An electrochemical study in acetonitrile of macrocyclic or open-chain ferrocene-containing oxa-aza or polyaza receptors in the presence of protons, metal cations and anions

摘要

Electrochemical studies on redox-active macrocyclic and open-chain ferrocene-containing oxa-aza or polyaza receptors were carried out in acetonitrile in the presence of protons, cations and anions. Electrochemical studies in the presence of H~+, Ni~(2+), Cu~(2+), Zn~(2+), Cd~(2+), Hg~(2+) and Pb~(2+) with L~4 (1,15-diferrocenyl-2,5,8,11,14-pentaazapentadecane) and L~5 (1,4,7,10,13-penta(ferrocenylmethyl)-1,4,7,10,13-pentaazacyclopentadecane) resulted in shift of the ferrocene oxidation wave to more positive potentials with maximum shifts for L~4 in the presence of Zn~(2+) and for L~5 in the presence of Ni~(2+), Cu~(2+) and Hg~(2+) of 80 mV. In contrast, L~1 (10-ferrocenylmethyl-1,4,7-trioxa-10-azacyclododecane), L~2 (1,8-bis[bis(ferrocenylmethylamino)]-3,6-dioxaoctane) and L~3 7,13-bis(ferrocenylmethyl)-1,4,10-trioxa-7,13-diazacyclopentadecane) show a two-wave behaviour for H~+, Pb~(2+) and Hg~(2+) allowing the amperometric titration of these metal cations. The maximum oxidation peak shift of 290 mV was found for L~1 in the presence of Hg~(2+). Electrochemical behaviour with anions (H_2PO_4~-, HSO_4~-, Br~- and cl~-) in acetonitrile show that L~2 and L~6 (1,8-bis(ferrocenylmethylamino)-3,6-dioxaoctane) electrochemically sense H_2PO_4~-. For L~2 a cathodic shift of the oxidation peak of 190 mV and a shift of 346 mV to lower potential for the reduction peak was found. L~6 shows a similar behaviour. This electrochemical sense of H_2PO_4~- was observed even in the presence of excess of other anions (HSO_4~- or Cl~-) in anion competition experiments.