Nitrophenylfuran-benzimidazole-based reversible alkaline fluorescence switch accurately controlled by pH

Abstract

Two colorimetric and fluorescent pH chemosensors L4 and L5 bearing benzimidazole moiety as pH sensing site and nitrophenylfuran moiety as signal group were designed and synthesized. L4 and L5 showed well reversible pH response for a specific pH change in narrow pH range (at pH ranged from 11.0 to 12.0) through obvious fluorescent color changes. Common anions (such as F−, Cl−, Br−, I−, AcO−, H2PO4−, HSO4−, ClO4−, CN−) and cations (such as Fe3+, Hg2+, Ag+, Ca2+, Cu2+, Zn2+, Pb2+, Cd2+, Ni2+, Co2+, Cr3+, Mg2+) did not interfere with the pH response process. These properties make L4 and L5 act as accurate pH controlled alkaline fluorescence switches.