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Download fileCoordination Chemistry of a Molecular Pentafoil Knot
dataset
posted on 11.02.2019, 00:00 authored by Liang Zhang, Alexander J. Stephens, Jean-François Lemonnier, Lucian Pirvu, Iñigo J. Vitorica-Yrezabal, Christopher J. Robinson, David A. LeighThe binding of Zn(II) cations to
a pentafoil (51) knotted
ligand allows the synthesis of otherwise inaccessible metalated molecular
pentafoil knots via transmetalation, affording the corresponding “first-sphere”
coordination Co(II), Ni(II), and Cu(II) pentanuclear knots in good
yields (≥85%). Each of the knot complexes was characterized
by mass spectrometry, the diamagnetic (zinc) knot complex was characterized
by 1H and 13C NMR spectroscopy, and the zinc,
cobalt, and nickel pentafoil knots afforded single crystals whose
structures were determined by X-ray crystallography. Lehn-type circular
helicates generally only form with tris-bipy ligand strands and Fe(II)
(and, in some cases, Ni(II) and Zn(II)) salts, so such architectures
become accessible for other metal cations only through the use of
knotted ligands. The different metalated knots all exhibit “second-sphere”
coordination of a single chloride ion within the central cavity of
the knot through CH···Cl– hydrogen
bonding and electrostatic interactions. The chloride binding affinities
were determined in MeCN by isothermal titration calorimetry, and the
strength of binding was shown to vary over 3 orders of magnitude for
the different metal-ion–knotted-ligand second-sphere coordination
complexes.