Pyrene-Linked Formylated Bis(dipyrromethane): A Fluorescent Probe for Dihydrogen Phosphate

Anion receptor 1, a pyrene-functionalized tetrakis-(1H-pyrrole-2-carbaldehyde), binds tetrabutylammonium dihydrogen phosphate in chloroform with high affinity over other test salts. Fluorescence quenching is seen upon the addition of H2PO4– to 1. The limit of detection (LOD) is ca. 46 nM. Anion binding in the solid state was confirmed via X-ray diffraction analysis, which revealed a sandwich-type complex, [1·3TBAH2PO4]2, wherein two separate molecules of 1 are linked via six dihydrogen phosphate anions bound in an S-like fashion.