Metal-coordination-mediated sequential chelation-enhanced fluorescence (CHEF) and fluorescence resonance energy transfer (FRET) in a heteroditopic ligand system

Abstract

Sequential fluorescence enhancement and fluorescence resonance energy transfer over a zinc ion gradient have been engineered in a two-fluorophore heteroditopic ligand platform. This is the first report that the strategies of metal-coordination modulated photoinduced electron transfer (PET), internal charge transfer (ICT), and fluorescence resonance energy transfer (FRET) are integrated in one synthetic fluoroionophore. Comparing to the previously reported single-fluorophore heteroditopic ligands (L. Zhang, R. J. Clark and L. Zhu, Chem. Eur. J. 2008, 14, 2894–2903), the resolution of two emission channels is greatly enhanced to almost 100 nm. This two-fluorophore heteroditopic platform lends promise to creating dual-emission fluorescent indicators where low- and high-target concentration regimes could be analyzed using independent emission filter sets.