Herein, we present a ratiometric Zn2+ sensor comprising a fluorescent excited-state intramolecular proton transfer (ESIPT) material, 2-(2'-hydroxy-3-naphthyl)benzoxazole (HNBO), as a probe signaling unit and a phosphorescent iridium(III) complex, iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C2' ] picolinate (FIrpic), as a reference signaling unit, which are covalently linked thorough di-ether bridge. The probe signaling unit, HNBO, shows short-lived deep red fluorescence (?max = 656 nm, tobs = 0.68 ns) without Zn2+. As Zn2+ binds, this fluorescence is quenched and green fluorescence (?max = 549 nm, tobs = 7.83 ns) is increased, to give 12-fold increase in overall emission intensity. However, the reference signaling unit, FIrpic, shows invariant long-lived blue phosphorescence (?max = 470 nm, tobs = 0.05 �s) regardless of Zn2+ binding. ESIPT efficiently frustrates energy transfer between probe and reference unit because of its characteristic large Stoke's shift (~11000 cm-1). This molecular dyad which features embedded phosphorescent reference signal can overcome problematic concentration dependency of precedent chemosensors.

Ratiometric fluorescent zinc(II) ion sensor with built-in phosphorescent reference signaling unit

243rd National Meeting (2012)

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