A C2-symmetric ratiometric fluorescence and colorimetric anion sensor based on pyrrole derivative

A C2-symmetric fluorescence and colorimetric anion sensor (1) based on pyrrole derivative was designed and synthesized according to binding site-signaling subunit approach. The compound 1 was easily prepared by reaction of pyrrole-2,5-dicarboxaldehyde with 4-nitrophenylhydrazine in ethanol (yield=78%). In DMSO, the sensor 1 exhibited a visible color change from red to brown upon exposure to anions such as AcO− and F−; however, no obvious color changes were observed when the other tested anions (e. g. H2PO4−, Cl−, Br− and I−) were added. There was a significant redshift (Δλmax=160 nm) in UV–vis spectrum during UV–vis spectral titrations. In particular, the sensor 1 showed ratiometric fluorescence responses to anions.