Lithium and sodium 3-(3,4-di-hydroxy-phen-yl)propenoate hydrate.

Treatment of 3-(3,4-di-hydroxy-phen-yl)propenoic acid (caffeic acid or 3,4-di-hydroxy-cinnamic acid) with the alkali hydroxides OH ( = Li, Na) in aqueous solution led to the formation of poly[aqua-[μ-3-(3,4-di-hydroxy-phen-yl)propenoato]lithium], [Li(CHO)(HO)], , and poly[aqua-[μ-3-(3,4-di-hydroxy-phen-yl)propenoato]sodium], [Na(CHO)(HO)], . The crystal structure of consists of a lithium cation that is coordinated nearly tetra-hedrally by three carboxyl-ate oxygen atoms and a water mol-ecule. The carboxyl-ate groups adopt a μ-κ :':' coordination mode that leads to a chain-like catenation of Li cations and carboxyl-ate units parallel to the axis. Moreover, the lithium carboxyl-ate chains are connected by hydrogen bonds between water mol-ecules attached to lithium and catechol OH groups. The crystal structure of shows a sevenfold coordination of the sodium cation by one water mol-ecule, two monodentately binding carboxyl-ate groups and four oxygen atoms from two catechol groups. The coordination polyhedra are linked by face- and edge-sharing into chains extending parallel to the axis. The chains are inter-linked by the bridging 3-(3,4-di-hydroxy-phen-yl)propenoate units and by inter-molecular hydrogen bonds to form the tri-periodic network.