Anthraquinones as versatile colorimetric reagent for anions

Chemosensors are the molecule of abiotic origin that binds with different analyte by covalent or non-covalent interactions to create a change in colour or optical properties. In this context, colorimetric anion sensors are unique, because they detect target anions through visual detection with no sophisticated instrumentation technique. A chromophore or a fluorophore plays a significant role as a signalling unit in chemosensors. A variety of chemosensors designed with organic and inorganic chromophores or fluorophores used for the detection of various analytes. Among them anthraquinone has found significant application in anion recognition and sensing for their important role in various photochemical and colorimetric sensor systems. In this review we summarise the development of chromogenic anion sensors using colorimetric and fluorometric reagent anthraquinone as a signalling unit. We have attempted to cover almost all the reports of modified anthraquinone moiety as anion sensor reported until now.