Zinc (Hydrogen-β-glutamate)-chloride Hydrate [Zn (β-GluH)Cl(H2O)], a One-dimensional Coordination Polymer

Aspartes and α-glutamates of the alkali (Li, Na, K) and alkaline earth metals (Mg, Ca) are important components for many preparations in the pharmaceutical industry [1]. L-aspartic and L-α-glutamic acid in particular, which are ubiquitous in nature, have been shown to form a large variety of salts and complexes with these metals both in aqueous solution and in the solid state depending on the pH of the system. This coordination chemistry is of prime importance for many areas of Bioinorganic Chemistry in general, and for biomineralization in particular, and this relevance is responsible for the therapeutic and diagnostic value of the compounds. In their complexes, aspartic or α-glutamic acid may appear as monoor dianions [L-AspH]−, [LAsp]2−, [L-α-GluH]−, and [L-α-Glu]2−, functioning as counterions or as potentially multidentate donor ligands. Particularly advantageous therapeutical effects have been demonstrated for formulations where the aspartate or glutamate anions are combined with other anions such as chloride, as in [Mg(LAspH)]Cl(H2O)3 [2]. Trace metals like zinc have also been included into recent investigations and the stoichiometry and structures of several α-aspartates and -glutamates are documented [3 – 5]. Apart from standard binary compounds, a mixed-ligand complex [Zn(L-AspH)Cl] was obtained and shown to be a twodimensional coordination polymer [6]. The coordination chemistry of β -amino acids, which are rare in nature, is much less developed and