Copper amino-acid complexes - towards encapsulated metal centres

摘要

This article reports the synthesis of two novel amino-acid derivatives in which the side chain of glutamic acid (Glu) is coupled with different amines - tert-butylamine (ligand A) or a first generation 'Newkome' type dendron (ligand B). Consequently, ligand B possesses a bulkier branch than ligand A. Ligands A and B bind Cu2+ ions in solution, generating copper complexes A-Cu (M-r = 508) and B-Cu (M-r = 1077). These complexes were fully characterised and, in particular, have been investigated by electrochemical and electron spin resonance techniques to determine the extent of encapsulation of the copper ions. There were significant differences between the two complexes, indicating that Cu2+ may be more deeply encapsulated by ligand B and hence less able to interact with its surroundings. This indicates that metal ions can be sensitive reporters of even relatively small amounts of organic functionality, and emphasises the important role which protein superstructures can play in modulating the function of active metal ions. (C) 2004 Elsevier Ltd. All rights reserved.