Cryptand based fluorescence signaling systems for transition, inner-transition and main group metal ions: Modulation of the PET process through attachment of electron-withdrawing and electron donating groups

Abstract

The secondary amines present in the three bridges of a laterally non-symmetric aza-oxa cryptand have been partially substituted with anthryl groups to generate PET sensors in the format, fluorophore—spacer—receptor. Further, electron donating/withdrawing groups have been attached to the cryptand to modulate the PET process. A host of transition, inner-transition and heavy metal ions, when used as inputs, show fluorescence enhancement to different extents. The quantum yields of fluorescence emission have been rationalized with the structure of the overall systems.