Symmetry driven self-assembly of metallo-supramolecular architectures

The self-assembly of well-defined metallosupramolecular aggregates highly depends on the symmetry of the ligands as well as of the metals. Approaches in which symmetry considerations allow the stepwise -'hierarchical'- assembly of helicate-type complexes from very simple catechol derivatives are described. In addition helicates and meso-helicates are stereoselectively obtained by the use of linear ligands possessing the relevant symmetry element for the formation of either diastereomer (even-odd principle). In case of helicates, this allows the preparation of enan-tiomerically pure complexes. Finally, the self-assembly of tetrahedral M4L4 complexes is described using either constrained flexible or highly predisposed rigid ligands. (author)