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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
Author(s) -
Boiocchi Massimo,
Bonizzoni Marco,
Fabbrizzi Luigi,
Foti Francesco,
Licchelli Maurizio,
Poggi Antonio,
Taglietti Angelo,
Zema Michele
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200305717
Subject(s) - piperazine , cyclam , chemistry , ligand (biochemistry) , copper , fragment (logic) , stereochemistry , macrocyclic ligand , medicinal chemistry , crystallography , crystal structure , organic chemistry , receptor , metal , biochemistry , computer science , programming language
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.