Voltammetric metal cation sensors based on ferrocene derivatives with oxazoline and imine substituents

Ferrocene derivatives la, lb and 2 containing oxazoline substituents act as efficient voltammetric sensors of Mg2+ and Ca2+ ions in acetonitrile solut ion in concentrations as low as 10 mol%: a new redox peak appears in the cy clic voltammogram, positively shifted by 310-360 mV for 1a and 1b, and by 1 60-190 mV for 2, compared to E-1/2 of the free ligand. For the bisferroceny ldiimine derivative 3 the shift is 150-160 mV. Compounds la, lb and 3 are a lso responsive to Cu2+ ions (shifts of 250, 320 and 160 mV, respectively) a nd compound 3 is responsive to Zn2+ ions (150 mV shift) with no interferenc e from a large excess of several other metal salts. UV-vis spectrophotometr ic studies and H-1-NMR titration experiments confirm that the oxazoline or imine groups are the sites of metal complexation. (C) 2001 Elsevier Science B.V. All rights reserved.