There is an increasing interest in the development of a new generation
of molecules for the sensing of target chemical species of
environmental or biological interest. Among them, chromogenic
receptors are especially attractive because the recognition process
is accomplished with an easy-to-detect perceptible color evolution.
Significant efforts have been carried out in the last years for understanding
the theoretical basis of the chromogenic guest recognition
and a number of selective chemosensors for anions, cations, and
neutral species have been designed and synthesized