School of Engineering and Science - Jacobs University

Chapter 1
Introduction
The great majority of inorganic compounds are constructed of metallic atoms as principal
entities. Inorganic molecules have great potential because the number of elements
in purely inorganic molecules, combined with structural diversity, make them more powerful,
particularly as far as their application is concerned. In fact, the search for new
properties puts more importance on the elements in a framework than on the structure
itself. Polyoxometalates (POMs) are polynuclear metal oxygen clusters usually formed of
Mo, W or V that form a unique class of inorganic compounds because it is unmatched
in terms of structural versatility and properties [1–6]. They have potential applications
in many fields including medicine, catalysis, multifunctional materials, chemical analysis,
imaging, etc.
1.1 Historical perspectives
The polyoxometalates have been known since the work of Berzelius [7] on the ammonium
12-molybdophosphate in 1826, however, the study of polyoxoanion chemistry did not accelerate
until the discovery of the tungstosilicic acids and their salts by Marignac [8] in
1862, when analytical compositions of such heteropoly acids were precisely determined.
Thereafter, the field developed rapidly, so that over 60 different types of heteropoly acids
(giving rise to several hundred salts) had been described by the first decade of this century.
Pauling [9] proposed a structure for 12:1 complexes based on an arrangement of twelve
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