Design and assembly of covalently functionalised polyoxofluorovanadate molecular hybrids

Mixed-valent polyoxometalate (POM) clusters are one of the most interesting host species showing a wide range of structural features and properties. We report the facile preparation and functionalization of a mixed-valent polyoxofluorovanadates where two electrons are trapped to antipodal sites of the clusters. The first members of this family of clusters with the general formula, [VV12VIV2O16(μ-O)10(μ3-O)10(μ3-F)2(L)2]6-, where L: py = pyridine (1); pyr = pyrazine (2); im = imidazole (3), are unique organic-inorganic hybrids with the addition of a N-donor ligand at either end of the polyoxofluorovanadate. The composition and connectivity of 1 - 3 were characterized by single-crystal X-ray diffractometry and electrospray ionization mass spectrometry. Electron paramagnetic resonance spectroscopy revealed the two well-separated VIV ions in each cluster are fully uncoupled with J = 0 giving a degenerate singlet-triplet ground state. This attenuation of the exchange interaction is probed with density functional theoretical calculations that detail the inclusion of the fluoride ion in the cluster produces a bond pathway biased toward destructive interference between competing ferromagnetic and antiferromagnetic interactions. These robust molecular materials are the ideal combination of desirable electronic properties with an organic handle with which they can be integrated into spintronic circuitry for molecular devices

Synthesis and characterisation of electronically active species

An exploration of some early transition metal (oxy) fluoride systems using solvothermal techniques has been carried out. 30 novel materials have been synthesised, which fall into three classes based on different metal centres; vanadium (21), molybdenum (5) and niobium (4). Some of these also contain secondary metal centres, namely copper (22) and zinc (1). Simultaneously, the relationship between the SHG values and the crystal structures of the hilgardites family members Pb₂B₅O₉Cl, Pb₂B₅O₉Br, Sr₂B₅O₉Cl and Ba₂B₅O₉Cl was investigated. In particular, the Pb–containing members of the hilgardite family of borate halides exhibit an abnormally large non–linear optical response, which was analysed based on neutron powder diffraction. Using solvothermal synthesis in HF–containing media, 21 novel vanadium oxyfluorides containing interesting structural features, were synthesised at 160˚C using a range of organo-amine compounds as a ligand, template, linker or structure directing agent. The architectures of the crystal structures may be categorised into; four clusters including monomeric vanadium units, five clusters including vanadium dimers, eight 1–D chains, two 2–D layers and two 3–D networks. ‘Composition–space’ diagrams with three components were used to study the effect of stoichiometry changes of reactants and to map out the crystallisation fields. The combination of early (Nb⁵⁺, Mo⁶⁺) and late (Cu²⁺) transition metals with different organo-amines produced nine novel compounds incorporating monomers, chains and 2– D interpenetrated networks. The chains and layers were synthesised from a systematic series of reactions at 160˚C and can be subdivided into four pairs, the topologies of which are essentially unique to each ligand, containing in each case a Cu–based cationic species, but alternately either [MoO₂F₄]²⁻ or [NbOF₅]²⁻, in an isomorphous manner, as the anionic moiety. The overall structures of these materials reflect the influence of the organo–amine ligands. The materials have been studied for their magnetic properties and characterised by thermogravimetric analysis, Rietveld refinement and elemental analysis where relevant

A new hybrid framework based on a 'superoctahedral' [V7O6F30](14-) polyanion

Solvothermal synthesis has led to the isolation of an unusual hybrid framework solid [CH3NH3](8)[Cu(Py)(4)](3)[V7O6F30] in which the novel [V7O6F30](14-) polyanion is linked via [Cu(py)(4)](2+) moieties into a doubly interpenetrated cubic lattice.</p

Organic-inorganic hybrid chains and layers constructed from copper-amine cations and early transition metal (Nb, Mo) oxyfluoride anions

Under hydrothermal conditions in HF-containing media, the combination of early (Nb5+, Mo6+) and late (Cu2+) transition metals with four different organic amine ligands yields eight novel hybrid compounds with chain and layer structures. The eight new compounds were synthesised from a systematic series of reactions and can be subdivided into four pairs, the topologies of which are essentially unique to each ligand, containing in each case a Cu-based cationic species, but alternately either [MoOF4](2-) or [NbOF5](2-), in an isomorphous manner, as the anionic moiety. The overall structures of theses materials reflect the influences of the organo amine ligands. [Cu(C2H4N4)(2)][MoO2F4]center dot H2O (1) and [Cu(C2H4N4)(2)][NbOF5]center dot H2O (2) exhibit an infinite copper fluoride amine chain, while the anionic moieties act as 'decoration' to the chain. [Cu(C3H4N2)(4)][MoO2F4] (3) and [Cu(C3H4N2)(4)][NbOF5] (4) form infinite 1D chains with alternating cationic and anionic units. [Cu2F2(C10H9N3)(2)][MoO2F4] (5) and [Cu2F2(C10H9N3)(2)] [NbOF4] (6) contain a dimeric copper fluoride complex, bridged through anions to form a 1D infinite chain. [Cu(C10H8N2)(2)(H2O)(2)][MoO2F4] (7) and [Cu(C10H8N2)(2)(H2O)(2)][NbOF5] (8) contain a 2D interpenetrated network formed from the copper-4,4'-bipy complex, with open channels which accommodate the oxyfluoride anions via hydrogen bond interactions.</p

A new hybrid framework based on a 'superoctahedral' [V7O6F30](14-) polyanion

Solvothermal synthesis has led to the isolation of an unusual hybrid framework solid [CH3NH3](8)[Cu(Py)(4)](3)[V7O6F30] in which the novel [V7O6F30](14-) polyanion is linked via [Cu(py)(4)](2+) moieties into a doubly interpenetrated cubic lattice.</p

Hydrothermal synthesis of vanadium oxyfluoride chains incorporating covalently bound copper coordination complexes

An exploration of the hydrothermal synthesis of vanadium oxyfluorides in the presence of copper-amine coordination complexes has produced six new compounds exhibiting novel one-dimensional structural features. [C2H8N][Cu(C5H5N)(4)][V2O2F7] incorporates dimeric vanadium(IV) oxyfluoride units (in this case, face-sharing V-centered octahedra) into a compound of this type for the first time; this composition has been prepared in two polymorphs, 1 and 2, which differ in chain configuration and orientation, mediated by H bonding of the uncoordinated dimethylammonium cation. A differing dimeric vanadium(IV) oxyfluoride anion (based on edge-sharing V-centered octahedra) occurs in [C3H5N2](2)[Cu(C3H4N2)(4)][V2O2F8], 4, which incorporates imidazole in two structural roles: as both a ligand and template. [Cu2F2(C10H10N3)(2)][V2O7], 5, and [Cu(C5H5N)(2)(C2H8N2)][(VO3)(2)], 6, both contain V5+ in tetrahedral coordination, in dimers in the former and infinite chains in the latter. In the case of 6, the copper moieties act as &quot;decoration&quot; rather than as linkers to the vanadium oxide sublattice.</p