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

[reaction: see text] 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.