Structural Aspects of Helicates - Metallofoldamers: Supramolecular Architectures from Helicates to Biomimetics - page 136

28 31

29 32

30 33

34 35

Figure 4.16 Racemic ligands based on the Troger's base scaffold that give rise to racemic
mixtures of homochiral double-stranded helicates via diastereoselective self-recognition
processes.

36 37 38 39

Figure 4.17 Racemic ligands 36-39 based on binaphthyl scaffolds that give rise to racemic
mixtures of homochiral double- and triple-stranded helicates via diastereoselective self-
recognition process.

4.6 Diastereoselectivity I - “ Meso ”-Helicate versus Helicate Formation

As seen in the last chapter the octahedrally or tetrahedrally coordinated metal centres are
stereochemical elements. Thus, in a dinuclear assembly they can adopt either a L,L-, a
D,D-oraD,L-configuration. Whereas the first two would be a racemic mixture of heli-
cates if no further stereogenic element is present in the ligand structure, the last one is not
a real helicate corresponding to the definition given in the introduction but is rather a box-
like side by side complex which is called a “ meso ”-helicate [37]. Thus, meso -helicates