The Open Inorganic Chemistry Journal

2008, 2 : 80-89
Published online 2008 June 23. DOI: 10.2174/1874098700802010080
Publisher ID: TOICJ-2-80

Zn(II) Coordination by Open-chain Polyamine Ligands Containing Dipyridine Units. Highly Active Dinuclear Zn(II) Complexes in Phosphate Ester Hydrolysis

Carla Bazzicalupi , Andrea Bencini , Andrea Danesi , Enrico Faggi , Claudia Giorgi , Costanza Ravagli and Barbara Valtancoli
Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019-Sesto Fiorentino, Firenze, Italy.

ABSTRACT

The synthesis and characterization of two new open-chain ligands, L1 and L2, containing two 2,2’-dipyridine units connected respectively by a pentaethylenhexamine and a pentapropylenhexamine chain, is reported. Zn(II) complexation has been studied by means of potentiometric and UV-vis spectrophotometric measurements in aqueous solution. Both ligands form stable mono- and dinuclear complexes, the metal ions being coordinated by a single dipyridine unit and by the adjacent amine groups. The ability of the binuclear Zn(II) complexes as nucleophilic agents in hydrolytic processes has been tested by using bis(p-nitrophenyl) phosphate (BNPP) as substrate. Both complexes display high rate enhancements in BNPP cleavage in aqueous solution. The study outlines that different mechanisms are operative in BNPP cleavage in the presence of the L1 and L2 complexes.

Keywords:

Phosphate ester hydrolysis, macrocycles, zinc complexes.