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

Cu(amino acid) complexes were immobilised in montmorillonite 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.