| Abstract
| - The Pr(III), Nd(III), Eu(III), Tb(III), Dy(III), and Yb(III) complexes of the chiral enantiopure hexaazamacrocycle L have been synthesized and characterized by 2D NMR, CD, and ESI MS, as well as by crystallographic methods. The [YbL]3+ complex exists in two stable diastereomeric forms, which differ in the direction of the helical twist of the macrocyclic ligand. Both forms of the Yb(III) complex have been isolated, and their interconversion was studied in various solvents.
- 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. The2D NMR spectra confirm the identity of these complexes and indicate C2 symmetry of the [LnL]3+ and Cs symmetryof the [LnL1]3+ complexes. The crystal structures of the [PrL(NO3)(H2O)2](NO3)2, [EuL(NO3)(H2O)2](NO3)2, [DyL(NO3)2]2[Dy(NO3)5]·5CH3CN, [YbL(NO3)2]2[Yb(NO3)5]·5CH3CN, [YbL(H2O)2](NO3)3·H2O, and [EuL1(NO3)(H2O)2]0.52[EuL1(NO3)2]0.48(NO3)1.52·0.48H2O 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 ofcomplex, the conformation of the macrocycle and the axial ligation are different. The crystallographic, NMR, andCD data show that the [YbL]3+ complex exists in two stable forms. Both forms of the Yb(III) complex have beenisolated, and their interconversion was studied in various solvents. The two forms of [YbL]3+ complex correspondto two diastereomers of ligand L, which differ in the sense of the helical twist and the configuration at the stereogenicamine nitrogen atoms. In one of the stereoisomers, the macrocycle L of (RRRR) configuration at the stereogeniccyclohexane carbon atoms adopts the (RSRS) configuration at the amine nitrogen atoms, while in the otherstereoisomer, 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, thusrepresenting the rare case of helicity inversion controlled by the solvent.
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