Bravard Florence, Bretonnière Yann, Wietzke Raphaël, Gateau Christelle, Mazzanti Marinella, Delangle Pascale, Pécaut Jacques
Laboratoire de Reconnaissance Ionique, Département de Recherche Fondamentale sur la Matière Condensée, Service de Chimie Inorganique et Biologique (FRE 2600), CEA-Grenoble, 38054 Grenoble, Cedex 09, France.
Inorg Chem. 2003 Dec 1;42(24):7978-89. doi: 10.1021/ic034692e.
The synthesis of the potentially heptadentate ligand tris[6-((2-N,N-diethylcarbamoyl)pyridyl)methyl]amine, tpaam, containing three pyridinecarboxamide arms connected to a central nitrogen is described. Lanthanide complexes of this ligand are prepared and characterized. The crystallographic structure of the complexes of three lanthanide ions (La, Nd, Lu) is determined. The lanthanide(III) complexes of tpaam crystallize as monomeric species (in the presence of chloride or iodide counterions) in which the ligand tpaam acts as a N4O3 donor. The crystal structures presented here show that the Ln[bond]O and Ln[bond]N(pyridyl) distances in the complexes of tpaam are similar to those found for the tpaa complexes (H(3)tpaa = alpha,alpha',alpha' '-nitrilotri(6-methyl-2-pyridinecarboxylic acid) despite the difference in charge. A lengthening of the Ln[bond]N(apical) distance is observed in the tpaam complexes compared to the tpa (tris[(2-pyridyl)methyl]amine) complexes which is more marked for larger lanthanides than for smaller ones. The solution structures of the tpaam complexes were analyzed across the 4f series and compared to the solution structures of the lanthanide complexes of the tetradentate ligand tpa. Proton NMR studies are in agreement with the presence of C(3)(v) symmetric solution species for both ligands. For the larger lanthanides, the cation moves away from the apical nitrogen compared to the position occupied in tpa complexes, whereas for the smaller lanthanides, the metal ion is located in a similar position for the two ligands. Quite surprisingly, the formation constant of the Eu(tpaam)Cl(3) complex in D(2)O at 298 K (log beta(110) = 2.34(4)) is very similar to the one reported for Eu(tpa)Cl(3) (log beta(110) = 2.49(4) at 298 K in D(2)O) indicating that the addition of three amide groups to the ligand tpa does not lead to any increase in stability of the lanthanide complexes of tpaam compared to those of tpa.
本文描述了潜在的七齿配体三[6-((2-N,N-二乙基氨基甲酰基)吡啶基)甲基]胺（tpaam）的合成，该配体含有连接至中心氮原子的三个吡啶甲酰胺臂。制备并表征了该配体的镧系元素配合物。测定了三种镧系离子（La、Nd、Lu）配合物的晶体结构。tpaam的镧系（III）配合物以单体形式结晶（在存在氯离子或碘离子抗衡离子的情况下），其中配体tpaam作为N4O3供体。此处给出的晶体结构表明，尽管电荷不同，但tpaam配合物中的Ln—O和Ln—N（吡啶基）距离与tpaa配合物（H(3)tpaa = α,α',α''-次氮基三(6-甲基-2-吡啶羧酸)）中的类似。与tpa（三[(2-吡啶基)甲基]胺）配合物相比，在tpaam配合物中观察到Ln—N（顶端）距离延长，对于较大的镧系元素而言这种延长比对于较小的镧系元素更为明显。对4f系列的tpaam配合物的溶液结构进行了分析，并与四齿配体tpa的镧系元素配合物的溶液结构进行了比较。质子核磁共振研究与两种配体均存在C(3)(v)对称溶液物种的情况一致。对于较大的镧系元素，与tpa配合物中占据的位置相比，阳离子远离顶端氮原子，而对于较小的镧系元素，两种配体的金属离子位于相似位置。非常令人惊讶的是，Eu(tpaam)Cl(3)配合物在298 K的D(2)O中的形成常数（log β(110) = 2.34(4)）与报道的Eu(tpa)Cl(3)的形成常数（298 K在D(2)O中log β(110) = 2.49(4)）非常相似，这表明与tpa的镧系元素配合物相比，向配体tpa中添加三个酰胺基团不会导致tpaam的镧系元素配合物稳定性增加。
