperature under air. These compounds were characterized crystallographically, and also by NMR, EPR, electrochemistry, and electronic spectra. The synthesis of the previously reported compound benzo[5,6]naphthaceno[1,12,11,10-jklmna]xanthylium (5+), the largest oxygen-containing polycyclic hydrocarbon, was undertaken for comparison with 8+ and 9+, allowing us to report its crystal structure here for the first time. The different properties of these compounds and their radicals are explained by considering their differing aromaticities using in-depth computational methods. [ABSTRACT FROM AUTHOR]

A series of tripodal alcohols substituted Anderson-type polyoxometalates (POMs) including mono-substituted (compounds 1 and 2), asymmetrical bi-substituted (compound 3), and symmetrical bi-substituted ones (compounds 4 and 5) have been synthesized under hydrothermal conditions using a pre-designed step-by-step strategy, and compounds 1, 2 and 4 have been fully characterized by single-crystal X-ray diffraction, ESI-MS, and elemental analysis. [ABSTRACT FROM AUTHOR]

Two nanosized 2.6 nm FeIII substituted polyoxotungstates [FeIII13P8W60O227(OH)15(H2O)2]30- (1) and [FeIII13P8W60O224(OH)12(PO4)4]33- (2) are presented herein. Both clusters are synthesized from the reactions of trilacunary polyoxotungstate precursor [α-P2W15O56]12- and FeCl3 under strict pH control at atmospheric pressure. The compounds are fully characterised in the solid state (FTIR and single-crystal XRD, elemental and thermogravimetric analyses), solution (cyclic voltammetry and UV-Vis spectroscopy) and in the gas phase (ESI-MS). An {FeIII 13} core is present in both clusters which can be described as Archimedean solids (truncated tetrahedron, 1; elongated cuboctahedron, 2). 1 shows iron delivery properties coupled to a K+-triggered transformation of the {Fe13} core to a {K-Fe12} core in solution. Cyclic voltammetry shows the presence of independent W- and Fe-centred redox processes that support the stability of the clusters in solution. ESI-MS analyses confirm further the stability of 1 and 2 in the gas phase. [ABSTRACT FROM AUTHOR]

Enamides, dienamides, and enynamides are important building blocks in synthetic, biological, and medicinal chemistry as well as materials science. Despite the extensive breath of their potential utility in synthetic chemistry, there is a lack of simple, high-yielding methods to deliver them efficiently and as single isomers. In this paper, we present a novel, protecting group free, efficient, and stereoselective approach to the generation of β-halo-enamides. The methodology presented provides a robust synthetic platform from which E- or Z-enamides can be generated in good yields and with complete stereocontrol. [ABSTRACT FROM AUTHOR]

The inorganic host-guest complex Na22{[MoVI36O112·(H2O)16]⊂[MoVI130MoV20O442(OH)10(H2O)61]}·180H2O ≡ {Mo36}⊂{Mo150}, compound 1, has been isolated in its solid crystalline state via unconventional synthesis in a custom flow reactor. Carrying out the reaction under controlled flow conditions selected for the generation of {Mo36}⊂{Mo150} as the major product, allowing it to be reproducibly isolated in a moderate yield, as opposed to traditional "one-pot" batch syntheses that typically lead to crystallization of the {Mo36} and {Mo150} species separately. Structural and spectroscopic studies of compound 1 and the archetypal Molybdenum Blue (MB) wheel, {Mo150}, identified compound 1 as a likely intermediate in the {Mo36} templated synthesis of MB wheels. Further evidence illustrating the template effect of {Mo36} to MB wheel synthesis was indicated by an increase in the yield and rate of production of {Mo150} as a direct result of the addition of preformed {Mo36} to the reaction mixture. Dynamic light scattering (DLS) techniques were also used to corroborate the mechanism of formation of the MB wheels through observation of the individual cluster species in solution. DLS measurement of the reaction solutions from which {Mo36} and {Mo150} crystallized gave particle size distribution curves averaging 1.9 and 3.9 nm, consistent with the dimensions of the discrete clusters, which allowed the use of size as a possible distinguishing feature of these key species in the reduced acidified molybdate solutions and to observe the templation of the MB wheel by {Mo36} directly. [ABSTRACT FROM AUTHOR]

