Synthesis and electrochemical sensing behaviour of a new ferrocene functionalized tet ‘a’ macrocyclic receptor towards transition metal ions

Abstract A new ferrocene functionalized macrocyclic receptor 1,8‐bis(ferrocenylmethyl)‐5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane (R) has been designed and synthesized to study its potential application as chemosensor. The receptor has been characterized by spectral techniques and X‐ray diffraction. The compound crystallizes in the orthorhombic space group Pcab with four molecules in a unit cell (half‐a‐molecule in the asymmetric unit). The electrochemical studies of the receptor in dioxane–water (7:3 v/v, 25 °C) indicate that the receptor is pH‐dependent with a displacement of E1/2 to more anodic potentials with a decrease in the pH from 12 to 5. The electrochemical behaviour of R was also studied in the presence of Mn2+, Co2+, Ni2+, Cu2+ and Zn2+ in dioxane–water (7:3 v/v, 25 °C, [Bun4N][ClO4]), showing that upon complexation the ferrocene–ferrocenium half‐wave potential shifts anodically in relation to that of the free receptor. The maximum electrochemical shift (ΔE1/2) of 46 mV was found in the presence of Cu2+, followed by Co2+ (20 mV), Mn2+ (15 mV), Ni2+ (13 mV) and Zn2+ (9 mV). Moreover, the receptor R is able to electrochemically and selectively sense Cu2+ in the presence of the other transition metal cations studied. Copyright © 2007 John Wiley & Sons, Ltd.