Lithium and sodium 3-(3,4-dihydroxyphenyl)propenoate hydrate

Abstract

Treatment of 3-(3,4-dihydroxyphenyl)propenoic acid (caffeic acid or 3,4-dihydroxycinnamic acid) with the alkali hydroxides MOH (M = Li, Na) in aqueous solution led to the formation of poly[aqua[μ-3-(3,4-dihydroxyphenyl)propenoato]lithium], [Li(C9H7O4)(H2O)] n , 1, and poly[aqua[μ-3-(3,4-dihydroxyphenyl)propenoato]sodium], [Na(C9H7O4)(H2O)] n , 2. The crystal structure of 1 consists of a lithium cation that is coordinated nearly tetrahedrally by three carboxylate oxygen atoms and a water molecule. The carboxylate groups adopt a μ3-κ3 O:O′:O′ coordination mode that leads to a chain-like catenation of Li cations and carboxylate units parallel to the b axis. Moreover, the lithium carboxylate chains are connected by hydrogen bonds between water molecules attached to lithium and catechol OH groups. The crystal structure of 2 shows a sevenfold coordination of the sodium cation by one water molecule, two monodentately binding carboxylate 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 b axis. The chains are interlinked by the bridging 3-(3,4-dihydroxyphenyl)propenoate units and by intermolecular hydrogen bonds to form the tri-periodic network.