Vanadate(V)-templated Dawson-type capsules {VIVMVI17(VO4)2} (M = Mo, W; 1-2) have been synthesized and investigated by electrochemical methods in aqueous and organic media using spectroscopic techniques, EPR, UV-vis/NIR, IR, and CSI-MS (cryospray ionization mass spec.), and the clusters have been examined in the solid state by magnetic studies. The collision-induced dissociation (CID-MS) studies confirmed the solution structures as well as helped pinpoint the position of the vanadium ion on the {VM17}-type shell, which was corroborated by EPR and theoretical studies. [ABSTRACT FROM AUTHOR]

Four transition metal incorporated phosphotungstates have been synthesized through the reaction of Na2WO4, H3PO4, Co/Ni(NO3)2, and the multifunctional amine N,N'-Bis(2-hydroxyethyl) piperazine (bhep). Na2{MHbhep(H2O)4}[PW10M2O38{Hbhep}2] M = Co2+ (1), and Ni2+(2) represent rare examples of complete transition metal chelate encapsulation within a Keggin polyanion. Slight modification of the reaction procedure yielding 1 also yields the two dimensional material (H2bhep)3Na4[CO4(H2O)2(PW9O34)2]·15H2O (3). Finally, the isolation of a phosphotungstate cluster containing 18 Co2+ ions is achieved through the bridging of two [Co9(OH)3(H2O)6(HPO4)2(B-α-PW9O34)3]16- clusters by the bhep ligand to form the [{Co9(OH)3(H2O)3(HPO4)2(B-α-PW9O34)3}2 {C8H18N2O2}3]32- dimer (4). The dimerisation process is achieved via the monodentate coordination of the hydroxyl groups from three bhep ligands to each polyanion by displacing the water ligands typically found coordinated to the {Co9} core forming a nanoscale cylinder-like capsule capped by two {Co9P5W27} with three BHEP-based ligand spacers. [ABSTRACT FROM AUTHOR]

Four transition metal incorporated phosphotungstates have been synthesized through the reaction of Na2WO4, H3PO4, Co/Ni(NO3)2, and the multifunctional amine N,N′-Bis(2-hydroxyethyl) piperazine (bhep). Na2{MHbhep(H2O)4}[PW10M2O38{Hbhep}2] M = Co2+(1), and Ni2+(2) represent rare examples of complete transition metal chelate encapsulation within a Keggin polyanion. Slight modification of the reaction procedure yielding 1also yields the two dimensional material (H2bhep)3Na4[Co4(H2O)2(PW9O34)2].15H2O (3). Finally, the isolation of a phosphotungstate cluster containing 18 Co2+ions is achieved through the bridging of two [Co9(OH)3(H2O)6(HPO4)2(B-α-PW9O34)3]16−clusters by the bhep ligand to form the [{Co9(OH)3(H2O)3(HPO4)2(B-α-PW9O34)3}2{C8H18N2O2}3]32−dimer (4). The dimerisation process is achieved viathe monodentate coordination of the hydroxyl groups from three bhep ligands to each polyanion by displacing the water ligands typically found coordinated to the {Co9} core forming a nanoscale cylinder-like capsule capped by two {Co9P5W27} with three BHEP-based ligand spacers. [ABSTRACT FROM AUTHOR]

The compositional parameter space in the formation of polynuclear clusters is probed in the synthesis of a series of dodecanuclear coordination clusters of NiII and CoII with isostructural D3h-symmetric frameworks. At the core of their construction are a carbonate template and the directing ligands cis,trans-1 ,3,5-triaminocycIohexane and acetate at contrasting pH values. The pH and stoichiometric dependence has been mapped, and analysis by electrospray mass spectrometry reveals the cluster cores in solution. In two specific cases, site-specific occupations are eluded to by analysis of the magnetic properties, and we discuss the possibility of controlling the molecular composition of mixed metal polynuclear clusters. [ABSTRACT FROM AUTHOR]

