Influence of pH and organic ligands on the supramolecular network based on molybdenum phosphate/strontium chemistry

Three supramolecular materials based on different poly(oxomolybdophosphate) clusters, (H(2)imi)(6)(Himi)(4)[{Sr(H(2)O)(4)}(2){Sr ? P(6)Mo(4)(V)Mo(14)(VI)O(73)}(2)]·17H(2)O (1), (H(2)(4,4'-bpy))(2)[Cu(2)Sr(2)Mo(12)O(24)·(OH)(6)(H(2)O)(6)(H(2)PO(4))(2)(HPO(4))(2)(PO(4))(4)]·5H(2)O (2), and (H(2)bim)(H(2)bim)[SrP(2)Mo(5)O(23)(H(2)O)(3)]·2H(2)O (3) (imi = imidazole, 4,4'-bpy = 4,4'-bipyridine, and bim = 2,2'-biimidazole), have been hydrothermally synthesized and structurally characterized by the elemental analysis, TG, IR, UV-vis, XPS and the single-crystal X-ray diffraction. Compound 1 is made up of unusual basket-shape [Sr ? P(6)Mo(18)O(73)](10-) cages linked by [Sr(H(2)O)(4)](2+) fragments to yield unprecedented dimeric chains, which represent the first 1-D assemblies of basket-type POMs. Compound 2 exhibits a novel string constructed from sandwich-like [Cu(P(4)Mo(6)O(31))(2)] units and {Sr(2)Cu} trinuclear linkers. Compound 3 is the first chain of Strandberg-type polyoxoanions connected by Sr(2+) cations. All the 1-D chains are further packed into various 3-D supramolecular assemblies via strong hydrogen-bonding interactions. The electrochemical and electrocatalysis behavior of 1, 2, and 3-CPE have been investigated in detail.     

Enclosure of a Keggin-type heteropolyoxometalate into a tubular π-space via hydrogen bonds with a nonplanar Mo(V)-porphyrin complex forming a supramolecular assembly

A 2:1 supramolecular assembly composed of a non-planar Mo(V)-porphyrin, [Mo(DPP)(O)(H(2)O)](+) (1) (DPP(2+); dodecaphenylporphyrin), and a Keggin-type heteropolyoxometalate (POM), α-[(n-butyl)(4)N](2)[SW(12)O(40)] (2), was formed via hydrogen bonds. The crystal structure was determined by X-ray crystallography to clarify that the POM was enclosed into a π-space of a supramolecular porphyrin nanotube by virtue of a hydrogen-bond network. In contrast to the formation of the 2:1 assembly ([{Mo(DPP)(O)(H(2)O)}(2)(SW(12)O(40))] (3)) between 1 and [SW(12)O(40)](2-) in the crystal, it was revealed that those two components form a 1:1 assembly in solution, in light of the results of MALDI-TOF-MS measurements in PhCN. Variable-temperature UV-vis spectroscopic titration allowed us to determine the thermodynamic parameters for the formation of the 1:1 supramolecular assembly in solution, the heat of formation (ΔH) and the entropy change (ΔS). These results provide the first thermodynamic data set to elucidate the formation process of supramolecuar structures emerged by hydrogen bonding between metalloporphyrin complexes and POMs, indicating that the formation of the assembly is an entropy-controlled process rather than an enthalpy-controlled one. Comparisons of the thermodynamic parameters with those of a planar Mo(V)-porphyrin complex also highlighted high Lewis acidity of the Mo(V) centre in the distorted porphyrin.     

