An OFF-ON chemosensor for biological and environmental applications: sensing Cd2+ in water using catanionic vesicles and in living cellsElectronic supplementary information (ESI) available: Experimental methods and materials, synthesis of L1 and of [Cu4(L1)2](ClO4)2, absorption and emission spectra of L1 with all the metal ions, SAXS spectra, crystallographic tables, effect of the Cd2+ concentration on cells fluorescence. CCDC 949184. For ESI and crystallographic data in CIF or other electronic

A new OFF-ON fluorescent chemosensor ( L 1 ) for Cd 2+ recognition based on a 5-chloro-8-hydroxyquinoline pendant arm derivative of 1,4,7-triazacyclononane ([9]aneN 3 ) will be presented and its photochemical features in an MeCN-H 2 O 1 : 1 (v/v) mixture, in pure water, after inclusion within catanionic vesicles, and in living cells will be discussed. The coordination properties of L 1 both in solution and in the solid state were preliminarily studied and its selectivity towards Cd 2+ versus a set of different metal ions (Cu 2+ , Zn 2+ , Cd 2+ , Pb 2+ , Al 3+ , Hg 2+ , Co 2+ , Ni 2+ , Mn 2+ , Mg 2+ , K + , Ca 2+ , Ag + , and Na + ) was verified in MeCN-H 2 O 1 : 1 (v/v). In water, upon addition of increasing amounts of Cd 2+ to L 1 an enhancement of the fluorescence emission was detected. To overcome this serious drawback, L 1 was dissolved in an innovative catanionic vesicular solution based on sodium bis(2-ethylhexyl) sulfosuccinate, a traditional surfactant, and 1-dodecyl-3-methylimidazolium bromide, an ionic liquid. When enclosed within the vesicle bilayers in water, L 1 restored its fluorescence emission property upon addition of Cd 2+ . Remarkably, L 1 enters the cellular membrane of living cells thus allowing the detection of intracellular Cd 2+ . These findings encourage the application of this new fluorescent chemosensor in real samples for histological and environmental analyses. A new OFF-ON fluorescent chemosensor ( L 1 ) is able to recognize Cd 2+ in 1 : 1 MeCN-H 2 O (v/v), in pure water, after inclusion within catanionic vesicles, and living cells.