We present two new ligands, 2,3-dihydro-1-(2-pyridyl-methyl)-imidazo[1,2-f]phenanthridinium bromide (L1·Br) and 2,3-dihydro-1-(4-pyridyl-methyl)-imidazo[1,2-f]phenanthridinium bromide (L2·Br), which have been synthesized and fully characterized as coordinating cations. The reactions of Cu(BF4)2 (compound 1), Cu(NO3)2 (compound 2), CuBr2 (compound 3), Cu(NO3)2 and NaN3 (compound 4), Cu(NO3)2 and NaSCN (compound 5) with L1·Br and CuBr2 with L2·Br (compound 6) have been carried out. The crystal structures of the resulting metal–organic assemblies have been determined and the intermolecular interactions of the compounds in the crystalline phase have been analysed. A mononuclear copper(II) compound has been obtained with CuBr2, in which the copper(II) ion adopts a tetrahedral geometry with a CuNBr3 coordination motif. With Cu(BF4)2, two L1+ cations and two bromide anions chelate the copper ion giving a CuN2Br2 motif, while the BF4− is present as a non-coordinating counterion. With Cu(NO3)2, a five coordinated copper complex is obtained whereas when bridging ligands such as NaN3 and NaSCN are added into the reaction mixture of L1·Br and Cu(NO3)2, two novel dinuclear copper coordination cores of [Cu2(μ1,1-N3)2(N3)4]2− and Cu(CH3O)2(SCN)4]2− form. The presence of the large heteroaromatic cationic DIP moiety within the ligand system leads to the formation of 1-, 2- and 3-D supramolecular arrays based on the interactions of the π systems between adjacent molecules. [ABSTRACT FROM AUTHOR]

The use of a strategy combining ligand design and changes of reaction conditions has been investigated with the goal of directing the assembly of mononuclear, dinuclear, tetranuclear, and polymeric copper(ll) complexes. As a result, closely related copper monomers, alkoxo dimers, and hydroxo cubanes, along with a carbonate-bridged polymeric species, have been synthesized using the rigid, aliphatic amino ligands cis-3,5-diamino-trans-hydroxycyclohexane (DAHC), cis-3,5-diamino-trans-methoxycyclohexane (DAMC), and the glutaryl-linked derivative glutaric acid bis-(cis-3,5-diaminocyclohexyl) ester (GADACE). The composition of the monomeric complex has been determined by X-ray crystallography as [Cu(DAHC)2}(CIO4)2 (1), the two dimers as [{Cu(DAHC)(OMe)}2]· (CIO4)2·MeOH (2) and [{Cu(DAMC)(OMe)(CIO4}2] (3), the three Cu4O4 cubanes as [fCu(DAHC)(OH)}4}(CIO4)4· 2.5MeOH (4), ({Cu(DAMC)(OH)}4](ClO4)4·H2O (5), and [{Cu2(OH)2(GADACE)}2]Cl4³2MeOH³6H2O (6), and an infinite-chain structure as [{Cu(DAHC)(CO3)}n] (7). Furthermore, the cubane structures 4 and 5 have been investigated magnetically. Our studies indicate that formation of the monomeric, dimeric, and tetranuclear DAHC and DAMC complexes can be controlled by small changes in reaction conditions and that further preorganization of the ligand moiety by linking the DAHC cores (GADACE) allows more effective direction of the self-assembly of the Cu4O4 cubane core. [ABSTRACT FROM AUTHOR]

Here we show how a simple inorganic salt can spontaneously form autocatalytic sets of replicating inorganic molecules that work via molecular recognition based on the {PMo12} ≡ [PMo12O40] 3– Keggin ion, and {Mo36} ≡ [H3Mo57M6(NO)6O183(H2O)18] 22– cluster. These small clusters are able to catalyze their own formation via an autocatalytic network, which subsequently template the assembly of gigantic molybdenum-blue wheel {Mo154} ≡ [Mo154O462H14(H2O)70] 14–, {Mo132} ≡ [MoVI 72MoV 60O372(CH3COO)30(H2O)72] 42– ball-shaped species containing 154 and 132 molybdenum atoms, and a {PMo12}⊂{Mo124Ce4} ≡ [H16MoVI 100MoV 24Ce4O376(H2O)56 (PMoVI 10MoV 2O40)(C6H12N2O4S2)4] 5– nanostructure. Kinetic investigations revealed key traits of autocatalytic systems including molecular recognition and kinetic saturation. A stochastic model confirms the presence of an autocatalytic network involving molecular recognition and assembly processes, where the larger clusters are the only products stabilized by the cycle, isolated due to a critical transition in the network. [ABSTRACT FROM AUTHOR]

