solvate

A solvate is a chemical compound in which solvent molecules are incorporated into another substance through the process of solvation. The two common contexts are crystallography, where solvent molecules occupy positions in the crystal lattice (solvent of crystallization), and coordination chemistry, where solvent molecules act as ligands bound to a central metal atom or ion in a complex. The term can also describe a solution species that is surrounded by solvent molecules, known as solvation in solution chemistry, though in that sense the focus is on solvent–solute interactions rather than a fixed solid structure.

In crystallography, a solvate forms when solvent molecules are included in a definite ratio with the solute, producing a crystalline material whose formula reflects both components. Hydrates are solvates in which the solvent is water. Other solvates may involve organic solvents such as methanol, ethanol, or acetonitrile. The solvent molecules in a crystal lattice may be removable by heating or alternate crystallization, yielding an anhydrous or desolvated form, though this can alter properties like stability and solubility.

In coordination chemistry, a solvate refers to a metal complex in which solvent molecules are directly coordinated to the metal center, forming part of the coordination sphere. Classic examples include six-coordinate aqua complexes such as [Fe(H2O)6]2+ or solvated organometallics where solvent ligands influence reactivity and geometry.

Solvates are important in fields ranging from crystallography and solid-state chemistry to pharmaceuticals, where the presence or absence of solvent molecules can affect solubility, stability, and patent considerations.