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Issue 27, 2018
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Interesting fluorine anion water clusters [F·(H2O)n] in metal complex crystals

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Three crystalline complexes containing fluorine anion water clusters, [Cd(Im)6][F·H2O]2 (1), [Ni(Im)6][F2·(H2O)5] (2) and [Co(Im)6][F·NO3·(H2O)4] (3), were reported. The interesting fluorine anion water clusters are described in this paper. Single X-ray analysis shows that fluoride ions in the water clusters have different coordination environments, four-coordinated in a tetrahedral geometry for (1), five-coordinated in a trigonal bipyramidal geometry for (2), and three-coordinated in a planar trigonal geometry for (3). F(H2O)n is assembled by strong H-bonding interactions [OH⋯F = 2.576(1)–2.813(1) Å], where a fluoride anion plays an important role in connecting an imidazole ligand of the host [M(Im)6]2+. The strength of an ionic bond between the host and guest is strongly influenced by the F(H2O)n water cluster adjacent to the ligand with NH⋯F distances of 2.607–2.755 Å. The TGA, IR and XRD studies for the above three compounds at different testing temperatures suggested that the fluorine anion water cluster, F(H2O)n, was very stable. This result distinctly differentiates these compounds from the reported ones containing neutral water cluster molecules. This phenomenon indicated the stronger anionic hydrogen-bond interaction between F and H2O, which also confirmed the intracluster proton transfer process F·H2O → HF·OH. This result suggests that the fluorine anions and water molecules are H-bonded to each other in an alternating fashion within the fluoride−water hybrid cluster, where a fluorine anion plays the important role of connecting the host metal complex and guest water cluster.

Graphical abstract: Interesting fluorine anion water clusters [F−·(H2O)n] in metal complex crystals

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The article was received on 05 Apr 2018, accepted on 24 May 2018 and first published on 25 May 2018

Article type: Paper
DOI: 10.1039/C8CE00532J
Citation: CrystEngComm, 2018,20, 3849-3857
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    Interesting fluorine anion water clusters [F·(H2O)n] in metal complex crystals

    F. F. Jian, E. Liu and J. Y. Ma, CrystEngComm, 2018, 20, 3849
    DOI: 10.1039/C8CE00532J

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