Synthesis and characterization of Lanthanide Aluminotungstates and Rhenium Polyoxometalates: Potential Application in Molecular Information Storage Devices

Polyoxometalates (abbreviated as POMs) are metal-oxide clusters with frameworks built from group 5 or 6 transition metals linked by shared oxide ions. The Keggin structure is one of the most famous structural forms of POMs. Keggin anions have a general formula of [XM12O40 ]n-, where X is a p-block atom and M is a transition metal atom such as W or Mo. Upon removal of one MO4+ unit from the Keggin anion, the monovacant structure [XM11O39] n- is formed. Those POMs that have lost one or more metal center are called lacunary POMs, which are very nice building blocks for the fabrication of coordination polymers. My research focuses on two facets of POM chemistry: 1) Lanthanide chemistry of aluminum tungstate monovacant Keggin and 2) Rhenium chemistry of aluminum tungstate Keggin and Wells-Dawson POM alpha1 -P2W17O61.;In lanthanide POM research area, we obtained the following results:;1) The starting material aluminum tungstate monovacant Keggin &agr;-K 9AlW12O39 was synthesized. Its single crystal was firstly identified by multinuclear NMR and X-ray crystallography. Its redox properties on the nano-scale solid state were determined by Conducting Electrostatic Force Mode (EFM) probes. It is well known that for POMs, a number of varies redox states are normally stable and reversible. Thus we estimated that POMs can potentially be used in molecular information storage applications, which we refer to as "redox disk drives".;2) Eight lanthanide aluminum tungstate Keggin complexes were synthesized. In their molecular structures (identified by multinuclear NMR and X-ray crystallography), each &agr;-AlW11O39 is connected by lanthanide (III) cations to form 1D and 2D networks. All AlW11O39 Keggin POMs are regularly aligning on a flat plane. Microscopic data also verified that there is layer-by-layer morphology in this series of compounds.;Overall, we postulate that aluminum tungstate Keggin POMs are a very promising materials for making future information storage device because they have several stable redox states and can be reduced by adding voltage in solid state, The Keggin POMs can be regularly aligned on a flat plane,;3) In rhenium chemistry research area, we successfully synthesized rhenium complexes of the [alpha1-P2W17O 61]10- and &agr;-K9AlW13O 39. The structure info of [ReVO(alpha1-P2W 17O61)]7- was identified by multinuclear NMR and X-ray crystallography. The cyclic-voltammetry of [ReVO(alpha1-P 2W17O61)]7- has also been measured and compared to the [ReVO(alpha2-P 2W17O61)]7- isomer. A rhenium derivative of &agr;-K9AlW11O39 also has been synthesized. Multinuclear NMR gives structure information. After oxidation in air, this compound can aggregate to form insoluble nanoparticles.