TY - JOUR
T1 - New terpyridine-containing macrocycle for the assembly of dimeric Zn(II) and Cu(II) complexes coupled by bridging hydroxide anions and π-stacking interactions
AU - Bazzicalupi, Carla
AU - Bencini, Andrea
AU - Berni, Emanuela
AU - Bianchi, Antonio
AU - Danesi, Andrea
AU - Giorgi, Claudia
AU - Valtancoli, Barbara
AU - Lodeiro, Carlos
AU - Lima, João Carlos
AU - Pina, Fernando
AU - Bernardo, M. Alexandra
PY - 2004/8/9
Y1 - 2004/8/9
N2 - The synthesis of the new terpyridine-containing macrocycle 2,5,8,11,14-pentaaza[15](6,6″)cyclo(2,2′:6′,2″) -terpyridinophane (L) is reported. The ligand contains a pentaamine chain linking the 6,6″ positions of a terpyridine unit. A potentiometric, 1H NMR, UV-vis spectrophotometric and fluorescence emission study on the acid-base properties of L in aqueous solutions shows that the first four protonation steps occur on the polyamine chain, whereas the terpyridine nitrogens are involved in proton binding only at strongly acidic pH values. L can form both mono- and dinuclear Cu(II), Zn(II), Cd(II), and Pb(II) complexes in aqueous solution. The crystal structures of the Zn(II) and Cd(II) complexes {[ZnLH]2(μ-OH)}(ClO4)5 (6) and {[CdLH] 2(μ-Br)}(ClO4)5·4H2O (7) show that two mononuclear [MLH]3+ units are coupled by a bridging anion (OH- in 6 and Br- in 7) and π-stacking interactions between the terpyridine moieties. A potentiometric and spectrophotometric study shows that in the case of Cu(II) and Zn(II) the dimeric assemblies are also formed in aqueous solution containing the ligand and the metals in a 1:1 molar ratio. Protonation of the complexes or the addition of a second metal ion leads to the disruption of the dimers due to the increased electrostatic repulsions between the two monomeric units.
AB - The synthesis of the new terpyridine-containing macrocycle 2,5,8,11,14-pentaaza[15](6,6″)cyclo(2,2′:6′,2″) -terpyridinophane (L) is reported. The ligand contains a pentaamine chain linking the 6,6″ positions of a terpyridine unit. A potentiometric, 1H NMR, UV-vis spectrophotometric and fluorescence emission study on the acid-base properties of L in aqueous solutions shows that the first four protonation steps occur on the polyamine chain, whereas the terpyridine nitrogens are involved in proton binding only at strongly acidic pH values. L can form both mono- and dinuclear Cu(II), Zn(II), Cd(II), and Pb(II) complexes in aqueous solution. The crystal structures of the Zn(II) and Cd(II) complexes {[ZnLH]2(μ-OH)}(ClO4)5 (6) and {[CdLH] 2(μ-Br)}(ClO4)5·4H2O (7) show that two mononuclear [MLH]3+ units are coupled by a bridging anion (OH- in 6 and Br- in 7) and π-stacking interactions between the terpyridine moieties. A potentiometric and spectrophotometric study shows that in the case of Cu(II) and Zn(II) the dimeric assemblies are also formed in aqueous solution containing the ligand and the metals in a 1:1 molar ratio. Protonation of the complexes or the addition of a second metal ion leads to the disruption of the dimers due to the increased electrostatic repulsions between the two monomeric units.
UR - http://www.scopus.com/inward/record.url?scp=4043076284&partnerID=8YFLogxK
U2 - 10.1021/ic049660l
DO - 10.1021/ic049660l
M3 - Article
AN - SCOPUS:4043076284
SN - 0020-1669
VL - 43
SP - 5134
EP - 5146
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 16
ER -