Pyrene-Appended Fluorescent Tweezers Generated via the Weak-Link Approach and Their Halide Recognition Properties.

Through the Weak-Link Approach, fluorescent condensed and open Cu(I) tweezer complexes were prepared and characterized. These complexes exhibit fluorescence-sensitive binding properties for halide anions. The solid-state structure of a non-fluorescent Rh(I) tweezer analogue, determined by X-ray crystallography, shows that the counter anion, Cl(-), is trapped in between the two amide groups of the tweezer arms through hydrogen bonds. Although the tweezer binds Cl(-), the open complex also binds Cl(-), showing that the main role of the metal is to increase the local concentration of the pyrenyl amide moieties so that 2:1 binding can take place.