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

Anion receptor 1, a pyrene-functionalized tetrakis-(1 H-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.