PHYSICAL METHODS IN STUDYING POLYOXOMETALATES: EXTENDED HUECKEL MOLECULAR ORBITAL CALCULATIONS AND SPECTROSCOPIC PROPERTIES

摘要

Polyoxometalates (POMs) of vanadium, molybdenum and tungsten and to some extent, niobium and tantalum are very important and interesting classes of con-piexes with great potential in many applications. Since in many cases their structures prove to be unchanged in solution, many methods are applicable for studying their molecular and electronic structures. These studies are expected to be useful for understanding their role in many processes and for rational design of new compounds that are promising for applications. Certainly, molecular structure may be revealed from X-ray diffraction experi-ments on a single crystal. Sometimes a general idea about the atomic dispositions may be obtained from large-angle X-ray scattering on POM in aqueous solution. Localization of protons may be detected by means of the neutron diffraction on large crystals. Nevertheless, many of the details of the structure, especially the peculiarities of the electronic structure can be investigated by the use of the physical methods.