LAST UPDATE 2006.03.08

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AN OVERVIEW OF OUR RESEARCH

We are working with 'Polyoxometalate (POM) Chemistry', and our main targets are 'Peroxopolyoxometalates (PPOMs)', which are polyoxometalates having peroxo groups. Our aim is to elucidate basic chemistry (formation, synthesis, structure and physical property) of PPOMs, to clarify the relationship between structural feature of PPOMs and coexisting cations/molecules in order to design novel anion or crystal structures, and to develop possible way for applications of PPOMs. There are a number of laboratories in the world working with POM chemistry, either basic chemistry or application. However, very few laboratories deal with PPOMs, and our lab is one of them. Even in the past there were very few reports on PPOMs. The only systematic research has been made by Rolf Stomberg, Chalmers Tekniska Högskola in Göteborg, on mainly peroxoisopolymolybdates. Other important works were made by W. P. Griffith at Imperial College, London. In the middle of 1980's a peculiar phosphooctaperoxotetrametalates (so-called Venturello-type compounds) and their derivatives were paid attention as oxidation catalysts (in other expression, oxygen carriers). Such a situation makes PPOM chemistry quite underdeveloped. Besides, complicated formation reactions, instability of peroxide/peroxo groups in both liquid and solid phases, which makes control of peroxide contents (and thus pH value) of the solution almost impossible in especially tungstate and vanadate (acidic region) cases, and poor quality of crystals have prevented the progress of PPOM research. We believe, however, a lot of phenomena and compounds are veiled in PPOM chemistry, and try to seek them. Please refer 'THESIS'', 'PRESENTATION' and MEMBERS' on what we are working with.

You can find structures of novel PPOMs we have found and some discussions on these compounds in 'NEW COMPLEXES' (temporary unavailable). A peculiar structural feature of a PPOM is introduction of 7-coordinated pentagonal bipyramidal decahedra, which often gives unique structures to aggregates formed. An addenda atom usually bears one or two peroxo group(s) on it in the form of h2-coordination. In each case peroxo group(s) lie on the equatorial plane resulting in pentagonal geometry of the equatorial plane. Some interesting features of PPOMs we have found are: # Isomerization of polyanions by different connection of coordination polyhedra, and positions of peroxides # Dimeric (mainly molybdates) and trimeric (mainly tungstates) building unit # Polymeric PPOMs having peroxo groups as bridging ligands # Clathrate type crystal structures with polyanions as a part of host and organic cations as guests # Construction of polyanions with alkaline metal cations as templates # Face sharing between different types of coordination polyhedra

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