Investigating the Complexation of the Pb2+/Bi3+ Pair with Dipicolinate Cyclen Ligands

详细信息    查看全文

• 作者：Lu铆s M. P. Lima ; Maryline Beyler ; Rita Delgado ; Carlos Platas-Iglesias ; Rapha毛l Tripier
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：July 20, 2015
• 年：2015
• 卷：54
• 期：14
• 页码：7045-7057
• 全文大小：703K
• ISSN：1520-510X

文摘

The complexation properties toward Pb²⁺ and Bi³⁺ of the macrocyclic ligands 6,6鈥?((1,4,7,10-tetraazacyclododecane-1,7-diyl)bis(methylene))dipicolinic acid (H₂do2pa) and 6,6鈥?((4,10-dimethyl-1,4,7,10-tetraazacyclododecane-1,7-diyl)bis(methylene))dipicolinic acid (H₂Me-do2pa) have been investigated. A new three-step synthesis of H₂do2pa following the bisaminal methodology has also been developed. The X-ray structures of [Pb(Me-do2pa)]路6H₂O and [Bi(Me-do2pa)](NO₃)路H₂O show that the two metal ions are eight-coordinated by the ligand. The two complexes exist as the racemic 螖(未未未未)/螞(位位位位) mixture both in the solid state and in solution, as indicated by NMR and DFT studies. The stability constants of the lead(II) and bismuth(III) complexes of the two ligands were determined in 0.5 M KCl using potentiometric and spectrophotometric techniques. The stability constants determined for the complexes of Pb²⁺ are relatively high (log K_ML = 16.44 and 18.44 for H₂do2pa and H₂Me-do2pa, respectively) and exceptionally high for the complexes of Bi³⁺ (log K_ML = 32.0 and 34.2 for H₂do2pa and H₂Me-do2pa, respectively). The [Pb(Me-do2pa)] complex presents rather fast formation and very good kinetic inertness toward transchelation. Additionally, the [Bi(Me-do2pa)]⁺ complex was found to present a remarkably fast complexation rate (full complexation in 鈭? min at pH 5.0, acetate buffer) and a very good kinetic inertness with respect to metal ion dissociation (half-life of 23.9 min in 1 M HCl), showing promise for potential applications in 伪-radioimmunotherapy.