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Spectroscopic Characterization of Ru-based Catalysts for Artificial PhotosynthesisSpeaker: Dooshaye Moonshiram, Purdue University
401/A1100 @ 2:00 PM
EPR, Raman and XAS characterization of the electronic structure and molecular geometry of peroxo intermediates in blue dimer as well as single-site water-oxidizing complexes are reported. Formation of metal bound peroxides as the result of O-O coupling has been implicated in the mechanism of catalytic water oxidation by Photosystem II oxygen evolving complex (OEC) and in Ru-based catalysts(3). However, such intermediates were never isolated and their structural and electronic characterization has not been reported. The intermediates described here are direct products of the O-O bond formation step in the studied catalysts. The combination of all these techniques enabled identification of the critical requirements for catalytic water oxidation for the design of new economical and efficient catalysts.
1. Esper B, Badura A, & Rogner M (2006) Photosynthesis as a power supply for (bio) hydrogen production. Trends in Plant Science 11.
2. Moonshiram D, et al. (2012) Structure and Electronic Configurations of the Intermediates of Water Oxidation in Blue Ruthenium Dimer Catalysis. J.Am.Chem.Soc. 134(10):4625-4636.
3. Concepcion JJ, Jurss JW, Templeton JL, & Meyer TJ (2008) One Site is Enough. Catalytic Water Oxidation by [Ru(tpy)(bpm)(OH2)]2+ and [Ru(tpy)(bpz)(OH2)]2+. J Am Chem Soc 130(49):16462-16463.
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Utilizing Powder X-ray Diffraction to Understand Unknown Structural Motifs and Phase TransitionsSpeaker: Dr. Saul Lapidus, Material Science Division, Argonne National Laboratory
401/A5000 @ 9:30 AM
Cs2MnII[MnII(CN)6] has the archetypal Prussian blue structure with cations in the cubic voids. Substitution with smaller alkali ions lead to structural distortions and a marked increase in ordering temperatures with increasing distortions. On the other hand, substitution of larger cations, NMe4+ and NEt4+ drive a rearrangement of the Mn-CN-Mn network and produce several previously unobserved Mn(II) coordination geometries and very different structural motifs.
Zn(CN)2 forms an interpenetrated diamondoid structure and undergoes a number of transitions upon the elevation of pressure. The structures of the four new crystalline phases have been resolved through ab-initio structural determination by synchrotron powder diffraction. The specific transition depends on the hydrostatic fluid used, and surprisingly three of these new phases involve a close to 2-fold expansion of volume. This counter-intuitive expansion is due to minimization of the solid and fluid volume, rather than just the solid volume.
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In situ Powder Diffraction for Industrial Gas SeparationsSpeaker: Dr. Matthew R. Hudson, NIST Center for Neutron Research
401/A1100 @ 10:00 AM
 Hudson, M.R.; Queen, W.L.; Mason, J.A.; Fickel, D.W.; Lobo, R.F.; Brown, C.M.; JACS, 2012, 134, 1970.
 Geier, S. J.; Mason, J. A.; Bloch, E.D.; Queen, W. L.; Hudson, M. R.; Brown, C. M.; Long, J. R. Chem. Sci. 2013, 4, 2054.
 Queen, W. L.; Brown, C. M.; Britt, D. K.; Zajdel, P.; Hudson, M. R.; Yaghi, O. M.; J. Phys. Chem. C, 2011, 115, 24915.
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402/AUD @ 3:00 PM
ACA 2013APS Conference