Spontaneously organizing metal connectors as supramolecular structure directors of two- and three-dimensional organometallic assemblies

The supramolecular interplay of Me(3)Sn(+) and [M(CN)(2n)](n-) ions (n=3 and 4) with either 4,4'-bipyridine (bpy), trans-bis(4-pyridyl)ethene (bpe) or 4cyanopyridine (cpy) in the presence of H(2)O has been investigated for the first time. Crystal structures of the six novel assemblies: [(Me(3)Sn)(4)Mo(IV)(CN)(8).2 H(2)O.bpy] (8) and [(Me(3)Sn)(4)Mo(IV)(CN)(8).2 H(2)O.bpe] (8 a; isostructural), [(Me(3)Sn)(3)Fe(III)(CN)(6).4 H(2)O.bpy] (9), [(Me(3)Sn)(3)Co(III)(CN)(6).3 H(2)O.3/2 bpy] (10), [(Me(3)Sn)(4)Fe(II)(CN)(6).H(2)O.3/2 bpy] (11), and [(Me(3)Sn)(4)Ru(II)(CN)(6).2 H(2)O.3/2 cpy] (12) are presented. H(2)O molecules are usually coordinated to tin atoms and involved in two significant O-H.N hydrogen bonds, wherein the nitrogen atoms belong either to bpy (bpe, cpy) molecules or to M-coordinated cyanide ligands. Extended supramolecular assemblies such as -CN-->Sn(Me(3))<--O(H.)H.N(L)N.HO(H.)-->Sn(Me(3))<--NC- (L=bpy, bpe or cpy) function as efficient metal connectors (or spacers) in the structures of all six compounds. Only in the three-dimensional framework of 11, one third of all bpy molecules is involved in coordinative N-->Sn bonds. The supramolecular architecture of 9 involves virtually non-anchored (to cyanide N atoms), Me(3)Sn(+) units with a strictly planar SnC(3) skeleton, and two zeolitic H(2)O molecules. Pyrazine (pyz) is surprisingly reluctant to afford assemblies similar to 8-12, however, the genuine host-guest systems [(Me(3)Sn)(4)Mo(CN)(8).0.5pyz] and [(Me(3)Sn)(4)Mo(CN)(8).pym] (pym=pyrimidine) could be isolated and also structurally characterized.     

Nanoscale assemblies of gigantic molecular {Mo154}-rings: (dimethyldioctadecylammonium)20[Mo154O462H8(H2O)70

Clusters based on the mixed-valence gigantic inorganic ring [Mo154O462H14(H2O)70]14- ({Mo154}-ring) and dimethyldioctadecylammonium (DODA) were combined to form novel molecular assemblies of an inorganic-organic hybrid molecular system as Langmuir-Blodgett (LB) and cast films. (DODA)20[Mo154O462H8(H2O)70] (2) was prepared by cation exchange and was characterized by a combination of thermogravimetry, IR, UV-vis-NIR, 1H NMR, and XRD measurements. The salt 2 was soluble in common organic solvents, and the chemical stability of {Mo154}-ring encapsulated by DODA cationic surfactants in CHCl3 was found to be higher than that of the "native" sodium salt of the {Mo154}-ring in H2O. Uniform spherical vesicle-like molecular assemblies of (DODA)20[Mo154O462H8(H2O)70] were observed in dilute THF, whose average diameter of 95 nm and a normalized variance of 5.7% were confirmed by a X-ray small-angle scattering. Deposition of 2 as a cast film showed circular domains with a typical diameter of approximately 100 nm, indicating possible similarities between solution and surface-deposited structures. The resulting LB films of salt 2 were transferred from an acidic buffer subphase with pH = 1.5 onto mica, giving a two-dimensional film surface with a unity transfer ratio. Further, the electronic absorption spectra of the LB multilayer were consistent with the classic type II mixed-valence MoV/MoVI electronic state well know for molybdenum blue {Mo154}-ring systems, and it appears that on the surface the plane of the {Mo154}-ring is approximately parallel to the substrate surface, as indicated by polarized electronic spectra, while the alkyl chains of DODA were relatively normal to the substrate surface. Therefore, the layer between the {Mo154}-rings and DODA cations was alternately stacked along the direction of film propagation. Finally, it was found that the surface morphology of the cast and LB films was determined by the molecular assembly of (DODA)20[Mo154O462H8(H2O)70] in solution and the air-water interface, respectively.     

