TY - JOUR
T1 - Coordination Chemistry of a New Cofacial Binucleating Macropolycycle Derived from 1,4,7-Triazacyclononane
AU - Tei, Lorenzo
AU - Arca, Massimiliano
AU - Aragoni, M. Carla
AU - Bencini, Andrea
AU - Blake, Alexander J.
AU - Caltagirone, Claudia
AU - Devillanova, Francesco A.
AU - Fornasari, Patrizia
AU - Garau, Alessandra
AU - Isaia, Francesco
AU - Lippolis, Vito
AU - Schröder, Martin
AU - Teat, Simon J.
AU - Valtancoli, Barbara
PY - 2003/12/29
Y1 - 2003/12/29
N2 - We have prepared and characterized a new phenol-based compartmental ligand (H2L) incorporating 1,4,7-triazacyclononane ([9]aneN3), and we have investigated its coordination behavior with CuII, Zn II, CdIII, and PbII. The protonation constants of the ligand and the thermodynamic stabilities of the 1:1 and 2:1 (metal/ligand) complexes with these metal ions have been investigated by means of potentiometric measurements in aqueous solutions. The mononuclear [M(L)] complexes show remarkably high stability suggesting that, along with the large number of nitrogen donors available for metal binding, deprotonated phenolic functions are also involved in binding the metal ion. The mononuclear complexes [M(L)] show a marked tendency to add a second metal ion to afford binuclear species. The formation of complexes [M2(H2L)] 4+ occurs at neutral or slightly acidic pH and is generally followed by metal-assisted deprotonation of the phenolic groups to give [M 2(HL)]3+ and [M2(L)]2+ in weakly basic solutions. The complexation properties of H2L have also been investigated in the solid state. Crystals suitable for X-ray structural analysis were obtained for the binuclear complexes [Cu2(L)](BF 4)2·1/2MeCN (1), [Zn2(HL)] (ClO 4)3·1/2MeCN (2), and [Pb2(L)](ClO 4)2·2MeCN (4). In 1 and 2, the phenolate O-donors do not bridge the two metal centers, which are, therefore, segregated each within an N5O-donor compartment. However, in the case of the binuclear complex [Pb2(L)](ClO4)2·2MeCN (4), the two PbII centers are bridged by the phenolate oxygen atoms with each metal ion sited within an N5O2-donor compartment of L2-, with a Pb⋯Pb distance of 3.9427(5) Å.
AB - We have prepared and characterized a new phenol-based compartmental ligand (H2L) incorporating 1,4,7-triazacyclononane ([9]aneN3), and we have investigated its coordination behavior with CuII, Zn II, CdIII, and PbII. The protonation constants of the ligand and the thermodynamic stabilities of the 1:1 and 2:1 (metal/ligand) complexes with these metal ions have been investigated by means of potentiometric measurements in aqueous solutions. The mononuclear [M(L)] complexes show remarkably high stability suggesting that, along with the large number of nitrogen donors available for metal binding, deprotonated phenolic functions are also involved in binding the metal ion. The mononuclear complexes [M(L)] show a marked tendency to add a second metal ion to afford binuclear species. The formation of complexes [M2(H2L)] 4+ occurs at neutral or slightly acidic pH and is generally followed by metal-assisted deprotonation of the phenolic groups to give [M 2(HL)]3+ and [M2(L)]2+ in weakly basic solutions. The complexation properties of H2L have also been investigated in the solid state. Crystals suitable for X-ray structural analysis were obtained for the binuclear complexes [Cu2(L)](BF 4)2·1/2MeCN (1), [Zn2(HL)] (ClO 4)3·1/2MeCN (2), and [Pb2(L)](ClO 4)2·2MeCN (4). In 1 and 2, the phenolate O-donors do not bridge the two metal centers, which are, therefore, segregated each within an N5O-donor compartment. However, in the case of the binuclear complex [Pb2(L)](ClO4)2·2MeCN (4), the two PbII centers are bridged by the phenolate oxygen atoms with each metal ion sited within an N5O2-donor compartment of L2-, with a Pb⋯Pb distance of 3.9427(5) Å.
UR - http://www.scopus.com/inward/record.url?scp=0345772327&partnerID=8YFLogxK
U2 - 10.1021/ic0345065
DO - 10.1021/ic0345065
M3 - Article
SN - 0020-1669
VL - 42
SP - 8690
EP - 8701
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 26
ER -