Caesium ion sequestration by a fluoro-metallocrown [16]-MC-8

Abstract

A fluoro-metallocrown selectively binds caesium, extracting it from aqueous solutions into an organic layer; the binding of Cs is monitored by (1)H-NMR of the paramagnetic complexes.

Heterometallic Rings: Their Physics and use as Supramolecular Building Blocks

“…[19] They can be made from 8-M compounds by adding cesium pivalate to the solution, and the primary ammonium is displaced by the alkali-metal cation to give [Cs][Cr 7 MF 8 (O 2 C t Bu) 16 ]( 9-M). [19] They can be made from 8-M compounds by adding cesium pivalate to the solution, and the primary ammonium is displaced by the alkali-metal cation to give [Cs][Cr 7 MF 8 (O 2 C t Bu) 16 ]( 9-M).…”

“…Solid-state 19 FNMR spectroscopy performed on single crystals of 2, 3-Ni,and 3-Cd has also been reported. [52] For 2, at low magnetic fields,asingle narrow resonance is seen at the Larmor frequency for 19 F, as expected because,o wing to symmetry,the <s i >= 0inthe S = 0ground state and there is no hyperfine interaction.…”

“…[52] For 2, at low magnetic fields,asingle narrow resonance is seen at the Larmor frequency for 19 F, as expected because,o wing to symmetry,the <s i >= 0inthe S = 0ground state and there is no hyperfine interaction. These factors make the different Fsites highly inequivalent and one result is that-despite the fact that the 19 Fn uclei are much closer to the electron spin density than 1 H-they are much less important in driving electron spin decoherence in Cr 7 M because this requires (near) equivalence between sites in nuclear spin "flip-flop" transitions. Thespectra for 3-Ni and 3-Cd are much more complicated because of the lower symmetry and the non-zero and uneven ground state <s i > .For example, 19 F nuclei bridging Cr···Cd or Cr···Cr edges experience hyperfine fields from one or two nearest neighbors,respectively.All the data can be modeled from the known <s i > distributions to determine the anisotropic hyperfine interactions arising from electron spin density at Cr and, for 3-Ni,atNi.…”

“…Thec ompound where M = Co (8-Co)i sp articularly useful as this allows us to show that the structures are maintained in solution. [19] Thef ast electron spin relaxation time of the Co II center allows paramagnetically shifted NMR spectra to be recorded on these heterometallic rings.I fw e compare 3-Co with 8-Co we can see the influence of the ammonium cation. For 3-Co we have a C 2 symmetry axis passing through Co and the Cr trans to it in the ring.…”

Chemical Engineering of Molecular Qubits

“…In addition to changes in alkyl chain length it has recently become possible to template Cr 7 Ni around Cs þ (100% 133 Cs, I ¼ 7 2 , H = Cs % 7:6) [32]. For both Piv and d-Piv compounds, there is little dependence on the central templating cation at 5 K (indicating that the bridging ligand nuclei dominate the relaxation) except in the dimethylammonium (Me 2 NH þ 2 ) case for which T m and x are reduced.…”