Pyridinophane Platform for Stable Lanthanide(III) Complexation

详细信息    查看全文

• 作者：Goretti Castro ; Rufina Bastida ; Alejandro Mac铆as ; Paulo P茅rez-Lourido ; Carlos Platas-Iglesias ; Laura Valencia
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：May 20, 2013
• 年：2013
• 卷：52
• 期：10
• 页码：6062-6072
• 全文大小：469K
• 年卷期：v.52,no.10(May 20, 2013)
• ISSN：1520-510X

文摘

A detailed investigation of the solid state and solution structures of lanthanide(III) complexes with the macrocyclic ligand 2,11,20-triaza[3.3.3](2,6)pyridinophane (TPP) is reported. The solid state structures of 14 different Ln³⁺ complexes have been determined using X-ray crystallography. The ligand is coordinating to the Ln³⁺ ion by using its six nitrogen atoms, while nitrate or triflate anions and water molecules complete the metal coordination environments. The structure of the complexes in solution has been investigated by ¹H and ¹³C NMR spectroscopy, as well as by DFT calculations (TPSSh model) performed in aqueous solution. The structures obtained from these calculations for the complexes with the lightest Ln³⁺ ions (La鈥揝m) are in very good agreement with those determined by the analysis of the Ln³⁺-induced paramagnetic shifts. A structural change occurs across the lanthanide series at Sm³⁺; the complexes of the large Ln³⁺ ions (La鈥揘d) are chiral due to the nonplanar conformation of the macrocycle, and present effective C_3v symmetries in solution as a consequence of a fast interconversion of two enantiomeric forms with C₃ symmetry. The activation free energy for this enantiomerization process, as estimated by using DFT calculations, amounts to 33.0 kJ路mol^鈥?. The TPP ligand in the complexes of the heaviest Ln³⁺ ions (Eu鈥揕u) presents a half-chair conformation, which results in C_s symmetries in solution.