More Like this

1. Adsorption properties of acrolein, propanal, 2-propenol, and 1-propanol on Ag(111)

   https://doi.org/10.1039/D0CP04634E  

   Muir, Mark; Molina, David L.; Islam, Arephin; Abdel-Rahman, Mohammed K.; Trenary, Michael (November 2020, Physical Chemistry Chemical Physics)

   null (Ed.)

   Reflection absorption infrared spectroscopy and temperature programmed desorption were used to study the adsorption of acrolein, its partial hydrogenation products, propanal and 2-propenol, and its full hydrogenation product, 1-propanol on the Ag(111) surface. Each molecule adsorbs weakly to the surface and desorbs without reaction at temperatures below 220 K. For acrolein, the out-of plane bending modes are more intense than the CO stretch at all coverages, indicating that the molecular plane is mainly parallel to the surface. The two alcohols, 2-propenol and 1-propanol, have notably higher desorption temperatures than acrolein and display strong hydrogen bonding in the multilayers as revealed by a broadened and redshifted O–H stretch. For 1-propanol, annealing the surface to 180 K disrupts the hydrogen-bonding to produce unusally narrow peaks, including one at 1015 cm −1 with a full width at half maximum of 1.1 cm −1 . This suggests that 1-propanol forms a highly orderded monolayer and adsorbs as a single conformer. For 2-propenol, hydrogen bonding in the multilayer correlates with observation of the CC stretch at 1646 cm −1 , which is invisible for the monolayer. This suggests that for monolayer coverages, 2-propenol bonds with the CC bond parallel to the surface. Similarly, the CO stretch of propanal is very weak for low coverages but becomes the largest peak for the multilayer, indicating a change in orientation with coverage. 

   more » « less
2. Adsorption and reaction pathways of 7-octenoic acid on copper

   https://doi.org/10.1039/d1cp00167a  

   Bavisotto, Robert; Rana, Resham; Hopper, Nicholas; Olson, Dustin; Tysoe, Wilfred T. (March 2021, Physical Chemistry Chemical Physics)

   null (Ed.)

   The surface structure and reaction pathways of 7-octenoic acid are studied on a clean copper substrate in ultrahigh vacuum using a combination of reflection–absorption infrared spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption and scanning-tunneling microscopy, supplemented by first-principles density functional theory calculations. 7-Octenoic acid adsorbs molecularly on copper below ∼260 K in a flat-lying configuration at low coverages, becoming more upright as the coverage increases. It deprotonates following adsorption at ∼300 K to form an η 2 -7-octenoate species. This also lies flat at low coverages, but forms a more vertical self-assembled monolayer as the coverage increases. Heating causes the 7-octenoate species to start to tilt, which produces a small amount of carbon dioxide at ∼550 K and some hydrogen in a peak at ∼615 K ascribed to the reaction of these tilted species. The majority of the decarbonylation occurs at ∼650 K when CO 2 and hydrogen evolve simultaneously. Approximately half of the carbon is deposited on the surface as oligomeric species that undergo further dehydrogenation to evolve more hydrogen at ∼740 K. This leaves a carbonaceous layer on the surface, which contains hexagonal motifs connoting the onset of graphitization of the surface. 

   more » « less
3. On the formation of complex organic molecules in the interstellar medium: untangling the chemical complexity of carbon monoxide–hydrocarbon containing ice analogues exposed to ionizing radiation via a combined infrared and reflectron time-of-flight analysis

   https://doi.org/10.1039/C9CP01793C  

   Abplanalp, Matthew J.; Kaiser, Ralf I. (August 2019, Physical Chemistry Chemical Physics)

   Recently, over 200 molecules have been detected in the interstellar medium (ISM), with about one third being complex organic molecules (COMs), molecules containing six or more atoms. Over the last few decades, astrophysical laboratory experiments have shown that several COMs are formed via interaction of ionizing radiation within ices deposited on interstellar dust particles at 10 K (H 2 O, CH 3 OH, CO, CO 2 , CH 4 , NH 3 ). However, there is still a lack of understanding of the chemical complexity that is available through individual ice constituents. The present research investigates experimentally the synthesis of carbon, hydrogen, and oxygen bearing COMs from interstellar ice analogues containing carbon monoxide (CO) and methane (CH 4 ), ethane (C 2 H 6 ), ethylene (C 2 H 4 ), or acetylene (C 2 H 2 ) exposed to ionizing radiation. Utilizing online and in situ techniques, such as infrared spectroscopy and tunable photoionization reflectron time-of-flight mass spectrometry (PI-ReTOF-MS), specific isomers produced could be characterized. A total of 12 chemically different groups were detected corresponding to C 2 H n O ( n = 2, 4, 6), C 3 H n O ( n = 2, 4, 6, 8), C 4 H n O ( n = 4, 6, 8, 10), C 5 H n O ( n = 4, 6, 8, 10), C 6 H n O ( n = 4, 6, 8, 10, 12, 14), C 2 H n O 2 ( n = 2, 4), C 3 H n O 2 ( n = 4, 6, 8), C 4 H n O 2 ( n = 4, 6, 8, 10), C 5 H n O 2 ( n = 6, 8), C 6 H n O 2 ( n = 8, 10, 12), C 4 H n O 3 ( n = 4, 6, 8), and C 5 H n O 3 ( n = 6, 8). More than half of these isomer specifically identified molecules have been identified in the ISM, and the remaining COMs detected here can be utilized to guide future astronomical observations. Of these isomers, three groups – alcohols, aldehydes, and molecules containing two of these functional groups – displayed varying degrees of unsaturation. Also, the detection of 1-propanol, 2-propanol, 1-butanal, and 2-methyl-propanal has significant implications as the propyl and isopropyl moieties (C 3 H 7 ), which have already been detected in the ISM via propyl cyanide and isopropyl cyanide, could be detected in our laboratory studies. General reaction mechanisms for their formation are also proposed, with distinct follow-up studies being imperative to elucidate the complexity of COMs synthesized in these ices. 

