TY - JOUR
T1 - Copper(II) and gallium(III) complexes of trans -Bis(2-hydroxybenzyl) cyclen derivatives
T2 - Absence of a cross-bridge proves surprisingly more favorable
AU - Esteves, Catarina V.
AU - Madureira, Joana
AU - Lima, Luís M P
AU - Mateus, Pedro
AU - Bento, Isabel
AU - Delgado, Rita
N1 - WOS:000335547400015
PY - 2014/5/5
Y1 - 2014/5/5
N2 - Two cyclen (1,4,7,10-tetraazacyclododecane) derivatives bearing trans-bis(2-hydroxybenzyl) arms, the 1,7-(2-hydroxybenzyl)-1,4,7,10- tetraazacyclododecane (H2do2ph) and its cross-bridged counterpart (H2cb-do2ph), have been synthesized, aiming toward the possible use of their copper(II) and gallium(III) complexes in nuclear medicine. The protonation of both compounds was studied in aqueous solution as well as their complexes with Cu2+ and Ga3+ cations. The complexes of both ligands with Ca2+ and Zn2+ metal ions were also studied due to the abundance of these cations in biological media. In mild conditions the complexes of Ca2+ and Ga3+ with H 2cb-do2ph did not form. The behavior of the two ligands and their complexes was compared by the values of the equilibrium constants, the data of varied spectroscopic techniques, the values of redox potentials of their copper(II) complexes, and the resistance of the complexes to acid dissociation. It was expected that, as found for related pairs of cyclen and cyclam (1,4,8,11-tetraazacyclotetradecane) derivatives, the cross-bridged macrocyclic derivative could be an excellent ligand for the complexation of copper(II). Additionally, the N-2-hydroxybenzyl groups were chosen due to their known ability to coordinate the gallium(III) cation. Due to the small size of the latter cation and its particular propensity to form hexacoordinate complexes, it was also expected that there would be a good ability of both ligands for the uptake of Ga3+. Surprisingly, the results revealed that the cyclen derivative H2do2ph is the best ligand for the coordination of Cu 2+ and Ga3+ cations, not only from their thermodynamic stability as expected but also from their kinetic inertness, when compared with its cross-bridged counterpart.
AB - Two cyclen (1,4,7,10-tetraazacyclododecane) derivatives bearing trans-bis(2-hydroxybenzyl) arms, the 1,7-(2-hydroxybenzyl)-1,4,7,10- tetraazacyclododecane (H2do2ph) and its cross-bridged counterpart (H2cb-do2ph), have been synthesized, aiming toward the possible use of their copper(II) and gallium(III) complexes in nuclear medicine. The protonation of both compounds was studied in aqueous solution as well as their complexes with Cu2+ and Ga3+ cations. The complexes of both ligands with Ca2+ and Zn2+ metal ions were also studied due to the abundance of these cations in biological media. In mild conditions the complexes of Ca2+ and Ga3+ with H 2cb-do2ph did not form. The behavior of the two ligands and their complexes was compared by the values of the equilibrium constants, the data of varied spectroscopic techniques, the values of redox potentials of their copper(II) complexes, and the resistance of the complexes to acid dissociation. It was expected that, as found for related pairs of cyclen and cyclam (1,4,8,11-tetraazacyclotetradecane) derivatives, the cross-bridged macrocyclic derivative could be an excellent ligand for the complexation of copper(II). Additionally, the N-2-hydroxybenzyl groups were chosen due to their known ability to coordinate the gallium(III) cation. Due to the small size of the latter cation and its particular propensity to form hexacoordinate complexes, it was also expected that there would be a good ability of both ligands for the uptake of Ga3+. Surprisingly, the results revealed that the cyclen derivative H2do2ph is the best ligand for the coordination of Cu 2+ and Ga3+ cations, not only from their thermodynamic stability as expected but also from their kinetic inertness, when compared with its cross-bridged counterpart.
UR - http://www.scopus.com/inward/record.url?scp=84899793001&partnerID=8YFLogxK
U2 - 10.1021/ic403156h
DO - 10.1021/ic403156h
M3 - Article
C2 - 24754354
AN - SCOPUS:84899793001
VL - 53
SP - 4371
EP - 4386
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 9
ER -