Design of water-soluble lanthanide luminescent probes for the selective detection of HOCl

The synthesis and photophysical properties of tacn- or pyclen-based macrocyclic complexes featuring extended thioanisole-picolinate antennas are reported. These systems efficiently sensitize Eu(III) luminescence, whereas Tb(III) emission is quenched due to back-energy transfer (BET). In all lanthanide-containing complexes (Eu, Tb and Gd), the sulfide donor group was readily oxidized by HOCl to the corresponding sulfoxide or sulfone. Upon oxidation, the Tb(III) complexes became highly luminescent and act as OFF-ON probes when excited at the isosbestic point (302 nm). Finally, a water/buffer soluble Tb(III) complex combining ether and sulfide antenna was prepared, exhibiting remarkable sensitivity and selectivity towards HOCl detection.