Reactivity-Based Detection of Copper(II) Ion in Water: Oxidative Cyclization of Azoaromatics as Fluorescence Turn-On Signaling Mechanism

Citations Over TimeTop 1% of 2012 papers

Abstract

An oxidative cyclization reaction transforms nonemissive azoanilines into highly fluorescent benzotriazoles. We have found that introduction of multiple electron-donating amino groups onto a simple o-(phenylazo)aniline platform dramatically accelerates its conversion to the emissive polycyclic product. Notably, this chemistry can be effected by μM-level concentrations of copper(II) ion in water (pH = 6-8) at room temperature to elicit >80-fold enhancement in the green emission at λ(em) = 530 nm. Comparative kinetic and electrochemical studies on a series of structural analogues have established that the accelerated reaction rates correlate directly with a systematic cathodic shift in the oxidation onset potential of the azo precursors. In addition, single-crystal X-ray crystallographic analysis on the most reactive derivative revealed the presence of a five-membered ring intramolecular hydrogen-bonding network. An enhanced contribution of the quinoid-type resonance in such conformation apparently facilitates the mechanistically required proton transfer step, which, in conjunction with electron transfer at lower oxidation potential, contributes to a rapid cyclization reaction triggered by copper(II) ion in water.

Related Papers

• → Intramolecular Hydrogen Bond Interaction in Selected Diols(2003)17 cited
• → Poly(aniline boronic acid): A New Precursor to Substituted Poly(aniline)s(2001)25 cited
• → Intramolecular isotope effects in the reactions of CF32+ and CO22+ with HD(2001)28 cited
• → Nature of weak inter-and intramolecular interactions in crystals 8. Influence of intermolecular contacts on the strength of intramolecular O-H...N bonds in crystals of 3-(2-hydroxyphenyl)-1,2,4-triazoles(2006)3 cited
• → Stimulation intramolecular F⋯H hydrogen bond by intramolecular N → Si interaction in Si-fluoro derivatives of 8-mercaptoquinoline: DFT and MP2 calculations(2018)1 cited