Until recently, there has been a great emergence of interests in
the development of fluorescent or colorimetric probes for various
metal cations and anions.1e7 Among them, transition metal ions
have especially received an increasing concern due to their importance
in many biological and environmental processes.8e10 In
particular, Cu2þ is a pivotal divalent cation, that is, utilized as
a catalytic cofactor for various metalloenzymes, including superoxide
dismutase, cytochrome c oxidase, tyrosinase, and nuclease.11
However, with excessive loading, copper ion can cause extremely
negative health effects such as gastrointestinal disturbance and
liver or kidney damage.12e15 Accordingly, considerable efforts have
been devoted to the development of fluorescent or colorimetric
Cu2þ-selective chemosensors