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Issue 40, 2011
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Molecular squares, cubes and chains from self-assembly of bis-bidentate bridging ligands with transition metal dications

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Abstract

The two new ligands Lfur and Lth consist of two chelating pyrazolyl-pyridine termini connected to furan-2,5-diyl or thiophene-2,5-diyl spacers viamethylene groups. Reaction of these with a range of transition metal dications that prefer octahedral coordination affords a series of unusual structures which are all based on a 2M : 3L ratio. [M8(Lfur)12]X16 (M = Co, Cu, X = BF4; and M = Zn, X = ClO4) are octanuclear cubes with approximate D4 symmetry in which two cyclic tetranuclear helicate M4L4 units are connected by four additional ‘pillar’ ligands. In contrast [Ni4(Lfur)6](BF4)8 is a centrosymmetric molecular square consisting of two dinuclear Ni2L2 units of opposite chirality that are connected by a pair of additional Lfur ligands such that the four edges of the Ni4 square are spanned by alternately two and one bridging ligands. [M4(Lth)6](BF4)8 (M = Co, Ni, Cu) are likewise molecular squares with similar structures to [Ni4(Lfur)6](BF4)8 with the significant difference that the two crosslinked double helicate M2L2 units are now homochiral. The Cd(II) complexes both behave quite differently to the first-row metal complexes, with [Cd(Lfur)(BF4)](BF4) being a simple mononuclear complex with a single ligand in which the furan oxygen atom is weakly interacting with the Cd(II) centre. In contrast, in {[Cd2(Lth)3](BF4)4}, where this quasi-pentadentate coordination mode of the ligand is not possible because thiophene is too poor an electron donor, the ligand reverts to bis-bidentate bridging coordination to afford a one-dimensional chain consisting of an infinite sequence of crosslinked, homochiral, Cd2(Lth)2 double helicate units.

Graphical abstract: Molecular squares, cubes and chains from self-assembly of bis-bidentate bridging ligands with transition metal dications

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Publication details

The article was received on 17 Feb 2011, accepted on 29 Mar 2011 and first published on 26 Apr 2011


Article type: Paper
DOI: 10.1039/C1DT10263J
Dalton Trans., 2011,40, 10360-10369

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    Molecular squares, cubes and chains from self-assembly of bis-bidentate bridging ligands with transition metal dications

    A. Stephenson and M. D. Ward, Dalton Trans., 2011, 40, 10360
    DOI: 10.1039/C1DT10263J

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