Detection of trace Cuii by a designed calix[4]arene based fluorescent reagent

Abstract

A highly Cu2+ selective calix[4]arene based fluorescent reagent, 5,17-bis(4-methylcoumarin-7-azo)-25,26,27,28-tetrahydroxycalix[4]arene, has been designed, synthesized and evaluated. The reagent exhibits excellent selectivity for Cu2+ over a wide range of alkali, alkaline earth and other transition metal ions. Quenching of its fluorescence due to a strong Cu2+ affinity, induced binding and selective redox reaction is not influenced by the presence of 20- to 10000-fold excesses of Al3+, Ca2+, Cd2+, Co2+, Cr3+, Hg2+, K+, Mg2+, Mn2+, NH4+, Ni2+, Pb2+, Zn2+, Cl−, NO3−, CO32−, SO42− or PO43−. Furthermore, with this fluorescent reagent a simple, sensitive and highly selective method has been developed for measuring trace Cu2+ in real biological fluids. The combination of multiple selective responses presented here may provide a useful design strategy for preparing selective reagents of other species.