1115-63-5Relevant articles and documents
Metal Ion Binding by Amino Acids. - Preparation and Crystal Structures of Lithium Hydrogen L-Aspartate Hydrate and Potassium Hydrogen L-Aspartate Dihydrate
Schmidbaur, Hubert,Bach, Ina,Wilkinson, Dallas L.,Mueller, Gerhard
, p. 1427 - 1432 (2007/10/02)
Lithium hydrogen L-aspartate, prepared by neutralisation of lithium carbonate with aqueous L-aspartic acid L-AspH2, crystallizes as the monohydrate Li(L-AspH) * H2O.Saturated solutions show pH 7.30.Potassium hydrogen L-aspartate, synthesized similarly from L-AspH2 and KOH, crystallizes from aqueous solutions (pH 7.52) as the dihydrate K(L-AspH) * 2 H2O.The NMR spectra of the two complexes exhibit no major differences. - Crystalline Li(L-AspH) * H2O has a layer structure, in which each lithium atom is in a tetrahedral environment of four oxygen atoms belonging to four different amino acids.The hydrate water molecule and the nitrogen function (protonated to give an ammonium center) have no metal contacts, but are components of a network of hydrogen bonds interconnecting the layers.One of the carboxylate oxygen atoms is in a bridging position between the metal atoms, which are arranged in pairs and participate in edge-sharing six-membered rings.In each of the layers large empty channels are formed. - Crystals of K(L-AspH) * 2 H2O show a chain structure with the potassium atoms exhibiting coordination number 7.The metal atoms are again arranged in double strings with the β-carboxylate oxygen atoms of the L-AspH(1-) counter anions in chelating and bridging positions.The α-carboxylate and protonated amino functions show no metal contacts, but are part of the hydrogen-bonding system interconnecting the chains of the coordination polymer.Both hydrate water molecules are K-coordinated, one in a metal-bridging position. - Keywords: L-Aspartate complexes / Lithium hydrogen L-aspartate hydrate / Potassium hydrogen L-aspartate dihydrate / Amino acid complexes
