Metal-oxo clusters, including peroxoniobophosphate clusters, hafnium sulfate clusters, and zirconium sulfate clusters are promising precursors for metal oxide thin films, as well as patterning with light, exploiting the radiation sensitive peroxide ligands. Discrete nanometer-size clusters control the nanometer-size features that we can pattern. Moreover, the peroxide ligand for both the group V (Nb) and group IV (Zr, Hf) clusters allows pH stability across broad pH ranges, which we have dubbed amphoteric clusters. Two peroxoniobophosphate clusters have been isolated as tetramethylammonium salts having the stoichiometries: TMA5[HNb4P2O14(O2)4]●9H2O and TMA3[H7Nb6P4O24(O2)6]●7H2O. The two related clusters are interconvertible by choice of solution conditions. Acid stability of these clusters allows us to explore incorporation of transition metals including Cr, Mn, Fe, Co, Ni, or Cu into these clusters, which is the focus of current study. Success in these efforts will open up the opportunity for applications such as new energy selective ion electrodes or new films with redox active properties. Synthesis of targeted heterometallic clusters also opens up a more thorough understanding of Nb speciation in acid. Solution speciation of hafnium and zirconium has been explored extensively at acidic pH, but relatively little information is known about the behavior of these metals at alkaline pH. Several acidic and sulfate-containing hafnium-oxo clusters have been isolated, as well as the zirconium analogs; however, only one alkaline hafnium cluster has been reported at this time. Due to the similar chemistry of hafnium and zirconium, synthesis of an alkaline zirconium analog should be possible, but proves challenging. In addition to synthesis of new clusters, further determination of speciation at high pH is a current focus of study.

Solution speciation of amphoteric early transition metal clusters

253rd National Meeting (2017)

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