From simple building blocks to structures with increasing size and complexity

• Published in: Coordination chemistry reviews 1999-02, Vol.182 (1), p.3-17
• Main Authors: Müller, A., Kögerler, P.
• Format: Article
• Language: English
• Subjects: Clusters; Polyoxometalates; Supramolecular chemistry
• ISSN: 0010-8545; 1873-3840
• DOI: 10.1016/S0010-8545(98)00226-4

In Nature, complex molecular systems like proteins have evolved (natura naturans) which are perfectly suited to their functions. These are produced in a sequence of steps under dissipative conditions—that is, far from equilibrium. The challenge for the chemist is to synthesize correspondingly complex multi-functional molecules also under non-equilibrium (non-dissipative) conditions using multi-component, one-pot reactions, without having to separate and purify each single intermediate product. Relevant model reactions have been discovered in solutions of simple oxoanions of the early transition metals: novel types of molecular growth processes with feedback (including a type of induced cascade) are described leading to different ring-shaped, electron-rich, mixed-valence, giant polyoxomolybdates with nanosized cavities. These can—due to the generation of defects—be covalently linked together to form chains as well as layered mesoporous compounds with properties relevant for materials science. They can also start growing again. The largest polyoxometalate cluster obtained on the basis of this growth process to-date has 248 Mo atoms. Remarkably, such giant ring species can also act as hosts for other clusters forming new types of supramolecular compounds.