Neutral dimeric metallocyclic complexes of type [M 2 (L 1 ) 2 B n ] (where M = cobalt(II), nickel(II) and zinc(II), L 1 is the doubly deprotonated form of a 1,3-aryl linked bis-b-diketone ligand of type 1,3-bis(RC(O)CH 2 C(O))C 6 H 4 (R = Me, n-Pr, t-Bu) and B is pyridine (Py) or 4-ethylpyridine (EtPy)) have been synthesised, adding to similar complexes already reported for copper(II). New lipophilic ligand derivatives with R = octyl or nonyl were also prepared for use in solvent extraction experiments. Structural, electrochemical and solvent extraction investigations of selected metal complex systems from the above series are reported, with the X-ray ] has been examined. Oxidative processes for the complexes are dominantly irreversible, but several examples of quasireversible behaviour were observed and support the assignment of an anodic process, seen between +1.0 and +1.6 V, as a metal-centred oxidation. The reduction processes for the respective metal complexes are not simple, and irreversible in most cases. Solvent extraction studies (water/chloroform) involving variable concentrations of metal, bis-b-diketone and heterocyclic base have been performed for cobalt(II) and zinc(II) using a radiotracer technique to probe the stoichiometries of the extracted species in each case. Synergism was observed when 4-ethylpyridine was added to the bis-b-diketone ligand in the chloroform phase. Competitive extraction studies show a clear uptake preference for copper(II) over cobalt(II), nickel(II), zinc(II) and cadmium(II).

Significant recent attention has been devoted to the development of useful self-assembled hybrid materials.[1] This is particularly the case for metal-organic frameworks (MOFs), which display properties such as regularity, porosity, robustness, and high surface area that lead to potential applications in areas such as catalysis, gas separation, and storage. [2,3] Our research groups and others have been developing new methods for the synthesis of both discrete and extended metal-organic materials, with particular interest in the controlled generation of increased structural complexity.[4]Herein we report a hierarchical self-assembly strategy which has been used to synthesize a new metal-organic framework. This strategy differs from the commonly employed molecular building block (MBB) and secondary building unit (SBU) approaches, where single metal ions or small inorganic clusters (polyhedra) are linked by bridging (often carboxylate) ligands in a one-pot reaction.[5] In these approaches, substantial pore volume is achieved principally through the enthalpically favorable formation of an open framework overcoming the entropic penalties associated with the entrapment of solvent guest molecules. Kinetic control over the formation of the framework is achieved largely through the trial-and-error optimization of synthetic conditions to prevent formation of unwanted kinetic intermediates. [6] In the hierarchical approach used here we have employed a series of distinct self-assembly steps, which operate across different levels of complexity, to incorporate predesigned, kinetically stable, discrete neutral supramolecular components into a metal-organic framework. In this way we show that it is possible to transcribe the properties of the discrete subcomponent into those of the framework product. This method involves the initial design and assembly of a discrete two-dimensional (2D) void-containing tecton containing unsaturated metal centers, followed by linkage of these sites with a bridging group in such a way that it is possible to transform the 2D voids in the subcomponent into 3D voids in a framework material. By using this approach we have generated a new neutral chiral MOF that displays significant porosity and gas-sorption behavior, and hence demonstrate that the host-guest properties of our discrete building blocks can be successfully imparted to the final MOF.Building on our well-established methods for assembling metallosystems incorporating b-diketone ligands, [7, 8] we constructed the large discrete triangular subcomponent [Cu 3 L 3 ]. This moiety is relatively unusual among discrete systems of this type in that it contains coordinatively unsaturated metal centers in combination with a large void area-both useful attributes for the formation of a MOF with significant porosity.H 2 L (Scheme 1) was synthesized by a Claisen condensation between dimethyl biphenyl-4,4'-dicarboxylate and 3,3-dimethylbutan-2-one (the synthesis and characterization of H 2 L is given in the Supporting Information). The target complex ...

