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.
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.
Boiocchi
Massimo
M
Dipartimento di Chimica Generale, Università di Pavia, via Taramelli 12, 27100 Pavia, Italy.
Bonizzoni
Marco
M
Fabbrizzi
Luigi
L
Foti
Francesco
F
Licchelli
Maurizio
M
Poggi
Antonio
A
Taglietti
Angelo
A
Zema
Michele
M