M40 is a four-fold symmetry macrocyclic ligand endowed with axial and central chiral elements, all of R configuration. It promptly binds late lanthanides (Yb III and Lu III) yielding a negative helicity, as witnessed by NIR-electronic circular dichroism. In the course of a few hours, a new conformation of the complex takes over, which has opposite helicity and allows for a dynamic free-bound equilibrium. Upon slow solvent evaporation, the original conformation is retrieved and the whole dynamic process can be started again, as in a sandclock, allowing one to envisage applications as a time-marker chiral switch. Helices are a-changing: In a macrocyclic complex of late lanthanides, a slow ligand conformational rearrangement in solution leads to helicity inversion that can be reverted by slow solvent evaporation and provides a circular dichroism time-marker (see graphic).
REVERSIBLE MUTAROTATION IN A MACROCYCLIC YTTERBIUM COMPLEX
DI BARI, LORENZO
2011-01-01
Abstract
M40 is a four-fold symmetry macrocyclic ligand endowed with axial and central chiral elements, all of R configuration. It promptly binds late lanthanides (Yb III and Lu III) yielding a negative helicity, as witnessed by NIR-electronic circular dichroism. In the course of a few hours, a new conformation of the complex takes over, which has opposite helicity and allows for a dynamic free-bound equilibrium. Upon slow solvent evaporation, the original conformation is retrieved and the whole dynamic process can be started again, as in a sandclock, allowing one to envisage applications as a time-marker chiral switch. Helices are a-changing: In a macrocyclic complex of late lanthanides, a slow ligand conformational rearrangement in solution leads to helicity inversion that can be reverted by slow solvent evaporation and provides a circular dichroism time-marker (see graphic).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