Three discrete cobalt-substituted silicotungstates, [Co3(H2O)(B-β-SiW9O34)(B-β-SiW8O29(OH)2)]12− (1), [Co3(H2O)(B-α-SiW9O34)(B-β-SiW8O31)]14− (2), and [Co9Cl2(OH)3(H2O)9(B-β-SiW8O31)3]17− (3), have been synthesized using a synthetic approach involving Co(ii) ions, the dilacunary [γ-SiW10O36]8− polyanion and a bulky organic cation in basic media; all three compounds have been fully characterized and their position as structural intermediates in Co-containing silicotungstate chemistry is described. [ABSTRACT FROM AUTHOR]

Assembly of an unprecedented [(PVMnIIWVI11O39)2{PVO4}]13− and a [P2Mn4W18O68]10− cluster have been observed and structurally characterised and cryospray mass spectroscopic ionization (CSI) has been used to observe one of the very reactive building blocks linking solid state with solution studies. [ABSTRACT FROM AUTHOR]

Heteroanion (HA) moieties have a key role in templating of heteropolyoxometalate (HPA) architectures, but clusters templated by two different templates are rarely reported. Herein, we show how a cross-shaped HPA-based architecture can self-sort the HA templates by pairing two different guests into a divacant {XYW15O54} building block, with four of these building block units being linked together to complete the cross-shaped architecture. We exploited this observation to incorporate HA templates into well-defined positions within the clusters, leading to the isolation of a collection of mixed-HA templated cross-shaped polyanions [(XYW15O[sub 54])[sub 4](WO[sub 2])[sub 4]][sup 32-/36-] (X = H-P, Y = Se, Te, As). The template positions have been unambiguously determined by single crystal X-ray diffraction, NMR spectroscopy, and high-resolution electrospray ionization mass spectrometry; these studies demonstrated that the mixed template containing HPA clusters are the preferred products which crystallize from the solution. Theoretical studies using DFT calculations suggest that the selective self-sorting originates from the coordination of the template in solution. The cross-shaped polyoxometalate clusters are redox-active, and the ability of molecules to accept electrons is slightly modulated by the HA incorporated as shown by differential pulse voltammetry experiments. These results indicate that the cross-shaped HPAs can be used to select templates from solution, and themselves have interesting geometries, which will be useful in developing functional molecular architectures based upon HPAs with well-defined structures and electronic properties. [ABSTRACT FROM AUTHOR]

We describe why the cyclic heteropolyanion [P8W48O184]40- (abbreviated as {P8W48}) is an ideal building block for the construction of intrinsically porous framework materials by classifying and analyzing >30 coordination polymers incorporating this polyoxometalate (POM) ligand. This analysis shows that the exocyclic coordination of first-row transition metals (TMs) to {P8W48} typically yields frameworks which extend through {W-O-TM-O-W} bridges in one, two, or three dimensions. However, despite the rich structural diversity of such compounds, the coordination of TMs to the {P8W48} ring is poorly understood, and therefore largely unpredictable, and had not until now been present with any structural classification that could allow rational design. Herein, not only do we present a new approach to understand and classify this new class of materials, we also present three {P8W48}-based frameworks which complement those frameworks which have previously been described. These new compounds help us postulate a new taxonomy of these materials. This is possible because the TM coordination sites of the {P8W48} ring are found, once fully mapped, to lead to well-defined classes of connectivity. Together, analysis provides insight into the nature of the building block connectivity within each framework, to facilitate comparisons between related structures, and to fundamentally unite this family of compounds. Hence we have tentatively named these compounds as "POMzites" to reflect the POM-based composition and zeolitic nature of each family member, although crucially, POMzites differ from zeolites in the modular manner of their preparation. As the synthesis of further POMzites is anticipated, the classification system and terminology introduced here will allow new compounds to be categorized and understood in the context of the established materials. A better understanding of TM coordination to the {P8W48} ring may allow the targeted synthesis of new frameworks rather than the reliance on serendipity apparent in current methods. [ABSTRACT FROM AUTHOR]

