Fluorescent sensors for diamines

A series of seven diamine sensors was prepared using dimers of a quinolone aldehyde chromophore. Binding to six different diamine guests was explored by a combination of NMR, absorption and fluorescence spectroscopy. It was shown that the dimeric sensors bound the diamine guests by formation of a bis-iminium ion which produced large changes in the fluorescence of the quinolone core. Issues of selectivity between guests are discussed.