Di- and trinuclear arrangements of zinc(II)-1,5,9-triazacyclododecane units on the calix[4]arene scaffold: Efficiency and substrate selectivity in the catalysis of ester cleavage

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Cacciapaglia, Roberta and Casnati, Alessandro and Mandolini, Luigi and Reinhoudt, David N. and Salvio, Riccardo and Sarton, Andrea and Ungaro, Rocco (2007) Di- and trinuclear arrangements of zinc(II)-1,5,9-triazacyclododecane units on the calix[4]arene scaffold: Efficiency and substrate selectivity in the catalysis of ester cleavage. Inorganica Chimica Acta, 360 (3). pp. 981-986. ISSN 0020-1693

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Abstract:The catalytic activity of the zinc(II) complexes of calix[4]arenes decorated with 1,5,9-triazacyclododecane ligands at the 1,2-, 1,3-, and 1,2,3-positions of the upper rim was investigated in the basic methanolysis (pH 10.4) of aryl acetates functionalised at the meta- and para-positions with a carboxylate anchoring group. Michaelis–Menten kinetics and turnover catalysis were observed. High rate accelerations, up to more than 104-fold at 0.2 mM catalyst, were recorded in the most favourable catalyst–substrate combinations. The order of catalytic efficiency of regioisomeric bimetallic complexes is 1,2-vicinal 1,3-distal, resulting from a significant degree of synergism between metal ions in the former, and a complete lack in the latter. The moderately higher efficiency of the trimetallic compared with the 1,2-vicinal bimetallic catalyst provides an indication of a possible cooperation of three zinc(II) ions in the catalysis.

Item Type:Article
Copyright:© 2006 Elsevier B.V.
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Link to this item:http://purl.utwente.nl/publications/74935
Official URL:http://dx.doi.org/10.1016/j.ica.2006.07.024
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Metis ID: 241410