Cross-reactive binding versus selective phosphate sensing in an imine macrocycle sensor

Summary

We demonstrate a new approach to chemosensors suited for analysis of phosphate mixtures. Here, a combination of a cross-reactive receptor and an environmentally sensitive fluorophore allows for binding various phosphates and obtaining analyte-specific fluorescence response. We have investigated a flexible and cross-reactive imine-pyrrole macrocycle comprising both hydrogen-bond donors and acceptors, one that is capable of self-organizing in response to phosphate-type anions. This cross-reactive binding was elucidated by theoretical and nuclear magnetic resonance (NMR) studies. Incorporating an environmentally sensitive dansyl fluorophore, which responds to the presence of analytes with a varying degree of fluorescence amplification, resulted in translating the cross-reactive binding into variable analyte response and enabled differentiation of oxyanions. The trend of anion affinities is H₂PO₄⁻>AMP>H₂P₂O7²⁻>ADP>ATP. We show that only one sensor can differentiate among various phosphates including their mixtures. By applying machine learning algorithms, we were able to differentiate between 12 anions and accurately quantify ATP, ADP, AMP, PPi, Pi, and their mixtures.