Synthesis of an anthracene-based diguanidine and its recognition of carboxylic acids and phosphonic acids

Abstract

An anthracene-based diguanidine (1) for the recognition of carboxylic acids and phosphonic acids has been designed and synthesized. The diguanidine 1 forms 1:1 complexes with the dicarboxylic acids and diphosphonic acids in a DMSO solution, and the formation of the 1:1 complexes was determined by DOSY NMR spectroscopy. For the recognition of methylphosphonic acid (monophosphonic acid), the formation of the 1:2 complex was also determined. The diguanidine 1 shows a characteristic yellow fluorescence in a DMSO solution that may be caused by the weak aggregation of 1 which was estimated by dilution fluorescence studies. However, after the addition of the dicarboxylic acids (30 equiv.), the yellow fluorescence of 1 disappeared (turned off the fluorescence). On the other hand, after the addition of diphosphonic acids (1 equiv.) and methylphosphonic acid (2 equiv.), the yellow emission turned to purple. These fluorescence characteristics of the diguanidine 1 are also applicable for the detection of carboxylic acids and phosphonic acids.