We report an approach to synthesize molecular tungsten-oxide-based pentagonal building blocks, in a new {W21O72} unit, and show how this leads to a family of gigantic molecular architectures including [H12W48O164]28− {W48}, [H20W56O190]24− {W56}, and [H12W92O311]58− {W92}. The {W48} and {W56} clusters are both dimeric species incorporating two {W21} units and the {W56} species is the first example of a molecular metal oxide cluster containing a chiral “double-stranded” motif which is stable in solution as confirmed by mass spectrometry. The {W92} anion having four {W21} units is one of the largest transition metal substituted isopolyoxotungstates known. [ABSTRACT FROM AUTHOR]

The article presents a research study which aims to develop new types of Polyoxometalates (POM)-based micropatterned surfaces for biomolecule or cell interactions. The study establishes a deeper understanding of the mechanisms driving the cell adhesion behavior of the interactions between POM and self-assembled monolayers (SAMs). It adjusts the functional groups at the tails of SAMs and applying novel polyoxometalate clusters into SAMs.

We describe the synthesis, structure, self-assembly, solution chemistry, and mass spectrometry of two new gigantic decameric molybdenum blue wheels, {Mo200Ce12} (1) and {Mo100Ce6} (2), by building block rearrangement of the tetradecameric {Mo154} framework archetype and control of the architecture’s curvature in solution from the addition of Ce(III). The assembly of 1 and 2 could be directed accordingly by adjusting the ionic strength and acidity of the reaction mixture. Alternatively, the dimeric cluster {Mo200Ce12} could be transformed directly to the monomeric species {Mo100Ce6} upon addition of a potassium salt. ESI-ion mobility mass spectra were successfully obtained for both {Mo200Ce12} and {Mo100Ce6}, which is the first report in molybdenum blue chemistry thereby confirming that the gigantic clusters are stable in solution and that ion mobility measurements can be used to characterize nanoscale inorganic molecules. [ABSTRACT FROM AUTHOR]

Molecular self-assembly has often been suggested as the ultimate route for the bottom-up construction of building blocks atom-by-atom for functional nanotechnology, yet structural design or prediction of nanomolecular assemblies is still far from reach. Whereas nature uses complex machinery such as the ribosome, chemists use painstakingly engineered step-by-step approaches to build complex molecules but the size and complexity of such molecules, not to mention the accessible yields, can be limited. Herein we present the discovery of a palladium oxometalate {Pd84}-ring cluster 3.3 nm in diameter; {Pd84042(OAc)28(P04)42]70- ({Pd84} = {Pd12)7},) that is formed in water just by mixing two reagents at room temperature, giving crystals of the compound in just a few days. The structure of the {Pd84}-ring has sevenfold symmetry, comprises 196 building blocks, and we also show, using mass spectrometry, that a large library of other related nanostructures is present in solution. Finally, by analysis of the symmetry and the building block library that construct the {Pd84} we show that the correlation of the symmetry, subunit number, and overall cluster nuclearity can be used as a "Rosetta Stone" to rationalize the "magic numbers" defining a number of other systems. This is because the discovery of {Pd84} allows the relationship between seemingly unrelated families of molecular inorganic nanosystems to be decoded from the overall cluster magic-number nuclearity, to the symmetry and building blocks that define such structures allowing the prediction of other members of these nanocluster families. [ABSTRACT FROM AUTHOR]

