A molecular chemodosimeter to probe "closed shell" ions in kidney cells

Two quinidine-functionalized coumarin molecular probes have been synthesized and have been found to bind metal cations (Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Hg²⁺, Ni²⁺, and Zn²⁺) with high affinity in organic-aqueous media (DMSO-HEPES). The chemodosimeters coordinate with the Zn²⁺ ions in a two-to-one ratio (molecular probe : Zn²⁺) with a log β of 10.0 M^-2. Upon the addition of the closed-shell metal ions studied, a fluorescence turn-on via an excimer formation is seen at 542 nm due to the quinaldine moiety adopting a syn arrangement when coordinated to the metal Zn²⁺ ions. Confocal microscopy monitored free Zn²⁺ ions in the Human Embryonic Kidney cell line HEK293 by coordinating with the chemodosimter.