Natural and synthetic receptors for nitrate anion

Synthetic receptors have been developed for anions such as chloride, phosphate, sulphate and carboxylate. Development of selective receptors for nitrate has, however, been more difficult. Theoretical calculations show that a six-coordinate geometry is the ideal geometry for coordinating NO3-. Crystallographic data show, however, that NO3- usually adopts a two- or three-coordinate geometry when interacting with receptors. In this review, we briefly discuss the role of NO3- in human health and its physical properties. We discuss how proteins and synthetic compounds bind NO3-, with an emphasis on crystal structures and calculations. Synthetic compounds that best mimic proteins in their types of non-covalent interactions are generally the most effective for binding NO3-.