Formation of the second superhydrophobic shell around an encapsulated metal ion: synthesis, X-ray structure and electrochemical study of the clathrochelate and bis-clathrochelate iron and cobalt dioximates with ribbed perfluoroarylsulfide substituentsстатья
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Дата последнего поиска статьи во внешних источниках: 18 марта 2017 г.
Аннотация:The nucleophilic substitution of six chlorine atoms of the n-butylboron-capped clathrochelate iron and cobalt(II) precursors with perfluoroarylthiolate anions afforded the hexaperfluoroarylsulfide macrobicyclic iron and cobalt(II) tris-dioximates. The complexes obtained are soluble in aromatic and aliphatic hydrocarbons as well as in polar aprotonic solvents due to the presence of the superhydrophobic fluorine-containing molecular periphery. As it follows from the X-ray data for five iron and cobalt mono- and bis-clathrochelates, the geometry of their macrobicyclic frameworks is affected by both the nature of an encapsulated metal ion and that of the ribbed substituents. Bis-capping fragment CoIIO6 of the CoIIICoIICoIII bis-clathrochelate possesses a trigonal antiprismatic geometry, all the CoIIN6 coordination polyhedra are trigonal-prismatic, and those of the encapsulated iron(II) and cobalt(III) ions are intermediate between them. The wide range of Co–N distances as well as the significant shifts of the encapsulated cobalt(II) ions from the centres of their N6-coordination polyhedra were explained by the Jahn–Teller distortion. The EPR and magnetometry data are also characteristic of the low-spin cobalt(II) complexes with this distortion. The parameters of the 57Fe Mössbauer spectra of the iron macrobicycles are characteristic of the low-spin iron(II) complexes. The cyclic voltammograms (CVs) for the complexes studied contain the one-electron oxidation and reduction waves assigned to metal-centered redox-processes. The Fe2+/3+ and Co2+/3+oxidations are quasi-reversible or irreversible. The anionic clathrochelate species resulting from the reversible Co2+/+reductions are stable on the CV time scale, whereas their iron(I)-containing analogs are unstable.