Covalent grafting of copper–amino acid complexes onto chloropropylated silica gel—an FT-IR study

Cu(amino acid) complexes were immobilised on silica gel by covalent anchoring. The amino acids were l-histidine and l-tyrosine and their BOC—(tert-butoxycarbonyl) or methyl ester protected derivatives. To gain control over the synthesis the appropriately protected amino acid was reacted with chloropropylated silica gel first. This modified material as is, or after deprotecting the anchored amino acids, was used in further steps of building the immobilised Cu(II) complex. The covalently grafted complexes were studied by FT-IR spectroscopy and computer modelling. Materials containing protected histidine ligands showed catalase activity (decomposition of H2O2), those containing protected or unprotected tyrosine ligands displayed tyrosinase activity (the decomposed H2O2 oxidised the tyrosine skeleton to a quinoidal structure).