We present a comprehensive study of the partially reduced polyoxomolybdate [H 3 Mo 57 V 6 (NO) 6 (2) was isolated as a dark violet solid, which readily dissolves in organic solvents. Slow evaporation of solutions of 2 on solid substrates forces the hydrophobic particles to aggregate into a cubic lattice. Annealing these so-formed films at elevated temperature causes de-wetting with terrace formation similar to liquid crystals and block copolymers. Compound 2 forms a stable Langmuir monolayer at the air ± water interface; Langmuir ± Blodgett multilayers are readily prepared by repeated transfer of monolayers on solid substrates. The films were characterized by optical ellipsometry, Brewster angle microscopy, transmission electron microscopy, and X-ray reflectance.

We describe the spontaneous self-assembly and the superstructure of a discrete surfactant-encapsulated cluster, (DODA) 40 (NH 4 ) 2 [(H 2 O) n ⊂Mo 132 O 372 (CH 3 COO) 30 (H 2 O) 72 ] (2, n ≈ 50), which consists of a hollow giant isopolyoxomolybdate core covered by a hydrophobic shell of dimethyldioctadecylammonium (DODA) cations. The structural characterization of these nanoporous core-shell particles is based on small-angle X-ray scattering (SAXS) data on solutions of the encapsulated clusters, TEM investigations, FT-IR and UV-vis spectroscopy, as well as determination of the molecular area of 2 by Langmuir film investigations. Computer modeling of the solvent-accessible surface of the encapsulated cluster yields a central cavity with a volume of 1.5 nm 3 that is occupied by approximately 50 H 2 O molecules. The cluster bears (Mo-O) 9-ring openings with an average diameter of 0.43 nm. The covered surface area of 84 Å 2 /DODA indicates a rather tight packing of the amphiphile at the cluster surface. Due to the unique supramolecular architecture of 2 as well as its high solubility in common organic solvents, this compound shows promising perspectives for future applications in host-guest chemistry and homogeneous size-selective catalysis.

A detailed analysis of the supramolecular architecture of the nanoporous surfactant-encapsulated cluster (SEC) with the empirical formula (DODA) 40 (NH 4 The open framework architecture of the Keplerate cluster is investigated by means of small angle neutron scattering (SANS) in CDCl 3 solutions containing discrete SECs. A simplifying core-shell model of 1 is developed, which describes the SEC as a solvent-filled nanocavity, surrounded by two concentric shells (a first polyoxometalate shell of 2.96 nm outer diameter, and a consecutive surfactant shell of 6.18 nm outer diameter, respectively). The model is successfully applied to probe the content of H 2 O/D 2 O guest molecules in the Keplerate host. Different surface analytical techniques are applied to characterize the hierarchical structures of monolayers and thin films of 1. Monolayers at the air-water interface are investigated by means of optical ellipsometry and Brewster angle microscopy. Electron density profiles of the monolayers of 1 are gained from synchrotron X-ray reflectance (XRR) measurements that provide further evidence for the supramolecular core-shell architecture of the SEC. Within the spatial resolution limits of these analytical methods, the current data support a monolayer model consisting of hexagonal close-packed arrays of discrete SECs, floating at the air-water interface. Langmuir-Blodgett (LB) transfer of compressed monolayers on to a solid substrate leads to homogeneous multilayers. In the XRR spectra of LB multilayers of 1 multiple Bragg reflections appear, thus indicating an intrinsic tendency of the SECs to adapt a 3-dimensional, highly ordered solid state structure. Considering the huge variety of structurally different polyoxometalates and the possibility to tailor the surfactant shell by means of classic organic synthesis, the selforganization of hierarchically structured thin films and solids based on SECs bears promising perspectives towards the engineering of functional materials. † Based on the presentation given at Dalton Discussion No. 3,

