Planarity of para Hexaphenyl

URL:http://link.aps.org/doi/10.1103/PhysRevLett.82.3625 DOI:10.1103/PhysRevLett.82.3625We present experimental and theoretical findings on the geometry of polycrystalline para hexaphenyl via Raman scattering. The planarity of the molecule is affected by hydrostatic pressure and temperature. Our studies indicate that the potential energy curve which governs the torsional motion between neighboring phenyl rings is “W” shaped. We determine the activation energy to promote the molecule from a nonplanar to a planar state to be 0.04 eV, in good agreement with our quantum chemical calculations. From the relative intensities of the 1280cm-1 to the 1220cm-1 Raman modes we show that high pressure planarizes the molecules, modifying the “W”-shaped potential energy curve to a “U”-shaped one.We acknowledge the financial support from U.S. Army Grant No. DAAL03-92-0381, University of Missouri Research Board and Österreichische Nationalbank (Project No. 6608)

Advanced Biomimetic Materials for Reversible CO2 Capture from Air [abstract]

Only abstract of poster available.Track I: Power GenerationThe world is rightly focused on climate change. The U.N. Intergovernmental Panel on Climate Change(IPCC) identified carbon capture and storage (CSS) as a critical technology for reducing emissions, not only from power plants but also from industries that manufacture cement, chemicals and steel. The capture of CO2 from air and its long-term storage also presents the method of last resort to combat excessive atmospheric CO2 concentrations. IPPC concluded that the world has to reverse the increase of greenhouse gas emissions by 2020 to avert disastrous environment consequences. Modern societies largely rely on the fossil fuels to generate energy (electricity, heat, etc.) and as fuels for transportation, and the principle mode of fossil fuel use involves its direct combustion to water and carbon dioxide. Efforts to reduce CO2 emissions are directed at improving the combustion efficiency and/or at the development of technologies for carbon capture and storage (CCS). The fuel combustion efficiency depends on the type of fuel (coal, gaseous or liquid hydrocarbons, H2), the oxidizing agent (air, O2-enriched air, stream), and combustion conditions (pres., temp., cat.). It is the primary aim of CCS technologies to capture CO2 at the source and its long-term storage. The 2007 MIT study “The Future of Coal” concluded that “CCS is the critical enabling technology that would reduce CO2 emissions significantly while also allowing coal to meet the world's pressing energy needs.” The three major approaches to CCS involve post-combustion scrubbing, oxyfuel, and pre-combustion decarbonization technologies. It is the goal of our research to develop advanced materials for CO2 scrubbing. Nature has evolved five pathways for autotrophic CO2 fixation and our approach is inspired by the mechanism of the photosynthetic carbon assimilation via the Calvin-Bassham-Benson cycle. The mechanism of the Rubisco-catalysis involves the activation by way of carbamylation of active-site Lys by an activator CO2 (ACO2), and the carbamate thus formed is stabilized by complexation to Mg2+ and by NH...OC hydrogen-bonding. We present results of theoretical and mechanistic studies of organic materials that mimic Rubisco's capacity for reversible CO2 capture and discuss the fixation of these materials on porous, solid supports to achieve large-scale CO2 scrubbing from ambient air