Anion-directed supramolecular chemistry modulating the magnetic properties of nanoscopic Mn coordination clusters: from polynuclear high-spin complexes to SMMs.

We report a supramolecular approach to mixed-valent Mn coordination clusters that demonstrates how halide ions can be applied to influence the assembly of distinct tetranuclear building units to produce a number of related Mn coordination clusters with dense core structures that derive from a cuboctahedral arrangement of Mn ions. In all compounds the alignment of the Jahn-Teller axes of the MnIII centers coincides with the positions of the stabilizing chloride ligands. Thus, the relative chloride concentrations in the reaction mixtures allow us to modify the symmetry and magnetic anisotropy of this basic core structures resulting in isotropic polynuclear high-spin complexes at high Cl- concentrations and Single-Molecule Magnets at lower relative Cl- concentrations.

Photoluminescent lead(II) coordination polymers stabilised by bifunctional organoarsonate ligands.

Four lead(II) coordination polymers were isolated under hydro(solvo)thermal conditions. The applied synthetic methodology takes advantage of the coordination behaviour of a new bifunctional organoarsonate ligand, 4-(1, 2, 4-triazol-4-yl)phenylarsonic acid (H2TPAA) and involves the variation of lead(II) reactants, metal/ligand mole ratios, and solvents. The constitutional composition of the four lead(II) coordination polymers can be formulated as [Pb2(TPAA)(HTPAA)(NO3)]·6H2O (1), [Pb2(TPAA)(HTPAA)2]·DMF·0.5H2O (DMF = N, N-Dimethylformamide) (2), [Pb2Cl2(TPAA)H2O] (3), and [Pb3Cl(TPAA)(HTPAA)2H2O]Cl (4). The compounds were characterized by single-crystal and powder x-ray diffraction techniques, thermogravimetric analyses, infra-red spectroscopy, and elemental analyses. Single-crystal x-ray diffraction reveals that 1 and 2 represent two-dimensional (2D) layered structures whilst 3 and 4 form three-dimensional (3D) frameworks. The structures of 1, 2, and 4 contain one-dimensional (1D) {PbII/AsO3} substructures, while 3 is composed of 2D {PbII/AsO3} arrays. Besides their interesting topologies, 1-4 all exhibit photoluminescence properties in the solid state at room temperature.

Homologous size-extension of hybrid vanadate capsules - solid state structures, solution stability and surface deposition.

The dimensions and cavity sizes of the molecular capsules with the general formula [V10O18L4](10-) can be controlled modularly through the nature of the bifunctional, rigid organophosphonate ligands L(1) and L(2) (L(1) = bis(4-phosphonatophenyl)ethyne and L(2) = bis(4-phosphonatophenyl)butadiyne); the solution stability of the molecular entities as demonstrated by ESI-MS studies permits their assembly on the Au(111) surface on a sub-monolayer scale giving rise to a 2D supramolecular structure that is comparable to the packing arrangements of the capsules in the crystal structures.

A facile "bottom-up" approach to prepare free-standing nano-films based on manganese coordination clusters.

We present herein a novel method to prepare free-standing Dried Foam Films (DFFs) whereby individual polynuclear manganese complexes cover quantitatively the holes of micro-grids; the fabricated, homogeneous films have a cross-sectional thickness of only ca. 5 nm and are characterised by high mechanical stability.

Supramolecular approach by using Jahn-Teller sites to construct a {Mn13}-based coordination polymer and modify its magnetic properties.

Put a spin on it: a {Mn(13)} coordination cluster has been used as a secondary building unit for the preparation of an open-framework structure for which the magnetic properties can be modified by solution adsorption of tetracyanoquinodimethane radical anions (TCNQ·(-)). The applied supramolecular approach takes advantage of kinetically labile Jahn-Teller sites and can be generalised for the construction and post-synthetic modification of multifunctional materials.

Self-assembly of hybrid organic-inorganic polyoxomolybdates: solid-state structures and investigation of formation and core rearrangements in solution.

We report here a facile synthetic and analytical approach that allows us to identify and characterize functionalized polyoxomolybdate clusters that form upon the partial reduction of Mo(VI) salts in the presence of organoarsonate ligands. We demonstrated that electrospray ionization mass spectrometry, in combination with X-ray crystallography, provides an extremely powerful tool, allowing us to exploit slight perturbations of the ligand structures for the preparation of a series of unprecedented cluster compounds. Redox-active transition metals that adopt cubane or related structures are of particular interest because of their resemblance to active sites of enzymes. Our investigations underline the stability of the hybrid compounds in solution, an essential requirement for potential applications as catalysts. Supplemental analyses include measurements of the magnetic properties, NMR, IR, UV/vis, and bond-valence-sum analyses. Our results highlight the possibility of exploring real-time growth reactions of polyoxometales that emerge in solution and transform to produce hybrid organic-inorganic polyoxometalate clusters.