Synthesis and characterization of ultrathin multilayer films based on molybdenum polyoxometalate (Mo(54))

The crown-shaped molybdenum polyoxometalate cluster Na(26)[[Na(H(2)O)(2)](6)[(micro(3) -OH)(4) (Mo(20)(V)), (Mo(34)(VI)(O)(164) (micro-CH(3)COO(4)) x 120H(2)O(Mo(54)) was synthesized and first used as a bulk modifier to fabricate a three-dimensional modified WIGE electrode by the layer-by-layer method. The (Mo(54))/PAH)(n) multilayer films have been characterized by X-ray photoelectron spectra (XPS) and atomic force microscopy (AFM). UV-vis measurements reveal regular film growth with each Mo(54) adsorption. The electrochemical method was used to characterize the modified WIGE electrode, which is important for practical applications.     

Resolving self-assembly of bile acids at the molecular length scale

The self-assembly behavior of the naturally occurring steroidal bile compounds cholic, deoxycholic, ursodeoxycholic, and lithocholic acid was studied by combining atomic force microscopy (AFM), polarized optical microscopy (POM), Fourier-transform infrared spectroscopy (FTIR), absorption spectroscopy (UV-vis), circular dichroism (CD), and wide-angle X-ray scattering (WAXS). Molecular solutions of these mono-, di-, and trihydroxyl substituted bile acids spontaneously evolved into supramolecular aggregates upon the incremental addition of H(2)O as a poor solvent. Highly crystalline nanostructured multilayered assemblies were formed, which revealed a very rich polymorphism of micro- and macro-structures depending on the chemical structure of the bile acid and the properties of the cosolvent (EtOH or DMSO) used. In particular, AFM allowed resolving the crystalline structure to an unprecedented level. It was thus possible to establish that bile acids associate into H-bonded chiral dimer building blocks, which organize in 2D layers of nanostructured lamellar surface topologies with unique facial amphiphilicity. The detailed understanding of the hierarchical organization in bile acid assemblies may contribute to develop strategies to design bioinspired materials with tailor-made nanostructured surface topologies.     

Selective inclusion of Cu+ and Ag+ electron-rich metallic cations within supramolecular polyoxometalates based on {AsW9O33}{Mo3S4} combinations

Coordination of the [Mo(3)S(4)(H(2)O)(9)](4+) cluster with the trivacant [AsW(9)O(33)](9-) ion gives the supramolecular complex [{(H(4)AsW(9)O(33))(4)(Mo(3)S(4){H(2)O}(5))}(2)](12-) (1) in good yield. The structure of 1 shows that two [H(4)AsW(9)O(33)](5-) subunits sandwich a single central [Mo(3)S(4)(H(2)O)(5)](4+) ion to give a basic monomeric unit [(H(4)AsW(9)O(33))(2){Mo(3)S(4)(H(2)O)(5)}](6-). In the solid state, a supramolecular dimeric association is evidenced that consists of two [(H(4)AsW(9)O(33))(2){Mo(3)S(4)(H(2)O)(5)}](6-) units held together by twelve hydrogen bonds and four SS contacts. Complex 1 reacts with NaAsO(2), AgNO(3) and CuI to give compounds 2, 3 and 4, respectively. X-ray structural analysis reveals that the molecular arrangements of 2 to 4 are closely related to the parent structure of 1. {AsOH}(2+), Ag(+) and Cu(+) ions are located on three distinct pairs of sites. Two hanging {AsOH}(2+) groups in 2 are symmetrically attached to two opposite {AsW(9)O(33)} subunits. Complex 3 is the first example of an Ag/{Mo(3)S(4)} combination in which the environment of the two equivalent Ag(+) cations is remarkable for containing two sulfur atoms belonging to {Mo(3)S(4)}, two oxygen and one central arsenic atom of the {AsW(9)O(33)} subunits. Potentiometric titration shows that the addition of Ag(+) ions is quantitative and occurs in two successive steps (K(1)=4.1 x 10(6) and K(2)=2.3 x 10(5) L mol(-1)), which is consistent with the retention of the supramolecular cluster in solution. The structure of 4 reveals a single copper atom embedded in the central part of the dimer. The Cu(+) cation is bound to four sulfur atoms to complete a cuboidal moiety. UV/Vis studies in solution indicate that the stability of the dimeric assemblies of 2, 3 and 4 is significantly enhanced by the presence of Cu(+) or Ag(+) ions, which act as additional coordination linkers within the supramolecular cluster. The anions 1 to 4 were characterised by (183)W NMR spectroscopy in solution. The 10-line spectra recorded for each of them are consistent with an averaged C(2h) molecular symmetry in solution.     

