A Europium-based luminescent chemosensor for Zn2+ with quinoxaline as the antenna

A lanthanide-based luminescent probe [EuL] for Zn2+ was synthesized utilizing a DO3A ring as the Eu3+ chelator and a DPA moiety as the Zn2+ chelator. A quinoxaline functioned as both the linker and antenna. The two nitrogen atoms in quinoxaline are involved in the Eu3+ and Zn2+ binding, respectively. It gave an excitation at 336 nm for [EuL], which was longer than the reported values of this type of probes at present. Moreover, the titration studies provided a dissociation constant (Kd) of 55 nM for [EuL] while the competition investigation indicated that [EuL] had an affinity comparable to that of TPA (Kd 0.014 nM).