HIGHLY BRANCHED FERROCENE-FUNCTIONALIZED POLYAZACYCLOALKANES AS ELECTROACTIVE RECEPTORS FOR TRANSITION-METAL IONS

Reaction of N,N',N '',N'''-tetrakis (2-aminoethyl)-1,4,8,11-tetraazacy clotetradecane (taec) with ferrocenecarbaldehyde and further reduction with LiAlH4 resulted in the synthesis of the redox-active receptor N, N',N enyl-3-azabutyl)-1,4,8,11-tetraazacyclotetradecane (tfabc); The p rotonation behaviour of tfabc and its complex formation with Cu-II, Zn -II and Cd-II have been studied in tetrahydrofuran-water (70:30 v/v) ( 0.1 mol dm(-3) NBu(4)(t)ClO(4), 25 degrees C). The potentiometric and electrochemical data indicate the formation of 1:1 and 1:2 (tfabc:M(2)) stoichiometries. The E(1/2) values for tfabc shift as a function of the pH from 389 (pH 10) to 482 mV (pH 2.5) and E(1/2) vs. pH curves f or the tfabc-H+-M(2+) systems (M = Cu, Zn or Cd) show that tfabc elect rochemically recognises the presence of copper(II) selectively at pH < 5. The shift of E(1/2) appears to be caused by electrostatic forces a nd the E(1/2) vs. pH curves can be predicted in terms of the distribut ion diagrams of the tfabc-H+-M(2+) systems.