Redox switching of polyoxometalate-methylene blue-based layer-by-layer films

Iron-substituted crown-type polyoxometalate (POM) [P(8)W(48)O(184)Fe(16)(OH)(28)(H(2)O)(4)](20-) has been successfully immobilized onto glassy carbon electrode surfaces by means of the layer-by-layer (LBL) technique employing the cationic redox active dye, methylene blue (MB). The constructed multilayers exhibit pH-dependent redox activity for both the anionic POM and the cationic dye moieties, which is in good agreement with their solution behavior. The films have been characterized by alternating current impedance, atomic force microscopy, and X-ray photoelectron spectroscopy, whereby the nature of the outer layer within the assemblies was found to have an effect upon the film's behavior. Preliminary investigations show that the POM dye-based films show electrocatalytic ability toward the reduction of hydrogen peroxide, however, only when there is an outer anionic POM layer.     

Tetra- to dodecanuclear oxomolybdate complexes with functionalized bisphosphonate ligands: activity in killing tumor cells

We report the synthesis and characterization of five novel Mo-containing polyoxometalate (POM) bisphosphonate complexes with nuclearities ranging from 4 to 12 and with fully reduced, fully oxidized, or mixed-valent (Mo(V), Mo(VI)) molybdenum, in which the bisphosphonates bind to the POM cluster through their two phosphonate groups and a deprotonated 1-OH group. The compounds were synthesized in water by treating [Mo(V)(2)O(4)(H(2)O)(6)](2+) or [Mo(VI)O(4)](2-) with H(2)O(3)PC(C(3)H(6)NH(2))OPO(3)H(2) (alendronic acid) or its aminophenol derivative, and were characterized by single-crystal X-ray diffraction and (31)P NMR spectroscopy. (NH(4))(6)[(Mo(V)(2)O(4))(Mo(VI)(2)O(6))(2)(O(3)PC(C(3)H(6)NH(3))OPO(3))(2)]·12H(2)O (1) is an insoluble mixed-valent species. [(C(2)H(5))(2)NH(2)](4)[Mo(V)(4)O(8)(O(3)PC(C(3)H(6)NH(3))OPO(3))(2)]·6H(2)O (2) and [(C(2)H(5))(2)NH(2)](6)[Mo(V)(4)O(8)(O(3)PC(C(10)H(14)NO)OPO(3))(2)]·18H(2)O (4) contain similar tetranuclear reduced frameworks. Li(8)[(Mo(V)(2)O(4)(H(2)O))(4)(O(3)PC(C(3)H(6)NH(3))OPO(3))(4)]·45H(2)O (3) and Na(2)Rb(6)[(Mo(VI)(3)O(8))(4)(O(3)PC(C(3)H(6)NH(3))OPO(3))(4)]·26H(2)O (5) are alkali metal salts of fully reduced octanuclear and fully oxidized dodecanuclear POMs, respectively. The activities of 2-5 (which are water-soluble) against three human tumor cell lines were investigated in vitro. Although 2-4 have weak but measurable activity, 5 has IC(50) values of about 10 μM, which is about four times the activity of the parent alendronate molecule on a per-alendronate basis, which opens up the possibility of developing novel drug leads based on Mo bisphosphonate clusters.     

Electrochemistry of ITO electrode modified by multilayer ultrathin films based on crown-shaped polyoxomolybdate

The electrochemical multilayer films of crown-shaped polyoxomolybdate Na21{[Na5(H2O)14] intersection[Mo(V)(20)Mo(VI)(26)O134(OH)10(mu-CH3COO)4]}.CH3COONa.90H2O (Mo46) and polyelectrolytes by layer-by-layer assembly were investigated. The stable multilayer films were assembled by alternate adsorption of negatively charged POM and positively charged polyelectrolytes is from their aqueous dispersions. UV-vis spectroscopy and cyclic voltammetry were used to monitor the regular growth of the multilayer films. The multilayer films-modified ITO electrode was used for the detection of electrocatalytic activity toward the reduction of nitrite, bromate, and hydrogen peroxide. The proposed novel immobilized method exhibited good stability, reproducibility and high sensitivity for the determination of electrocatalytic, which is important for practical application.     

