Two-arm ferrocene amide compounds: synclinal conformations for selective sensing of dihydrogen phosphate ion.

[structure: see text] Ferrocene compounds bearing multiple amido groups selectively bind with the H(2)PO(4)(-) ion over other anions. The one-arm receptors form 1:1 complexes with the H(2)PO(4)(-) ion, whereas the two-arm receptors can accommodate two H(2)PO(4)(-) ions. The complexation modes and binding strengths are deduced from the NMR, calorimetry, fluorescence, and cyclic voltammetry studies. The two-arm ferrocene hexamide receptors likely exist in synclinal conformations to incorporate tetrahydrofuran molecules and H(2)PO(4)(-) ions.