Modulating the Sensor Response to Halide Using NBD-Based Azamacrocycles

Ligand L (2,6-bis([7-(7-nitrobenzo[1,2,5]oxadiazole-4-yl)-3,10-dimethy1-1,4,7,10-tetraazacyclododeca-1-yl]methyl}phenol) is a fluorescent sensor that is useful for detecting Cu(II), Zn(II), and Cd(II). Some of the complexes formed are able to sense the presence of halides in solution. L passes through the cellular membrane, becoming fluorescent inside cells. The H-1L- species is able to form dinuclear complexes with [M2H-1L](3+) stoichiometry with Cu(II), Zn(II), and Cd(II) ions, experiencing a CHEF effect upon metal coordination in an acetonitrile/water 95:5 (v/v) solution. In all three of the complexes investigated, the metal cations are coordinatively unsaturated and can therefore bind secondary ligands as anionic species. The crystal structure of [Cd-2(H-1L)Cl-2](ClO4)center dot 4H(2)O is discussed. The Zn(II) complex behaves as an OFF-ON sensor for fluoride and chloride anions.