Anion Sensing in Aqueous Media by Photo-active Transition Metal Bipyridyl Rotaxanes

A chloride anion templation methodology is utilized in the construction of novel transition-metal rheni(I) and rutheni(II) bipyridyl appended [ 2] rotaxanes. H-1 NMR spectroscopic titrations reveal the ability of the rotaxanes to selectively bind chloride over the more basic oxoanions, with the ruthenium(II) bipyridyl appended rotaxane strongly binding chloride in 30% water. Photophysical in-vestigations demonstrate the ability of the rotaxanes to sense anions in aqueous media, with chloride being selectively complexed, in general agreement with NMR spectroscopy determined anion binding data.