Crystal structures and solution properties of discrete complexes composed of saddle-distorted molybdenum(v)-dodecaphenylporphyrins and keggin-type heteropolyoxometalates linked by direct coordination

Reactions of a saddle-distorted Mo(V)-porphyrin complex, [Mo(DPP)(O)(H(2)O)]ClO(4) (1·ClO(4); DPP(2-) = dodecaphenylporphyrin dianion), with tetra-n-butylammonium (TBA) salts of Keggin-type heteropolyoxomatalates (POMs), α-[XW(12)O(40)](n-) (X = P, n = 3, 2; X = Si, n = 4, 3; X = B, n = 5; 4), in ethyl acetate/acetonitrile gave 2:1 complexes formulated as [{Mo(DPP)(O)}(2)(HPW(12)O(40))] (5), [{Mo(DPP)(O)}(2)(H(2)SiW(12)O(40))] (6), and [(n-butyl)(4)N](2)[{Mo(DPP)(O)}(2)(HBW(12)O(40))] (7) under mild reaction conditions. The crystal structures of the complexes were determined by X-ray crystallography. In these three complexes, named Porphyrin Hamburgers, the POM binds to two Mo(V) centers of porphyrin units directly via coordination of two terminal oxo groups. In spite of the similarity of those POM's structures, those Porphyrin Hamburgers exhibit different coordination bond angles between POM and the Mo(V) center in the porphyrin: 5 and 7 show two different coordination bond angles in one molecule in contrast to 6, which exhibits only one coordination bond angle. The Porphyrin Hamburgers involve protonation of the POM moieties to adjust the charge balance, as confirmed by spectroscopic titration with bases. In the crystals, the Porphyrin Hamburgers form two-dimensional (2D) sheets in the ac plane based on π-π interactions among peripheral phenyl substituents. Stacking of the 2D sheets toward the b axis constructs a 3D layered structure involving channels running into the crystallographic [1 0 0] and [0 0 1] directions in the crystal to include solvent molecules of crystallization for 5-7, and also counter cations for 7. Three complexes were revealed to be stable enough to maintain their structures even in solutions to show molecular ion peaks in the MALDI-TOF-MS measurements. They also exhibited different electron paramagnetic resonance (EPR) signals because of the Mo(V) (S = 1/2, I = 0) centers, reflecting the difference in the crystal structures. In addition, these complexes showed reversible multistep redox processes as observed in their cyclic voltammograms in benzonitrile to demonstrate high stability throughout the redox reactions in solution.     

A series of new organic-inorganic molybdenum arsenate complexes based on [(ZnO6)(As3O3)2Mo6O18]4- and [HxAs2Mo6O26](6-x)- clusters as SBUs

By synthesizing the novel molybdenum arsenate complexes, we have obtained eight new structures, namely, (4,4'-bipy)[Zn(4,4'-bipy)2(H2O)2]2[(ZnO6)(AsIII3O3)2Mo6O18].7H2O, 1, [Zn(phen)2(H2O)]2[(ZnO6)(AsIII3O3)2Mo6O18].4H2O, 2, [Zn(2,2'-bipy)2(H2O)]2[(ZnO6)(AsIII3O3)2Mo6O18].4H2O, 3, [Zn(H4,4'-bipy)2(H2O)4][(ZnO6)(AsIII3O3)2Mo6O18].8H2O, 4, (H24,4'-bipy)[CuI(4,4'-bipy)]2[H2AsV2Mo6O26].H2O, 5, (H24,4'-bipy)3[AsV2Mo6O26].4H2O, 6, (H24,4'-bipy)3[AsV2Mo6O26(H2O)].4H2O, 7, and (H24,4'-bipy)2.5(H3O)[AsV2Mo6O26(H2O)].1.25H2O, 8 (4,4'-bipy = 4,4'-bipyridine, 2,2'-bipy = 2,2'-bipyridine, phen = 1,10-phenanthroline). These structures were determined by single-crystal X-ray diffraction analysis and were further characterized by elemental analysis, IR, XPS spectroscopy, and TG analysis. The structure of 1 is constructed from two-dimensional square gridlike sheets linked by the polyanions [(ZnO6)(AsIII3O3)2Mo6O18]4- via hydrogen-bonding interactions to form a three-dimensional supramolecular framework with two types of channels. Compounds 2 and 3 display similar bisupported structures. Compound 4 features a three-dimensional supramolecular architecture. Compound 5 possesses a 1D infinite ladderlike ribbon. Compounds 6-8 are discrete structures exhibiting three isomeric forms of [HxAs2Mo6O26](6-x)-. Furthermore, compound 8 represents a new isomer B'-[As2Mo6O26(H2O)]6-. In addition, the fluorescent properties of compounds 1-3 are reported.     

