Complexes of the H5O2+ and H3O+ cations with polyethers in water saturated dichloroethane solutions. A combined IR spectroscopic and quantum mechanics study

摘要

We report combined IR spectroscopic and quantum mechanical studies on the interactions between hydrated proton (H3O+ and H5O2+) 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 [H3O+.L] and [H5O2+.2L] complexes at small and high concentrations of L, respectively. At all studied concentrations, 18-crown-6 and benzo-18-crown-6 form only [H3O+.L] type complexes, whereas PEGs form 1 : 1 complexes with H5O2+. The coordination patterns of the hydrated proton depend on the topology, flexibility/rigidity and the number of donor centres of L. In the [H3O+.(18c6)], [H3O+.(B18c6)] and [H5O2+.2(15c5)] complexes, the hydrated proton forms preferentially O-H...O-L linear hydrogen bonds. In [H3O+.15c5], H3O+ interacts with all 5 O-atoms of 15c5 via one linear and two asymmetric bifurcated H-bonds. We also report the first IR characterization of the [H5O2+.4H(2)O] cation complex in an organic solution. [References: 41]