Using [Mo2S2O2(H2O)6]2+ and squarate dianion, we synthesized the thiometalate ring compounds [(Mo2S2O2)x(OH),(C4O4)z(Mo2O8)o(H2O)p]n-, where [x,y,z,o,p,n] = [7,14,2,0,2,4] for 1, [6,8,2,2,4,8] for 2, and [4,6,1,1,0,4] for both 3a and 3b, which are chiral and nonchiral isomers, respectively. Not only do the four thiometalate clusters show decreasing symmetry at the molecular level across the series, but the incorporation of the "addendum" {Mo2O8}o, unit also allows the thiome- talate ring to twist. The reaction initially yields the chiral molecule 3a with a twisted ring, which undergoes spontaneous resolution upon crystallization; the reaction mixture later yields the intrinsically nonchiral isomer 3b with a nontwisted ring. In addition, the compounds are able to promote the electrocatalytic evolution of hydrogen. [ABSTRACT FROM AUTHOR]

The process of osmotically driven crystal morphogenesis of polyoxometalate (POM)-based crystals is investigated, whereby the transformation results in the growth of micrometer-scale tubes 10-100 μm in diameter and many thousands of micrometers long. This process initiates when the crystals are immersed in aqueous solutions containing large cations and is governed by the solubility of the parent POM crystal. Evidence is presented that indicates the process is general to all types of POMs, with solubility of the parent crystal being the deciding parameter. A modular approach is adopted since different POM precursor crystals can form tubular architectures with a range of large cationic species, producing an ion-exchanged material that combines the large added cations and the large POM-based anions. It is also shown that the process of morphogenesis is electrostatically driven by the aggregation of anionic metal oxides with the dissolved cations. This leads to the formation of a semi-permeable membrane around the crystal. The osmotically driven ingress of water leads to an increase in pressure, and ultimately rupture of the membrane occurs, allowing a saturated solution of the POM to escape and leading to the formation of a "self-growing" microtube in the presence of the cation. It is demonstrated that the growth process is sustained by the osmotic pressure within the membrane surrounding the parent crystal, as tube growth ceases whenever this pressure is relieved. Not only is the potential of the modular approach revealed by the fact that the microtubes retain the properties of their component parts, but it is also possible to control the direction of growth and tube diameter. In addition, the solubility limits of tube growth are explored and translated into a predictive methodology for the fabrication of tubular architectures with predefined physical properties, opening the way for real applications. [ABSTRACT FROM AUTHOR]

Two polyoxometalate open framework (POMOF) materials have been synthesized using a secondary building unit (SBU) approach that facilitates the convergent assembly of multidimensional framework materials using a preassembled anionic SBU {P8W48}, with integrated "pore" 1 nm in diameter, and electrophilic manganese {Mn2+} linkers. This yields two new POMOFS with augmented hexagonal tiling (2 and 3), related to a known three-dimensional (3D) cubic array K18Li6[MnII8(H2O)48PsW48O184]∙108H2O (1), K12[MnII14(H2O)30P8W48O184]∙111H2O (2), and K8Li4[MnII14(H2O)26P8W48O184]∙105H2O (3). These frameworks have been crystallized from aqueous Li-buffered solutions of {P8W48} and MnII(ClO4)2∙6H2O via careful control of the synthetic strategy akin to a crystal engineering approach using cation and temperature control to isolate different material architectures shown by compounds 1-3. [ABSTRACT FROM AUTHOR]

The convergent assembly of metal–organic frameworks has enabled the design of porous materials using a structural building unit approach, but functional systems incorporating pre-assembled structural building unit ‘pore’ openings are rare. Here, we show that the face-directed assembly of a ring-shaped macrocyclic polyoxometalate structural building unit, {P8W48O184}40− with an integrated 1-nm pore as an ‘aperture synthon’, with manganese linkers yields a vast three-dimensional extended framework architecture based on a truncated cuboctahedron. The 1-nm-diameter entrance pores of the {P8W48O184}40− structural building unit lead to approximately spherical 7.24-nm3 cavities containing exchangeable alkali-metal cations that can be replaced by transition-metal ions through a cation exchange process. Control over this process can be exerted by either electrochemically switching the overall framework charge by manipulating the oxidation state of the manganese linker ions, or by physically gating the pores with large organic cations, thus demonstrating how metal–organic framework-like structures with integrated pores and new physical properties can be assembled. [ABSTRACT FROM AUTHOR]

