5-Fluorosalicylic acid (CAS number 345-16-4), also known as 5-fluoro-2-hydroxybenzoic acid, has a fluorine substituent at 5-position and a hydroxyl group at 2-position. As an ortho-hydroxybenzoic acid, 5-fluorosalicylic acid is a good chelating agent. It forms highly fluorescent ternary complexes with terbium (Tb3+) that are employed in immunoassay. 5-Fluorosalicylic acid binds to copper (Cu2+) generating three isomers. Each isomer is formed predominantly depending on the pH value. Thus, 5-fluorosalicylic acid-copper complexes can be used for pH sensors. A flexible trifurcate titanium with 5-fluorosalicylic acid metalloligand can encapsulate silver nanoclusters in tetrahedral geometry. The metalloligand induces spatial growth and stability to the nanoclusters in non-linear optical and photoluminescent applications.
5-Fluorosalicylic acid is also used as a building block for active pharmaceutical ingredients (APIs) such as fluorinated deferasirox for chronic iron overload.