Gregoliński Janusz, Slepokura Katarzyna, Lisowski Jerzy
Department of Chemistry, University of Wrocław, 14 F. Joliot-Curie, 50-383 Wrocław, Poland.
Inorg Chem. 2007 Sep 17;46(19):7923-34. doi: 10.1021/ic700831z. Epub 2007 Aug 17.
Lanthanide(III) complexes of the enantiopure chiral hexaaza tetraamine macrocycle L, 2(R),7(R),18(R),23(R)-1,8,15,17,24,31-hexaazatricyclo[25.3.1.1.0.0]-dotriaconta-10,12,14,26,28,30-hexaene, as well as of its meso-type 2(R),7(R),18(S),23(S)-isomeric macrocycle L1, have been synthesized and characterized by spectroscopic methods. The 2D NMR spectra confirm the identity of these complexes and indicate C2 symmetry of the [LnL]3+ and Cs symmetry of the [LnL1]3+ complexes. The crystal structures of the PrL(NO3)(H2O)22, EuL(NO3)(H2O)22, [DyL(NO3)2]2[Dy(NO3)5] x 5CH3CN, [YbL(NO3)2]2[Yb(NO3)5] x 5CH3CN, YbL(H2O)23 x H2O, and [EuL1(NO3)(H2O)2]0.52[EuL1(NO3)2]0.48(NO3)1.52 x 0.48H2O complexes have been determined by single-crystal X-ray diffraction. In all complexes, the lanthanide(III) ions are coordinated by six nitrogen atoms of the macrocycle L or L1, but for each type of complex, the conformation of the macrocycle and the axial ligation are different. The crystallographic, NMR, and CD data show that the [YbL]3+ complex exists in two stable forms. Both forms of the Yb(III) complex have been isolated, and their interconversion was studied in various solvents. The two forms of [YbL]3+ complex correspond to two diastereomers of ligand L, which differ in the sense of the helical twist and the configuration at the stereogenic amine nitrogen atoms. In one of the stereoisomers, the macrocycle L of (RRRR) configuration at the stereogenic cyclohexane carbon atoms adopts the (RSRS) configuration at the amine nitrogen atoms, while in the other stereoisomer, the macrocycle L of (RRRR) configuration at the stereogenic cyclohexane carbon atoms adopts the (SSSS) configuration at the amine nitrogen atoms. The (RRRR)(RSRS) isomer is quantitatively converting to the (RRRR)(SSSS) isomer in water solution, while the reverse process is observed for an acetonitrile solution, thus representing the rare case of helicity inversion controlled by the solvent.
对映体纯的手性六氮杂四胺大环L（2(R),7(R),18(R),23(R)-1,8,15,17,24,31-六氮杂三环[25.3.1.1.0.0]-三十六-10,12,14,26,28,30-六烯）及其内消旋型2(R),7(R),18(S),23(S)-异构体大环L1的镧系(III)配合物已通过光谱方法合成并表征。二维核磁共振谱证实了这些配合物的结构，并表明[LnL]3+配合物具有C2对称性，[LnL1]3+配合物具有Cs对称性。通过单晶X射线衍射确定了PrL(NO3)(H2O)22、EuL(NO3)(H2O)22、[DyL(NO3)2]2[Dy(NO3)5]·5CH3CN、[YbL(NO3)2]2[Yb(NO3)5]·5CH3CN、YbL(H2O)23·H2O和[EuL1(NO3)(H2O)2]0.52[EuL1(NO3)2]0.48(NO3)1.52·0.48H2O配合物的晶体结构。在所有配合物中，镧系(III)离子均由大环L或L1的六个氮原子配位，但对于每种类型的配合物，大环的构象和轴向配位情况均不同。晶体学、核磁共振和圆二色光谱数据表明，[YbL]3+配合物以两种稳定形式存在。Yb(III)配合物的两种形式均已分离，并在各种溶剂中研究了它们的相互转化。[YbL]3+配合物的两种形式对应于配体L的两种非对映异构体，它们在螺旋扭曲方向和手性胺氮原子处的构型不同。在其中一种立体异构体中，在手性环己烷碳原子处具有(RRRR)构型的大环L在胺氮原子处采用(RSRS)构型，而在另一种立体异构体中，在手性环己烷碳原子处具有(RRRR)构型的大环L在胺氮原子处采用(SSSS)构型。(RRRR)(RSRS)异构体在水溶液中定量转化为(RRRR)(SSSS)异构体，而在乙腈溶液中观察到相反的过程，因此代表了由溶剂控制螺旋反转的罕见情况。
