Intercalation of amino acid containing chiral dicarboxylic acid between Mg–Al layered double hydroxide
Layered double hydroxide (LDH) is a class of ionic lamellar solids with positively charged layers with two types of metallic cations and exchangeable hydrated gallery anions. The intercalation of organic anions, namely N,N′-(pyromellitoyl)-bis-l-α-amino acids diacid, into Mg–Al LDHs was studied for the first time. Chiral diacid monomers were synthesized in high yield from the reaction between pyromellitic dianhydride and different natural amino acids (l-isoleucine, S-valine, l-leucine, and l-phenylalanine) in refluxed acetic acid. The anion exchange appeared to be the most effective method; all examined organic anions were intercalated successfully by this way in Mg–Al host structures. The structures of supramolecular chiral materials were characterized using Fourier transform infrared spectroscopy, thermogravimetry analysis, X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy techniques. Thermogravimetry analysis results showed that there were five mass loss steps during the thermal decomposition of the hybrid materials. These optically active pillars create a chiral environment and they could be used in chiral field.