We report combined IR spectroscopic and quantum mechanical studies on the interactions between hydrated proton (H 3 O ϩ and H 5 O 2 ϩ ) and polyethers (L = 15-crown-5, 18-crown-6, benzo-18-crown-6 and polyethylene glycols PEG-400 and PEG-600) in 1,2-dichloroethane (DCE) solution saturated with water, in the presence of non-coordinating chlorinated cobalt dicarbollide anions. The state of the hydrated proton and composition of the complexes are shown to depend on the nature and concentration of the ligand. Thus, 15-crown-5 forms [H 3 O ϩ ؒL] and [H 5 O 2 ϩ ؒ2L] complexes at small and high concentrations of L, respectively. At all studied concentrations, 18-crown-6 and benzo-18-crown-6 form only [H 3 O ϩ ؒL] type complexes, whereas PEGs form 1 : 1 complexes with H 5 O 2 ϩ . The coordination patterns of the hydrated proton depend on the topology, flexibility/rigidity and the number of donor centres of L. In thewith all 5 O-atoms of 15c5 via one linear and two asymmetric bifurcated H-bonds. We also report the first IR characterization of the [H 5 O 2 ϩ ؒ4H 2 O] cation complex in an organic solution. † Electronic supplementary information (ESI) available: the coordinates of the 6-31G* optimized systems (four files in PDB format). See
Extraction of strontium by synergistic mixtures of chlorinated cobalt dicarbollide (DCC) with different polyethers was studied. In the acidic media the distribution coefficients (Dsr) decreases in the order 15-crown-5 > PEG-400 > 18-crown-6 and does not correspond to the row of constants stability of the strontium complexes with these polyethers. When passing to the salt media (Li and Na nitrates) the row of Dsr is change: PEG-400 > 18 crown 6 > 15 crown 5.IR-spectroscopy study has shown that in synergistic mixtures the proton forms [HsO2+PEG], [HsO2+(15-crown-5)2] and [H30 § crown 6)] cations, which are exchange on Sr 2+ resulting to formation [Sr2+'PEG], [Sr2+'(15-crown-5)2] and [Sr2+(18-crown-6)(H20),] cations correspondingly. The PEG-400 is the best among polyethylene glycols, since its all six COC groups and two even more active OH groups complete the first co-ordination sphere of Sr 2 § Extremely low extractability of Sr 2+ from acidic media in the presence of 18-crown-6 as compared with 15-crown-5 is mainly caused by the high stability of the [H30+(18-crown-6)] cation that is responsible for less extractable hydrated Sr complex formation.
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