A highly selective ratiometric chemosensor for Hg2+ based on the anthraquinone derivative with urea groups

Anthraquinone derivatives with different substituents 1–3 were synthesized by introducing the urea group. Their cationsʹ binding properties were investigated by UV–vis absorption spectroscopy. Compared with 1 and 2, 3 with electron-withdrawing group (–NO2) showed a remarkable absorption change for Hg2+ over the other metal ions. The anthraquinone moiety and the N–H fragment of the urea moiety played key roles in sensing Hg2+. The different acidity of N–H fragments of the urea moiety, caused by electron push–pull properties of the substituents on the phenyl para position, is the main reason for recognition.