3-py-TTF: Efficient and Simple Colorimetric Sensor for Copper Ion in Aqueous Solutions

Compound 1 shows remarkable sensing and coordinating properties only to Zn2+ ion, not to the other metal ions. Addition of a micromolar concentration of Zn2+ ion to the solution of 1, a dramatic change is observed in the UV–vis absorption spectrum and redox property, and the discrimination is readily possible even by “the naked eye.” Comparison of the recognition ability between 1 and its reference compound 2 suggests that the nature of the space linking tetrathiafulvalene and acceptor moiety plays an important role in the intramolecular charge-transfer state.