Fluorescent Discrimination of Primary Alkyl Amines by Using a Binaphthyl Ladder Polymer

A 1,1-binaphthyl-based ladder polymer containing fused polyaromatic rings and aldehyde groups in its repeating units has been synthesized. In the presence of primary aliphatic amines, this polymer shows fluorescence enhancement at lambda = 655 nm with a significant red shift from its original emission wavelength at lambda = 585 nm. However, neither fluorescence enhancement nor shift of the emitting wavelength was observed when the polymer was treated with secondary and tertiary amines as well as with an aromatic amine. Thus, this ladder polymer can be used to selectively recognize primary aliphatic amines with ratiometric detection. The fluorescence response of the ladder polymer is also very different from its precursor polymer as well as its monomeric analogue, which do not show fluorescence enhancement towards primary amines.