Does a Reinforced Kinetic Macrocyclic Effect Exist? The Demetallation in Strong Acid of Copper(II) Complexes with Open and Cyclic Tetramines Containing a Piperazine Fragment |
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Authors: | Boiocchi Massimo Bonizzoni Marco Fabbrizzi Luigi Foti Francesco Licchelli Maurizio Poggi Antonio Taglietti Angelo Zema Michele |
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Institution: | Dipartimento di Chimica Generale, Università di Pavia, via Taramelli 12, 27100 Pavia, Italy. |
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Abstract: | The demetallation in acidic solution of the Cu(II) complexes with open-chain and cyclic tetramines containing a piperazine unit (2 and 3) has been investigated in terms of its kinetic aspects and compared with the behaviour of unsubstituted counterparts (tetramines 1 and 4). The presence of the piperazine fragment slows demetallation of the open-chain-ligand complex owing to the activation barrier associated with the conformational change from boat-to-half-boat; however, it does not affect the demetallation of the macrocyclic complex, which involves the spontaneous boat-to-twist conformational change. Thus, lateral reinforcement of a cyclam-like ligand does not add any further contribution to the typical inertness in demetallation of macrocyclic complexes. |
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Keywords: | conformational changes copper kinetics macrocycles piperazine |
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