Based on studies with microcrystals of [Ru(bpy)3]2[α-W18O54(SO3)2] adhered to an electrode surface in contact with the ionic liquids [BMIM][PF6] and [BMIM][BF4], it has been found that a series of well defined monoelectronic reduction processes associated with the tungsten-oxo cage of the [α-W18O54(SO3)2]4−species are observed at much less negative potentials than found in conventional organic solvents. Furthermore, since the potentials of the [Ru(bpy)3]2+2,2′-bipyridyl ligand based reduction processes are not strongly medium dependent, ionic liquid investigations allowed the characterisation of the [Ru(bpy)3]2[α-W18O54(SO3)2] complex without extensive overlap of the ligand based reductions from the [Ru(bpy)3]2+cation and the [W18O54(SO3)2]4−anions. In the case of the Mo analogues, [α and β-Mo18O54(SO3)2]4−, the much higher reactivity of the reduced forms precluded access to well defined monoelectronic reversible steps at negative potentials in all media examined, even though reduction is far easier and hence availability of extensively reduced species should be simpler, in a thermodynamic sense. [ABSTRACT FROM AUTHOR]

Using multifunctional organocations a novel heteropolyanion, [(P4W6O34)2Co2Na2(H2O)2]18−, with unprecedented structural features, has been observed, and extension of these clusters from molecules into 1D chains occurs through a dimeric cobalt species, with this material exhibiting reversible colour/magnetic susceptibility changes upon dehydration. [ABSTRACT FROM AUTHOR]

A dodecanuclear FeIII complex, consisting of two {Fe6} units coupled across a single hydroxy-bridge and a cage-like PdII trimer were synthesised using the highly branched, pentadecadentate chelating ligand cis,cis-1,3,5-cyclohexanetriamine-N,N,N',N',N'',N''-hexaacetic acid (H6hact). [ABSTRACT FROM AUTHOR]

A dodecanuclear FeIIIcomplex, consisting of two {Fe6} units coupled across a single hydroxy-bridge and a cage-like PdIItrimer were synthesised using the highly branched, pentadecadentate chelating ligand cis,cis-1,3,5-cyclohexanetriamine-N,N,N′,N′,N″,N″-hexaacetic acid (H6hact). [ABSTRACT FROM AUTHOR]

Two cyclic cobalt-substituted heteropolyoxometalates K15Li5[Co10(H2O)34(P8W48O184)]·54H2O (1) and K8Li12[Co10(H2O)44(P8W48O184)]·60H2O (2) have been synthesised from the reaction of Co(ii) ions and the superlacunary {P8W48} polyanion in mildly acidic aqueous media. The cluster's anion cavities are filled with Co(ii) and K cations and careful manipulation of reaction conditions determines the formation of distinct Co-linked frameworks. [ABSTRACT FROM AUTHOR]

Cryospray mass spectrometry (CSI-MS) has been used to probe the mechanism of self-assembly of polyoxometalate clusters in solution. By using CSI-MS and electronic absorbance spectroscopy it was possible to monitor in real-time the self-assembly of polymeric chains based on [Ag2Mo8O26]2-n building blocks. The role of the AgI ion in the solution state rearrangement of molybdenum Lindqvist ({Mo6}) into the silver-linked β-octamolybdate ({Mo8}) structure ((n-C4Hg)4N)2n[Ag2Mo8O26]n (1) is revealed in unprecedented detail. A monoanionic series, in particular [AgMomO3m+1]- where m = 2 to 4, and series involving mixed oxidation state polyoxomolybdate species, which illustrate the in-solution formation of the (Ag{Mo8}Ag) building blocks, have been observed. CSI-MS detection of species with increasing metal nuclearity concomitant with increasing organic cation contribution supports the hypothesis that the organic cations used in the synthesis play an important structure-directing role in polyoxometalate (POM) growth in solution. A real-time decrease in [(Mo6)] and associated increase in [{Mo8)] have been observed using CSI-MS and electronic absorbance spectroscopy, and the rate of {Mo6} interconversion to {Mo8} was found to decrease on increasing the size of the countercation. This result can be attributed to the steric bulk of larger organic groups hindering {Mo6} to (Mo8) rearrangement and hindering the contact between silver cations and molybdenum anions. [ABSTRACT FROM AUTHOR]