Achirality molecular links

Niwano H, Nakata M, Thisayukta J, Link DR, Takezoe H, Watanahe J (2004) Chiral memory on transition between the B2 and B4 phases in achiral banana-shaped molecular system. J Phys Chem B 108 14889-14896... 

In the aforementioned work, ligands are attached covalently to a polymer. An interesting non-covalent attachment was reported early on by Wilson and Whitesides [15]. An achiral phosphine ligand linked to a biotin unit (Structure 6) interacted specifically with the protein avidin in aqueous solution to impose stereoselectivity in catalytic hydrogenation. In the rhodium-catalyzed hydrogenation of a-acetamidoacrylic acid in buffered aqueous solution, ee values of up to 40% were observed at TONs of 500 in a 48 h mn. Catalyst recovery was not a motivation for this work, but during workup the catalyst was separated from the low molecular weight products by ultrafiltration. 

In the first part of this chapter, we will present chiral supramolecular architectures formed from achiral building units that are linked via metal-ligand coordination, where chirality of the assembly results only from the asymmetric arrangement of the molecular components. In the second section, we will deal with chiral assemblies that result from resolved chiral bridging ligands, where chiral information can be transferred to the metal centre and hence a predetermination of the absolute configuration at the metal centre can be achieved and, eventually, the control of the chirality of the supramolecular architecture which can also be defined as stereoselective asymmetric supramolecular assembly . 

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