Electrochemically active phenylenediamine probes for transition metal cation detection
Résumé
A novel family of tetraalkyl-p-phenylenediamine (TAPD)-based ligands has been efficiently prepared by reductive amination of heterocyclic aldehydes. The redox properties of these electrochemical active ligands change dramatically upon complexation of the transition metal cations Zn(2+), Ni(2+) and Cd(2+) leading to large oxidation potential shifts of up to 950 mV depending on the nature of the ligand. Complexes with a metal to ligand ratio of 1 : 2 were formed and (113)Cd NMR revealed an octahedral coordination sphere of the metal. All pyridyl derivatives show a distinct chemoselectivity (Zn(2+) > Cd(2+) > d Ni(2+)). The thiophenyl containing derivatives display a particularly high selectivity for zinc cations (Zn(2+) >> Ni(2+), Cd(2+)).