Construction of Ag/1,2,4-triazole/polyoxometalates hybrid family varying from diverse supramolecular assemblies to 3-d Rod-packing framework

Eight members of the Ag/1,2,4-triazole/polyoxometalates (POMs) hybrid supramolecular family, namely, [Ag4(dmtrz)4][Mo8O26] (dmtrz=3,5-dimethyl-1,2,4-triazole, 1), [Ag6(3atrz)6][PMo12O40]2.H2O (3atrz=3-amino-1,2,4-triazole, 2), [Ag2(3atrz)2]2[HPMoVI10MoV2O40] (3), [Ag2(dmtrz)2]2[HPMoVI10MoV2O40] (4), [Ag2(trz)2]2[Mo8O26] (trz=1,2,4-triazole, 5), [Ag2(3atrz)2][Ag2(3atrz)2(Mo8O26)] (6), [Ag4(4atrz)2Cl][Ag(Mo8O26)] (4atrz=4-amino-1,2,4-triazole, 7), and [Ag5(trz)4]2[Ag2(Mo8O26)].4H2O (8), were synthesized through hydrothermal reactions of 1,2,4-triazole or its derivatives with appropriate silver salts and molybdates. Crystal structure analysis reveals that the POM-dependent Ag-1,2,4-triazolate units in these hybrid compounds form a novel tetranuclear cluster (1), a unique double calix[3]arene-shaped hexamer (2), zigzag chains (5 and 6), helix chains (3, 4, and 8), and an interesting looped chain (7). A series of hydrogen bonding-based supramolecular assemblies varying among the 0-D+0-D (1 and 2), 0-D+1-D (3 and 4), 1-D+1-D (5 and 7), and 1-D+2-D (6) modes between the organomatic cations and POM anions were observed in these structures. Moreover, the inorganic chain [Ag(Mo8O26)]n3n- in 7 constructed by the building block [Mo8O26]4- linked only via single Ag+ ion is unprecedented. Compound 8 is the first high-dimensional framework constructed from the [Ag2(Mo8O26)]n2n- rod-shaped subunits. These hybrid supramolecular compounds present interesting photochemical properties. The spectroscopic experiments show that they not only are potential semiconductor materials but also have interesting photoluminescence phenomena, including O-->Mo [LMCT] and intraligand [pi-pi*] emissions generated by internal heavy metal effect.     

Aqueous-mixed ionic liquid system: phase transitions and synthesis of gold nanocrystals

Micelle-vesicle-micelle (MVM) transitions are observed in the aqueous-mixed ionic liquid (1-butyl-3-methylimidazolium octyl sulfate and 3-methyl-1-octylimidazolium chloride) system. The surface activity of mixed ILs, phase behavior, and solution structures in the system have been thoroughly characterized using conductometry, tensiometry, fluorimetry, dynamic light scattering (DLS), viscometry, turbidity, atomic force microscopy (AFM), transmission electron microscopy (TEM), and (1)H NMR techniques. Synergetic interactions between the two ILs in monolayers at the air/water interface and in micelles/vesicles have been determined using the regular solution approach, and the origins of spontaneous vesicle formation in this novel system are discussed. Using a photoreduction method, the formation of stable gold nanoparticles (GNPs) and microscale nanosheets of different shapes and sizes in the micellar and vesicle solutions has been reported. The studies show the potential of a mixed IL system in constructing stable micelles/supramolecular assemblies, such as bilayer vesicles, which are effective in the preparation of the desired nanomaterials.     

