Attachment of Electron-Withdrawing 2,4-Dinitrobenzene Groups to a Cryptand-Based Receptor for Cu(II)/H⁺-Specific Exciplex and Monomer Emissions

In a cryptand-based fluorescent signaling system with the configuration “fluorophore−spacer−receptor”, attachment of the electron-withdrawing 2,4-dinitrobenzene groups to the cryptand receptor renders it highly selective for Cu(II). The system exhibits dual monomer and exciplex emissions in the presence of either of Cu(II) and H+ as input with concomitant movements of one of the 2,4-dinitrobenzene groups.