Host-guest complexation of a fluorescent and electrochemical chemsensor for fluoride anion.

Host-guest complexation of a ferrocenenylphalene dyad 1, 1,1'-diaceylferrocenyl-3-hydroxyl-2-naphthoylhydrazone, as a fluorescent and electrochemical chemosensor for fluoride anion, was investigated. Crystal structure analysis revealed that the two naphthyl arms of compound 1 positioned in the same side about the ferrocene moiety and interacted through pi-pi stacking interactions. The intermolecular pi-pi stacking interactions and the C-H...pi interactions between the ferrocene moieties and the naphthalene rings linked the molecules together featuring a two-dimensional layered structure. Fluorescence titrations of compound 1 indicated that in the presence of F- and H2PO4-, the emission intensities enhanced significantly. Electrochemical titrations revealed that compound 1 sensed the F- anion in high selectivity with a cathodic shift of 120 mV, and had no sense in recognizing H2PO4- anion. 1H NMR titrations demonstrated that while compound 1 hydrogen-bonded to H2PO4- forming simple 1 : 1 host-guest complex, further addition of F- induced the deprotonation of compound 1.