A novel squaraine dye with squaramide as a scaffold and the colorimetric detection of amine

A novel unsymmetrical squaramide-linked squaraine dye (SQ) has been synthesized through squaramide 3 and semisquaraine 6. The molecular structure of SQ has been characterized by 1H NMR, IR and MS. Due to the influence of the hydrogen bond and the solvent effect, SQ exhibits unique spectral properties compared with typical squaraine dyes. For its excellent ability of binding primary amine, SQ is a promising receptor of recognizing primary amine.