Ratiometric and near-infrared molecular probes for the detection and imaging of zinc ions.

The detection and imaging of Zn2+ in biological samples are of paramount interest owing to the role of this cation in physiological functions. This is possible only with molecular probes that specifically bind to Zn2+ and result in changes in emission properties. A "turn-on" emission or shift in the emission color upon binding to Zn2+ should be ideal for in vivo imaging. In this context, ratiometric and near-IR probes are of particular interest. Therefore, in the area of chemosensors or molecular probes, the design of fluorophores that allow ratiometric sensing or imaging in the near-IR region is attracting the attention of chemists. The purpose of this Focus Review is to highlight recent developments in this area and stress the importance of further research for future applications.