New examples of adducts between di-(and, in one instance, tetra-) functional nitrogen ligands and planar 'platform-like' dinuclear copper(II) complexes, [Cu 2 L 2 ], incorporating the 1,3-aryl linked bis-b-diketonato bridging ligand 1,1 -(1,3-phenylene)-bis(4,4-dimethylpentane-1,3-dione) (H 2 L) have been synthesised. The X-ray structures of six adduct species are reported. The interaction of [Cu 2 (L) 2 ] with the ditopic ligand aminopyrazine (apyz) yielded the sandwich-like tetranuclear species [(Cu 2 L 2 (apyz)) 2 ]. A variable-temperature magnetochemical investigation of this product indicated weak antiferromagnetic coupling between the (five-coordinate) copper centres, mediated by the 2-aminopyrazine linkers. An analogous structure, [(Cu 2 L 2 (dabco)) 2 ] (dabco = 1,4-diazabicyclo[2.2.2]octane), was generated when dabco was substituted for aminopyrazine while use of 4,4 -dipyridyl sulfide (dps) and 4,4 -(1,3-xylylene)-bis(3,5-dimethylpyrazole) (xbp) as the ditopic 'spacer' ligands resulted in polymeric species of type [Cu 2 L 2 (dps)] n and [Cu 2 L 2 (xbp)] n , respectively. These latter species exist as one-dimensional chain structures in which copper(II) centres on different dinuclear platforms are linked in a 'zigzag' fashion. In contrast, with 2,2 -dipyridylamine (dpa) a discrete complex of type [Cu 2 L 2 (dpa) 2 ] formed in which one potential pyridyl donor from each 2,2 -dipyridylamine ligand remains uncoordinated. The use of the potentially quadruply-bridging hexamethylenetetramine (hmt) ligand as the linker unit was found to give rise to an unusual two-dimensional polymeric motif of type [(Cu 2 (L 2 ) 2 ) 3 (hmt) 2 ] n . The product takes the form of a (6,3) network, incorporating triply bridging hexamethylenetetramine units.

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New examples of nitrogen base adducts of dinuclear Co(II), Ni(II) and Cu(II) complexes of the doubly deprotonated forms of 1,3-aryl linked bis-beta-diketones of type [RC(=O)CH(2)C(=O)C(6)H(4)C(=O)CH(2)C(=O)R] (L(1)H(2)) incorporating the mono- and difunctional amine bases pyridine (Py), 4-ethylpyridine (EtPy), piperidine (pipi), 1,4-piperazine (pip), N-methylmorpholine (mmorph), 1,4-dimethylpiperazine (dmpip) and N,N,N',N'-tetramethylethylenediamine (tmen) have been synthesised by reaction of the previously reported [Cu(2)(L(1))(2)].2.5THF (R = Me), [Cu(2)(L(1))(2)(THF)(2)] (R = t-Bu), [Ni(2)(L(1))(2)(Py)(4)] (R = t-Bu) and [Co(2)(L(1))(2)(Py)(4)] (R = t-Bu) complexes with individual bases of the above type. Comparative X-ray structural studies involving all ten base adduct derivatives have been obtained and reveal a range of interesting discrete and polymeric molecular architectures. The respective products have the following stoichiometries: [Cu(2)(L(1))(2)(Py)(2)].Py (R = Me), [Cu(2)(L(1))(2)(EtPy)(2)].2EtPy (R = t-Bu), [Cu(2)(L(1))(2)(pipi)(2)].2pipi (R = t-Bu), [Cu(2)(L(1))(2)(mmorph)(2)] (R = t-Bu), [Cu(2)(L(1))(2)(tmen)(2)] (R = t-Bu) and {[Cu(2)(L(1))(2)(pip)].pip.2THF}(n), [Co(2)(L(1))(2)(tmen)(2)] (R = t-Bu), [Ni(2)(L(1))(2)(Py)(4)].dmpip (R = t-Bu), [Ni(2)(L(1))(2)(pipi)(4)].pipi (R = t-Bu) and [Ni(2)(L(1))(2)(tmen)(2)] (R = t-Bu). The effect of pressure on the X-ray structure of [Cu(2)(L(1))(2)(mmorph)(2)] has been investigated. An increase in pressure from ambient to 9.1 kbar resulted in modest changes to the unit cell parameters as well as a corresponding decrease of 6.7 percent in the unit cell volume. While a small 'shearing' motion occurs between adjacent molecular units throughout the lattice, no existing bonds are broken or new bonds formed.