One inorganic-organic hybrid derived from reduced molybdophosphate and trinuclear cadmium(Ⅱ) fragment

One new polyoxometalate (POM)-based inorganic-organic hybrid [Cd3Ⅱ(HPO4)(Hbpp)(H2O)2]{CdⅡ[P4- Mo6O28H3.5(OH)3]2} (H4tpb)·7H2O (1) (bpp = 1,3-bis-(4-pyridyl)propane, tpb = 1,2,4,5-tetra(4-pyridyl)-benzene) constructed from reduced molybdophosphate [P4Mo6O28H3.5(OH)3]5.5- (P4Mo6), trinuclear CdⅡ-phosphate-Hbpp fragment and protonated tpb has been hydrothermally synthesized and structurally characterized by IR, elemental analyses and single crystal X-ray diffraction. The complex 1 crystallizes in the monoclinic system with the space group P21/c and cell parameters of a = 15.672(12)Å, b = 23.839(19)Å, c = 27.654(2)Å, β = 115.850(10)8, V = 9297.9(12) Å3, Z = 4, R1 = 0.0534 and wR2 = 0.1135. In complex 1, the P4Mo6 units are bridged by CdⅡ ions to form the classic sandwich-type [Cd(P4Mo6)2] dimers, which are further connected into a two dimensional network via the trinuclear CdⅡ subunits. The tpb is synthesized in situ from the bpp ligands and connects the adjacent 2D layers into a 3D supramolecular framework through hydrogen bonding interactions. The electrochemical and fluorescent properties of complex 1 have been investigated.     

Control over Nanostructures and Associated Mesomorphic Properties of Doped Self‐Assembled Triarylamine Liquid Crystals

We have synthesized a series of triarylamine‐cored molecules equipped with an adjacent amide moiety and dendritic peripheral tails in a variety of modes. We show by ¹H NMR and UV/Vis spectroscopy that their supramolecular self‐assembly can be promoted in solution upon light stimulation and radical initiation. In addition, we have probed their molecular arrangements and mesomorphic properties in the bulk by integrated studies on their film state by using differential scanning calorimetry (DSC), variable‐temperature polarizing optical microscopy (VT‐POM), variable‐temperature X‐ray diffraction (VT‐XRD), and atomic force microscopy (AFM). Differences in the number and the disposition of the peripheral tails significantly affect their mesomorphic properties associated with their lamellar‐ or columnar‐packed nanostructures, which are based on segregated stacks of the triphenylamine cores and the lipophilic/lipophobic periphery. Such structural tuning is of interest for implementation of these soft self‐assemblies as electroactive materials from solution to mesophases.     

New high-dimensional networks based on polyoxometalate and crown ether building blocks

Three novel supramolecular assemblies constructed from polyoxometalate and crown ether building blocks, [(DB18C6)Na(H(2)O)(1.5)](2)Mo(6)O(19).CH(3)CN, 1, and [(Na(DB18C6)(H(2)O)(2))(3)(H(2)O)(2)]XMo(12)O(40).6DMF.CH(3)CN (X = P, 2, and As, 3; DB18C6 = dibenzo-18-crown-6; DMF = N,N-dimethylfomamide), have been synthesized and characterized by elemental analyses, IR, UV-vis, EPR, TG, and single crystal X-ray diffraction. Compound 1 crystallizes in the tetragonal space group P4/mbm with a = 16.9701(6) A, c = 14.2676(4) A, and Z = 2. Compound 2 crystallizes in the hexagonal space group P6(3)/m with a = 15.7435(17) A, c = 30.042(7) A, gamma = 120 degrees, and Z = 2. Compound 3 crystallizes in the hexagonal space group P6(3)/m with a = 15.6882(5) A, c = 29.9778(18) A, gamma = 120 degrees, and Z = 2. Compound 1 exhibits an unusual three-dimensional network with one-dimensional sandglasslike channels based on the extensive weak forces between the oxygen atoms on the [Mo(6)O(19)](2)(-) polyoxoanions and the CH(2) groups of crown ether molecules. Compounds 2 and 3 are isostructural, and both contain a novel semiopen cagelike trimeric cation [(Na(DB18C6)(H(2)O)(2))(3)(H(2)O)(2)](3+). In their packing arrangement, an interesting 2-D "honeycomblike" "host" network is formed, in which the [XMo(12)O(40)](3)(-) (X = As and P) polyoxoanion "guests" resided.     

