Neutral urea-based receptors for phosphates: synthesis and spectrophotometric studies

Article abstract of DOI:10.1016/j.tet.2016.09.042

A series of five fluorescent ligands (L1–L5) for anions were designed and synthesized. Urea, thiourea, and cyanoguanidine moieties were chosen as the binding groups, while 3,5-bis(trifluoromethyl)phenyl, coumarin, and BODIPY were used as the chromophores. The cyanoguanidines L3–L5 were promptly synthesized from corresponding thioureas using EDCI followed by reaction with cyanamide in the presence of triethylamine. The absorption and emission properties of the ligands L1–L5 were studied in CH₃CN; their coordination properties towards phosphate, pyrophosphate, and hydroxide anions, together with binding constants were evaluated.