Anchoring copper–amino acid complexes on silica or in montmorillonite - an FT-IR study

Cu(amino acid) complexes were immobilised in mommorillonite or on silica gel by two methods (i) cation exchange first followed by ligation (two-step method) or (ii) depositing the ligands onto/into the support, then introducing the metal ion and, finally, filling the empty coordination sites of the central ions by added ligands (three-step method). The amino acids were L-tyrosine, L-histidine or L-aspartic acid. Immobilisation was followed by infrared spectroscopy. Host-guest substances were formed in every Cu2+- amino acid- montmorillonite system, however, significant anchoring occurred on silica gel only when tyrosine was the ligand. The heat stabilities of these host-guest substances were appreciable, complete decomposition only occurred at 673 K. (C) 2003 Elsevier Science B.V. All rights reserved.
Keyword: host-guest substances,anchoring,Na-montmorillonite,FT-IR spectroscopy,silica gel,immobilisation,heat stability,Cu(ammo acid) complexes