Fluorescent Sensor for Copper(II) and Cyanide Ions via the Complexation–Decomplexation Mechanism with Di(bissulfonamido)spirobifluorene

[Image: see text] A novel spirobifluorene derivative bearing two bissulfonamido groups is successfully synthesized by Sonogashira coupling. This compound exhibits a strong fluorescence quenching by Cu(II) ion in a 50% mixture between acetonitrile and 20 mM pH 7.0 N-(2-hydroxyethyl)piperazine-N′-ethanesulfonic acid (HEPES) buffer with a detection limit of 98.2 nM. However, this sensor also shows ratiometric signal shifts from blue to yellow in the presence of Zn(II), Pb(II), and Hg(II) ions. The static quenching mechanism is verified by the signal reversibility using ethylenediaminetetraacetic acid (EDTA) and the Stern–Volmer plots at varying temperatures. The Cu(II)–spirobifluorene complex shows a highly selective fluorescence enhancement upon the addition of CN(–) ion with the detection limit of 390 nM. The application of this complex for quantitative analysis of spiked CN(–) ion in real water samples resulted in good recoveries.