Issue 20, 2012

Synthesis, structure, properties and immobilization on a gold surface of the monoribbed-functionalized tris-dioximate cobalt(ii) clathrochelates and an electrocatalytic hydrogen production from H+ ions

Abstract

The cycloaddition of the mono- and dichloroglyoximes to the cobalt(II) bis-α-benzyldioximate afforded the cobalt(II) mono- and dichloroclathrochelates in moderate yields (40–60%). These complexes undergo nucleophilic substitution of their reactive chlorine atoms with aliphatic amines, alcohols and thiolate anions. In the case of ethylenediamine and 1,2-ethanedithiol, only the macrobicyclic products with α,α′-N2- and α,α′-S2-alicyclic six-numbered ribbed fragments were obtained. The cobalt(II) cage complexes with terminal mercapto groups were synthesized using aliphatic dithiols. The crystal and molecular structures of the six cobalt(II) clathrochelates were obtained by X-ray diffraction. Their CoN6-coordination polyhedra possess a geometry intermediate between a trigonal prism and a trigonal antiprism, and the encapsulated cobalt(II) ions are shifted from their centres due to the structural Jahn–Teller effect with the Co–N distances varying significantly (by 0.10–0.26 Å). The electrochemistry of the complexes obtained was studied by cyclic voltammetry (CV). The anodic waves correspond to the quasi-reversible Co2+/3+ oxidations, whereas the cathodic ranges contain the quasi-reversibile waves assigned to the Co2+/+ reductions; all the cobalt(I)-containing clathrochelate anions formed are stable in the CV time scale. The electrocatalytic properties of the cobalt complexes obtained were studied in the production of hydrogen from H+ ions: the addition of HClO4 resulted in the formation of the same catalytic cathodic reduction Co2+/+ waves. The controlled-potential electrolysis with gas chromatography analysis confirmed the production of H2 in high Faraday yields. The efficiency of this electrocatalytic process was enhanced by an immobilization of the complexes with terminal mercapto groups on a surface of the working gold electrode.

Graphical abstract: Synthesis, structure, properties and immobilization on a gold surface of the monoribbed-functionalized tris-dioximate cobalt(ii) clathrochelates and an electrocatalytic hydrogen production from H+ ions

Supplementary files

Article information

Article type
Paper
Submitted
30 Dec 2011
Accepted
09 Mar 2012
First published
12 Mar 2012

Dalton Trans., 2012,41, 6078-6093

Synthesis, structure, properties and immobilization on a gold surface of the monoribbed-functionalized tris-dioximate cobalt(II) clathrochelates and an electrocatalytic hydrogen production from H+ ions

Y. Z. Voloshin, A. S. Belov, A. V. Vologzhanina, G. G. Aleksandrov, A. V. Dolganov, V. V. Novikov, O. A. Varzatskii and Y. N. Bubnov, Dalton Trans., 2012, 41, 6078 DOI: 10.1039/C2DT12513G

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