   more » « less
4. Crystal structure of zymonic acid and a redetermination of its precursor, pyruvic acid

   https://doi.org/10.1107/S2056989019007072  

   Heger, Dominik; Eugene, Alexis J.; Parkin, Sean R.; Guzman, Marcelo I. (June 2019, Acta Crystallographica Section E Crystallographic Communications)

   The structure of zymonic acid (systematic name: 4-hydroxy-2-methyl-5-oxo-2,5-dihydrofuran-2-carboxylic acid), C 6 H 6 O 5 , which had previously eluded crystallographic determination, is presented here for the first time. It forms by intramolecular condensation of parapyruvic acid, which is the product of aldol condensation of pyruvic acid. A redetermination of the crystal structure of pyruvic acid (systematic name: 2-oxopropanoic acid), C 3 H 4 O 3 , at low temperature (90 K) and with increased precision, is also presented [for the previous structure, see: Harata et al. (1977). Acta Cryst. B 33 , 210–212]. In zymonic acid, the hydroxylactone ring is close to planar (r.m.s. deviation = 0.0108 Å) and the dihedral angle between the ring and the plane formed by the bonds of the methyl and carboxylic acid carbon atoms to the ring is 88.68 (7)°. The torsion angle of the carboxylic acid group relative to the ring is 12.04 (16)°. The pyruvic acid molecule is almost planar, having a dihedral angle between the carboxylic acid and methyl-ketone groups of 3.95 (6)°. Intermolecular interactions in both crystal structures are dominated by hydrogen bonding. The common R 2 2 (8) hydrogen-bonding motif links carboxylic acid groups on adjacent molecules in both structures. In zymonic acid, this results in dimers about a crystallographic twofold of space group C 2/ c , which forces the carboxylic acid group to be disordered exactly 50:50, which scrambles the carbonyl and hydroxyl groups and gives an apparent equalization of the C—O bond lengths [1.2568 (16) and 1.2602 (16) Å]. The other hydrogen bonds in zymonic acid (O—H...O and weak C—H...O), link molecules across a 2 1 -screw axis, and generate an R 2 2 (9) motif. These hydrogen-bonding interactions propagate to form extended pleated sheets in the ab plane. Stacking of these zigzag sheets along c involves only van der Waals contacts. In pyruvic acid, inversion-related molecules are linked into R 2 2 (8) dimers, with van der Waals interactions between dimers as the only other intermolecular contacts. 

   more » « less
5. Engineering thermoelectric and mechanical properties by nanoporosity in calcium cobaltate films from reactions of Ca(OH) ₂ /Co ₃ O ₄ multilayers

   https://doi.org/10.1039/D2NA00278G  

   Xin, Binbin; Ekström, Erik; Shih, Yueh-Ting; Huang, Liping; Lu, Jun; Elsukova, Anna; Zhang, Yun; Zhu, Wenkai; Borca-Tasciuc, Theodorian; Ramanath, Ganpati; et al (August 2022, Nanoscale Advances)

   Controlling nanoporosity to favorably alter multiple properties in layered crystalline inorganic thin films is a challenge. Here, we demonstrate that the thermoelectric and mechanical properties of Ca 3 Co 4 O 9 films can be engineered through nanoporosity control by annealing multiple Ca(OH) 2 /Co 3 O 4 reactant bilayers with characteristic bilayer thicknesses (b t ). Our results show that doubling b t , e.g. , from 12 to 26 nm, more than triples the average pore size from ∼120 nm to ∼400 nm and increases the pore fraction from 3% to 17.1%. The higher porosity film exhibits not only a 50% higher electrical conductivity of σ ∼ 90 S cm −1 and a high Seebeck coefficient of α ∼ 135 μV K −1 , but also a thermal conductivity as low as κ ∼ 0.87 W m −1 K −1 . The nanoporous Ca 3 Co 4 O 9 films exhibit greater mechanical compliance and resilience to bending than the bulk. These results indicate that annealing reactant multilayers with controlled thicknesses is an attractive way to engineer nanoporosity and realize mechanically flexible oxide-based thermoelectric materials. 

   more » « less