Aquated

Aquated is an adjective used primarily in chemistry to describe chemical species that are coordinated by water molecules or formed through hydration in an aqueous solution. A common context is a metal ion in water binding several water molecules, creating a hydrated or aqua complex such as [Fe(H2O)6]3+. The term also applies to reactions in which water replaces another ligand in a metal complex, a process known as aquation or ligand substitution by water.

In coordination chemistry and inorganic chemistry, aquation describes both the existence of aquated metal ions and the chemical steps where water acts as a ligand. Aquated species are central to understanding reactivity, ligand exchange, and reaction mechanisms in aqueous media. The number of coordinated water molecules can vary with the metal, its oxidation state, and the surrounding ligands, influencing properties like charge, geometry, and kinetic stability. Rates and equilibria of aquation depend on factors such as temperature, pH, and competing ligands.

A well-known practical example is the activation of certain metal-based drugs in physiological conditions. For instance, in the activation of some platinum anticancer agents, chloride ligands are replaced by water to form aqua species that can interact with biological targets. Aquation is also important in environmental chemistry, where the hydration state of metal ions affects mobility and bioavailability in water.

Etymology stems from aqua, meaning water, with the suffix -ated indicating a state or process. Related terms include hydration and aqua ligands.