Templated Synthesis of Copper(II) Azacyclam Complexes Using Urea as a Locking Fragment and Their Metal‐Enhanced Binding Tendencies towards Anions |
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Authors: | Massimo Boiocchi Dr Luigi Fabbrizzi Prof Mauro Garolfi Dr Maurizio Licchelli Prof Lorenzo Mosca Dr Cristina Zanini Dr |
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Institution: | 1. Centro Grandi Strumenti, Università di Pavia via Bassi, 27100 Pavia (Italy);2. Dipartimento di Chimica Generale, Università di Pavia via Taramelli 12, 27100 Pavia (Italy), Fax: (+39)?0382‐528544 |
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Abstract: | Copper(II) azacyclam complexes 3 2+ and 4 2+ were obtained through a metal‐templated procedure involving the pertinent open‐chain tetramine, formaldehyde and a phenylurea derivative as a locking fragment. Both metal complexes can establish interactions with anions through the metal centre and the amide NH group. Equilibrium studies in DMSO by a spectrophotometric titration technique were carried out to assess the affinity of 3 2+ and 4 2+ towards anions. While the NH group of an amide model compound and the metal centre of the plain CuII(azacyclam)2+ complex do not interact at all with anions, 3 2+ and 4 2+ establish strong interactions with oxo anions, profiting from a pronounced cooperative effect. In particular, 1) they form stable 1:1 and 1:2 complexes with H2PO4? ions in a stepwise mode with both hydrogen‐bonding and metal–ligand interactions, and 2) in the presence of CH3COO?, they undergo deprotonation of the amido NH group and thus profit from axial coordination of the partially negatively charged carbonyl oxygen atom in a scorpionate binding mode. |
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Keywords: | copper macrocyclic ligands receptors scorpionates template synthesis |
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