From simple linkable building blocks to structures with increasing size and complexity

Polyoxometalates provide excellent models for the understanding of basic as pects of molecular growth processes: Using the same reaction, i.e., the aci dification of the aqueous solution of oxoanions, the resulting products spa n three important areas of matter, from the micro-, through the meso- to th e macro"cosmos", the latter of which is characterized by crystallinity or r espectively, translational invariance. Upon different types of linking of w ell-defined building units an overwhelming variety of different species can be formed. Novel types of molecular growth processes (including those base d on a type of induced cascade) are described leading to different ring-sha ped, electron-rich, mixed-valence, giant polyoxomolybdates with nano-sized cavities. The recent synthesis of various large ring-duster systems has, fu rthermore, opened new perspectives for a novel supramolecular chemistry in nano-scale dimensions.