Self-sorting Subcomponent Rearrangement During Crystallization

Hutin, M.; Cramer, C. J.; Gagliardi, L.; Rehaman, A.; Bernardinelli, G.; Cerny, R.; Nitschke, J. R.
J. Am. Chem. Soc. 2007, 129, 8774.

The incorporation of enantiopure 1-amino-2,3-propanediol amine subcomponent into a dicopper double helicate resulted in perfect chiral induction of the helicate's twist. DFT calculations allowed the determination of the helicity of the complex in solution. The same helical induction, in which S-amines induced a Λ helical twist, was observed in the solid state by X-Ray crystallography. Electronic structure calculations also revealed that the unusual deep green color of this class of complex was due to a metal-to-ligand charge transfer excitation, in which the excited state possesses a valence delocalized Cu₂³⁺ core. The use of a racemic amine subcomponent resulted in the formation of a dynamic library of 6 diastereomeric pairs of enantiomers. This library self-sorted during crystallization, as the mixture converted into a single pairs of enantiomers via covalent and coordinative rearrangements. We were able to observe this process reverse upon redissolution, as initial coordinative ligand exchange was followed by covalent imine metathesis.

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