title: Desymmetrization of an Octahedral Coordination Complex Inside a Self-Assembled Exoskeleton.
abstract: The synthesis of a centrally functionalized, ribbon-shaped [6]polynorbornane ligand L that self-assembles with Pd(II) cations into a {Pd2 L4 } coordination cage is reported. The shape-persistent {Pd2 L4 } cage contains two axial cationic centers and an array of four equatorial H-bond donors pointing directly towards the center of the cavity. This precisely defined supramolecular environment is complementary to the geometry of classic octahedral complexes [M(XY)6 ] with six diatomic ligands. Very strong binding of [Pt(CN)6 ](2-) to the cage was observed, with the structure of the host-guest complex {[Pt(CN)6 ]@Pd2 L4 } supported by NMR spectroscopy, MS, and X-ray data. The self-assembled shell imprints its geometry on the encapsulated guest, and desymmetrization of the octahedral platinum species by the influence of the D4h -symmetric second coordination sphere was evidenced by IR spectroscopy. [Fe(CN)6 ](3-) and square-planar [Pt(CN)4 ](2-) were strongly bound. Smaller octahedral anions such as [SiF6 ](2-) , neutral carbonyl complexes ([M(CO)6 ]; M=Cr, Mo, W) and the linear [Ag(CN)2 ](-) anion were only weakly bound, showing that both size and charge match are key factors for high-affinity binding.
authors.affiliation: Research Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, 3217, Australia.|Institute for Inorganic Chemistry, Georg-August University Göttingen, Tammannstr. 4, 37077, Göttingen, Germany.|Faculty of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Str. 6, 44227, Dortmund, Germany.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Johnstone
authors.affiliation: Institute for Inorganic Chemistry, Georg-August University Göttingen, Tammannstr. 4, 37077, Göttingen, Germany.
authors.forename: Eike K
authors.initials: EK
authors.lastname: Schwarze
authors.affiliation: Max-Planck-Institute of Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Ahrens
authors.affiliation: Max-Planck-Institute of Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Schwarzer
authors.affiliation: Faculty of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Str. 6, 44227, Dortmund, Germany.
authors.forename: Julian J
authors.initials: JJ
authors.lastname: Holstein
authors.affiliation: Institute for Inorganic and Structural Chemistry, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany.
authors.forename: Birger
authors.initials: B
authors.lastname: Dittrich
authors.affiliation: Research Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, 3217, Australia. fred.pfeffer@deakin.edu.au.
authors.forename: Frederick M
authors.initials: FM
authors.lastname: Pfeffer
authors.affiliation: Institute for Inorganic Chemistry, Georg-August University Göttingen, Tammannstr. 4, 37077, Göttingen, Germany. guido.clever@tu-dortmund.de.|Faculty of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Str. 6, 44227, Dortmund, Germany. guido.clever@tu-dortmund.de.
authors.forename: Guido H
authors.initials: GH
authors.lastname: Clever
mesh_terms: D018360:Crystallography, X-Ray; D000067190:Exoskeleton Device; D008958:Models, Molecular
keywords: anion recognition; coordination cages; endohedral functionalization; host-guest chemistry; supramolecular chemistry