Isolated and linear arrays of surfactant-encapsulated polyoxometalate clusters on graphite

We report on the self-assembly of several surfactant-encapsulated clusters (SECs) on the basal plane of graphite consisting of the doughnut-shaped tungstophosphate anion [Na(H2O)P5W30O110] covered by a hydrophobic shell of surfactants. Well-ordered rodlike structures are observed using scanning force microscopy. No such ordering is observed if the surfactant methyltrioctadecylammonium is used for encapsulation, suggesting that the density of alkyl chains around the polyoxometalate cluster is an important factor in determining the order of SEC assemblies on graphite. Coadsorption of tetratetracontane (n-C44H90) and (DODA)14[Na(H2O)P5W30O110] results in single, isolated SECs on a buffer layer of tetratetracontane, as determined by scanning tunneling microscopy.     

Polyoxometalates functionalized by bisphosphonate ligands: synthesis, structural, magnetic, and spectroscopic characterizations and activity on tumor cell lines

We report the synthesis and characterization of eight new Mo, W, or V-containing polyoxometalate (POM) bisphosphonate complexes with metal nuclearities ranging from 1 to 6. The compounds were synthesized in water by treating Mo(VI), W(VI), V(IV), or V(V) precursors with biologically active bisphosphonates H(2)O(3)PC(R)(OH)PO(3)H(2) (R = C(3)H(6)NH(2), Ale; R = CH(2)S(CH(3))(2), Sul and R = C(4)H(5)N(2), Zol, where Ale = alendronate, Sul = (2-Hydroxy-2,2-bis-phosphono-ethyl)-dimethyl-sulfonium and Zol = zoledronate). Mo(6)(Sul)(2) and Mo(6)(Zol)(2) contain two trinuclear Mo(VI) cores which can rotate around a central oxo group while Mo(Ale)(2) and W(Ale)(2) are mononuclear species. In V(5)(Ale)(2) and V(5)(Zol)(2) a central V(IV) ion is surrounded by two V(V) dimers bound to bisphosphonate ligands. V(6)(Ale)(4) can be viewed as the condensation of one V(5)(Ale)(2) with one additional V(IV) ion and two Ale ligands, while V(3)(Zol)(3) is a triangular V(IV) POM. These new POM bisphosphonates complexes were all characterized by single-crystal X-ray diffraction. The stability of the Mo and W POMs was studied by (31)P NMR spectroscopy and showed that all compounds except the mononuclear Mo(Ale)(2) and W(Ale)(2) were stable in solution. EPR measurements performed on the vanadium derivatives confirmed the oxidation state of the V ions and evidenced their stability in aqueous solution. Electrochemical studies on V(5)(Ale)(2) and V(5)(Zol)(2) showed reduction of V(V) to V(IV), and magnetic susceptibility investigations on V(3)(Zol)(3) enabled a detailed analysis of the magnetic interactions. The presence of zoledronate or vanadium correlated with the most potent activity (IC(50)~1-5 μM) against three human tumor cell lines.     

Star-like supramolecular polymers fabricated by a Keplerate cluster with cationic terminated polymers and their self-assembly into vesicles

The electrostatic combination of a Keplerate cluster, [Mo(132)O(372)(CH(3)COO)(30)(H(2)O)(72)](42-) with cationic terminated poly(styrene) yields polyoxometalate-based supramolecular star polymers, which can further self-assemble into vesicular aggregates in CHCl(3)-MeOH mixed solvent.