Resolution and Kinetic Stability of a Chiral Supramolecular Assembly Made of Labile Components.

The importance of chirality for recognition processes in nature is impressively exemplified by the different tastes of (R)and (S)-asparagine,[1] and the vastly different pharmacological effects of the two enantiomers of thalidomide.[2] Chirality is not the exclusive domain of organic chemistry, many metals can also serve as centers of chirality.[3] The most frequent case is an octahedral arrangment of three bidentate ligands around a metal center to form D or L absolute configurations. Chirality at metal centers has been found to play an important role in nature, for example, for the siderophore-mediated iron uptake in many organisms.[4] D/L Isomerization of tris-bidentate complexes of the labile high-spin ferric ion or its closely related gallium(iii) analogues is rapid in aqueous solution. Tris(catecholate)gallium(iii) complexes, model compounds of iron siderophores, usually racemize fast. Racemization rates of 10(1) sÿ1 for a mononuclear complex[5] and 0.10(1) sÿ1 for a dinuclear helix[6] were determined by NMR studies. The isomerization was found to

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