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

Abstract

Caffeic acid (3,4-dihydroxycinnamic acid) was reacted with lithium and sodium hydroxides in aqueous solution to yield crystalline polymeric hydrate salts. In the lithium compound, each Li cation adopts a near-tetrahedral geometry coordinated by three carboxylate oxygen atoms and one water molecule; the carboxylate groups bridge Li centers in a chain-like arrangement along one crystallographic axis, with additional hydrogen bonding between coordinated water and catechol hydroxyl groups. In the sodium compound, the Na cation is sevenfold-coordinated by one water molecule, two monodentate carboxylate groups, and four catechol oxygen atoms. Face- and edge-sharing of coordination polyhedra generates chains that are further interconnected through bridging propenoate ligands and intermolecular hydrogen bonds, producing a three-dimensional network structure.