Anisotropic thin film materials of metallosupramolecular polyelectrolyte-amphiphile complexes (denoted PACs) with structures at several length scales were fabricated through a multistep self-assembly process. Metal ion-mediated self-assembly of the ditopic ligand 1,4-bis(2,2:6,2-terpyridine-4-yl)benzene and electrostatic binding with the amphiphile dihexadecyl phosphate result in a PAC with tailored surface chemical properties, including solubility and surface activity. The PAC forms a stable monolayer at the air-water interface that is readily transferred and oriented on solid supports with the Langmuir-Blodgett technique. The presented strategy unifies colloid and metallosupramolecular chemistry and opens a versatile route to hierarchical materials with tailored structures and functions.T he design and construction of supramolecular architectures of nanoscopic dimensions give access to entities of increasing complexity with distinct structural and functional properties (1). The use of intermolecular forces provides a rational and efficient method to position molecular components precisely in a well defined supramolecular architecture (2). Self-assembly relies on a sequence of spontaneous recognition, growth, and termination steps to form the final equilibrium supramolecular entity (or a collection of such) through metal ion coordination, hydrogen bonds, or hydrophobic or electrostatic interactions. Applications of such systems in materials science, medicine, and chemical technology are diverse, including recognition (sensing), transformation (catalysis), and translocation (signal transduction) devices.Although the principles that govern self-assembly of discrete supramolecular assemblies are well understood, the fabrication of (extended) structures with more than one length scale is the next challenge in the implementation of supramolecular devices in functional materials (3). Correlation of positions and orientations of the constituents in a material, preferentially over a long range, is of paramount importance to exploit the properties of supramolecular devices fully, for example in vectorial transport processes, such as light-to-energy conversion, or to establish an electronic band structure as in semiconductors (4 -6). To achieve this goal, it will be necessary to improve existing and to innovate new methods to fabricate hierarchical materials. The Langmuir-Blodgett (LB) technique was one of the first methods to fabricate films with a well defined architecture and played a key role in the development of molecular electronics (7). Other approaches include the engineering of crystals (8), liquid crystalline materials, and lyotropic mesophases (9). However, the implementation of metallosupramolecular devices in ordered hierarchical architectures has not been realized to date.Metal-ion-directed self-assembly is of particular interest for the construction of functional devices (10). Metal ions possess a range of well defined coordination geometries and diverse properties that are relevant in electronic and phot...

Combining analytical and theoretical methods, we present a detailed study of a heteropolytungstate cluster encapsulated in a shell of dendritically branching surfactants, namely (C(52)H(60)NO(12))(12)[(Mn(H(2)O))(3)(SbW(9)O(33))(2)], 3. This novel surfactant-encapsulated cluster (SEC) self-assembles spontaneously from polyoxometalate-containing solutions treated with a stoichiometric amount of dendrons. Compound 3 exhibits a discrete supramolecular architecture in which a single polyoxometalate anion resides in a compact shell of dendrons. Our approach attempts to combine the catalytic activity of polyoxometalates with the steric properties of tailored dendritic surfactants into size-selective catalytic systems. The structural characterization of the SEC is based on analytical ultracentrifugation (AUC) and small-angle neutron scattering (SANS). The packing arrangement of dendrons at the cluster surface is gleaned from molecular dynamics (MD) simulations, which suggests a highly porous shell structure due to the dynamic formation of internal clefts and cavities. From analysis of the MD trajectory of 3, a theoretical neutron-scattering function is derived that is in good agreement with experimental SANS data. Force field parameters used in MD simulations are partially derived from a quantum mechanical geometry optimization of [(Zn(H(2)O))(3)(SbW(9)O(33))(2)](12)(-), 2b, at the density functional theory (DFT) level. DFT calculations are corroborated by X-ray structure analysis of Na(6)K(6)[(Zn(H(2)O))(3)(SbW(9)O(33))(2)].23H(2)O, which is isostructural with the catalytically active Mn derivative 2a. The combined use of theoretical and analytical methods aims at rapidly prototyping smart catalysts ("dendrizymes"), which are structurally related to naturally occurring metalloproteins.

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A detailed analysis of a metallosupramolecular coordination polyelectrolyte-amphiphile complex (PAC) at the air/water interface is presented based on Langmuir isotherm measurements, Brewster angle microscopy as well as X-ray reflectance and diffraction measurements. The PAC is prepared in solution by metal-ion coordination of Fe(OAc)2 and 1,4-bis(2,2':6',2"-terpyridin-4'-yl)benzene followed by self-assembly with dihexadecyl phosphate (DHP). The spreading of the PAC at the air/water interface results in a Langmuir film with a stratified architecture, such that DHP forms a monolayer on the water surface, while the metallosupramolecular coordination polyelectrolyte (MEPE) is immersed in the aqueous subphase. Electrostatic interactions of MEPE and DHP force the alkyl chains into an upright, hexagonal lattice even at low surface pressures. This work illustrates how supramolecular, colloidal, and surface chemistry can be combined to create complex architectures with tailored characteristics that may not be accessible through self-organization in the liquid phase.

A detailed analysis of a metallosupramolecular polyelectrolyte-amphiphile complex (PAC) at the air-water interface is presented. Langmuir isotherms, Brewster angle microscopy, and X-ray reflectance and diffraction methods are employed to investigate the structure of the Langmuir monolayers. The PAC is self-assembled from 1,3-bis[4'-oxa-(2,2':6',2' '-terpyridinyl)]propane, iron acetate, and dihexadecyl phosphate (DHP). Spreading the PAC at the air-water interface results in a monolayer that consists of two strata. DHP forms a monolayer at the top of the interface, while the metallosupramolecular polyelectrolyte is immersed in the aqueous subphase. Both strata are coupled to each other through electrostatic interactions. The monolayers can be transferred onto solid substrates, resulting in well-ordered multilayers. Such multilayers are model systems for well-ordered metal ions in two dimensions.