Gregoliński Janusz, Lis Tadeusz, Cyganik Marta, Lisowski Jerzy
Department of Chemistry, University of Wrocław, 14 F. Joliot-Curie, 50-383 Wrocław, Poland.
Inorg Chem. 2008 Dec 15;47(24):11527-34. doi: 10.1021/ic8005986.
The La(III), Ce(III), Pr(III), Nd(III), Sm(III), and Eu(III) complexes of the racemic heterochiral nonaaza macrocyclic amine L have been synthesized and characterized by spectroscopic methods. The X-ray crystal structures of the [PrL][Pr(NO(3))(6)].CH(3)OH and the isomorphic [NdL][Nd(NO(3))(6)].CH(3)OH complexes show that all nine nitrogen atoms of the macrocycle coordinate to the Ln(3+) ion, completing its coordination sphere. The macrocycle wraps tightly around the metal ion in double-helical fashion. The structures reveal the RRRRSS/SSSSRR configuration at the stereogenic carbon atoms of the three cyclohexane rings, confirming the heterochiral nature of the parent 3 + 3 macrocycle obtained in the condensation of racemic trans-1,2-diaminocyclohexane and 2,6-diformylpyridine. The NMR spectra of the isolated complexes indicate the presence of low C(1) symmetry LnL complexes. The same symmetry is indicated by the X-ray crystal structures of Pr(III) and Nd(III) complexes, which show that for the RRRRSS enantiomer of the macrocycle L, the helix axis passes through the cyclohexane ring of RR chirality and the opposite pyridine ring. The NMR studies of complex formation in solution by the paramagnetic Pr(3+) and Eu(3+) ions indicate that the initially formed LnL complexes are of C(2) symmetry. For the RRRRSS enantiomer of the macrocycle L in the C(2)-symmetric species, the helix axis passes through the cyclohexane ring of SS chirality and the opposite pyridine ring. The C(1)-symmetric and C(2)-symmetric forms of the LnL complexes constitute a new kind of isomers and the conversion of the kinetic complexation product of C(2) symmetry into the thermodynamic product of C(1) symmetry corresponds to an unprecedented switching of the orientation of the helix axis within the macrocycle framework.
已合成外消旋杂手性九氮杂大环胺L的镧（III）、铈（III）、镨（III）、钕（III）、钐（III）和铕（III）配合物，并通过光谱方法对其进行了表征。[PrL][Pr(NO₃)₆]·CH₃OH和同构的[NdL][Nd(NO₃)₆]·CH₃OH配合物的X射线晶体结构表明，大环的所有九个氮原子均与Ln(3+)离子配位，形成其配位球。大环以双螺旋方式紧密包裹在金属离子周围。这些结构揭示了三个环己烷环的手性碳原子处的RRRRSS/SSSSRR构型，证实了在外消旋反式-1,2-二氨基环己烷与2,6-二甲基吡啶缩合反应中得到的母体3 + 3大环的杂手性性质。分离得到的配合物的核磁共振谱表明存在低C₁对称性的LnL配合物。Pr(III)和Nd(III)配合物的X射线晶体结构也表明了相同的对称性，这表明对于大环L的RRRRSS对映体，螺旋轴穿过RR手性的环己烷环和相对的吡啶环。顺磁性的Pr(3+)和Eu(3+)离子在溶液中形成配合物的核磁共振研究表明，最初形成的LnL配合物具有C₂对称性。对于C₂对称物种中大环L的RRRRSS对映体，螺旋轴穿过SS手性的环己烷环和相对的吡啶环。LnL配合物的C₁对称和C₂对称形式构成了一种新型异构体，C₂对称性的动力学络合产物向C₁对称性的热力学产物的转化对应于大环框架内螺旋轴取向前所未有的切换。
