Polymerization- and Solvent-Triggered Cooperativity Between Copper(II) Ions in the Catalysis of the Hydrolysis of Amino Esters by Pyridine-Based Ligands

✍ Scribed by Paolo Scrimin; Paolo Tecilla; Umberto Tonellato

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 697 KB
• Volume: 1998
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/(sici)1099-0690(199806)1998:6<1143::aid-ejoc1143>3.0.co;2-u

✦ Synopsis

Polymeric (2) and oligomeric (4, 5) materials made of repeating units of 2,6-diaminomethylpyridine and 4,4'diphenylmethane have been synthesized with the number of monomeric units (n) ranging from 2 to 29. In 1:1 DMSO/water solutions, these materials are fully soluble and strongly bind Cu II ions. The complexes catalyze to different extents the hydrolysis of the p-nitrophenyl esters of α-, β-, and γ-amino acids. Only Cu II complexes of polymeric 2 (n Ն 10) are more effective catalysts than free Cu II ions in the cleavage of βamino esters. Such enhanced reactivity, which in the case of β-alanine p-nitrophenyl ester (β-AlaPNP) amounts to almost two orders of magnitude when the comparison is made with the Cu II complex of monomeric ligand (N,N'-benzyl)-2,6aminomethylpyridine (3), is observed in 1:1 (v/v) DMSO/H 2 O only when a certain degree of polymerization is reached (6 Ͻ n Ͻ 10). In 1:1 (v/v) CH 3 CH 2 OH/H 2 O the kinetic benefits