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1. Plausible Proton Transfer Data Files

   https://doi.org/10.6084/m9.figshare.30875087  

   Van_Vranken, David (January 2025, figshare)

   A zipped file containing:51M_Heteroatom.csv - 51M proton transfer steps from heteroatom acids to heteroatom bases, with SMIRKS, calculated log k1, and pKas,5KCarbonPT.csv - 5K proton transfer steps from carbon acids to heteroatom bases, with SMIRKS, calculated log k1, and pKas, Brønsted β values, statistical factors (qB, pB, qC, pC) intrinsic rate constants (ko),49ExperimentalCarbonPT.csv - 49 proton transfers from heteroatom acids to carbon bases in SMIRKS format, with experimentally measured log k1, and literature references.51M_heteroatom_raw – a subfolder with two files containing lists of 7.6K heteroatomic acids and bases in SMILES format with the acidic and basic atoms labeled, with pKas, literature references: Acid.csv, ConBase.csv100_Heteroatom.csv - A representative sample set of 100 out of the 51M proton transfer steps100K_Heteroatom.csv - A representative sample set of 100,000 out of the 51M proton transfer stepscarbon_acid_raw – a subfolder containing a list of intrinsic rate constants for carbon acids in SMILES format, with statistical factors (Carbon_Acids.csv) and a subfolder named Bases containing seven lists of heteroatom base classes (ArO-.csv, R2NH.csv, R3N.csv, “RCO2- and ArCO2-.csv”, RNH2.csv, RO-.csv and RS-.csv). Lists of heteroatom bases are in SMILES format, sectioned by class and with statistical factors, selected from the Heteroatom set 

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2. NMR Study of CO ₂ Capture by Butylamine and Oligopeptide KDDE in Aqueous Solution: Capture Efficiency and Gibbs Free Energy of the Capture Reaction as a Function of pH**

   https://doi.org/10.1002/cphc.202300053  

   Yang, Kaidi; Schell, Joseph; Gallazzi, Fabio; Wycoff, Wei; Glaser, Rainer (June 2023, ChemPhysChem)

   Abstract We have been interested in the development of rubisco‐based biomimetic systems for reversible CO₂ capture from air. Our design of the chemical CO₂ capture and release (CCR) system is informed by the understanding of the binding of the activator CO₂(^ACO₂) in rubisco (ribulose‐1,5‐bisphosphate carboxylase/oxygenase). The active site consists of the tetrapeptide sequence Lys‐Asp‐Asp‐Glu (or KDDE) and the Lys sidechain amine is responsible for the CO₂ capture reaction. We are studying the structural chemistry and the thermodynamics of CO₂ capture based on the tetrapeptide CH₃CO−KDDE−NH₂ (“KDDE”) in aqueous solution to develop rubisco mimetic CCR systems. Here, we report the results of ¹H NMR and ¹³C NMR analyses of CO₂ capture by butylamine and by KDDE. The carbamylation of butylamine was studied to develop the NMR method and with the protocol established, we were able to quantify the oligopeptide carbamylation at much lower concentration. We performed a pH profile in the multi-equilibrium system and measured amine species and carbamic acid/carbamate species by the integration of ¹H NMR signals as a function of pH in the range 8 ≤ pH ≤ 11. The determination of ΔG₁(R) for the reaction R−NH₂ + CO₂ R−NH−COOH requires the solution of a multi‐equilibrium equation system, which accounts for the dissociation constants K₂ and K₃ controlling carbonate and bicarbonate concentrations, the acid dissociation constant K₄ of the conjugated acid of the amine, and the acid dissociation constant K₅ of the alkylcarbamic acid. We show how the multi‐equilibrium equation system can be solved with the measurements of the daughter/parent ratio X, the knowledge of the pH values, and the initial concentrations [HCO₃⁻]₀ and [R‐NH₂]₀. For the reaction energies of the carbamylations of butylamine and KDDE, our best values are ΔG₁(Bu) = −1.57 kcal/mol and ΔG₁(KDDE) = −1.17 kcal/mol. Both CO₂capture reactions are modestly exergonic and thereby ensure reversibility in an energy‐efficient manner. These results validate the hypothesis that KDDE‐type oligopeptides may serve as reversible CCR systems in aqueous solution and guide designs for their improvement. 

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3. Aqueous reactions of organic triplet excited states with atmospheric alkenes

   https://doi.org/10.5194/acp-19-5021-2019  

   Kaur, Richie; Hudson, Brandi M.; Draper, Joseph; Tantillo, Dean J.; Anastasio, Cort (January 2019, Atmospheric Chemistry and Physics)

   Abstract. Triplet excited states of organic matter are formed when colored organicmatter (i.e., brown carbon) absorbs light. While these “triplets” can beimportant photooxidants in atmospheric drops and particles (e.g., theyrapidly oxidize phenols), very little is known about their reactivity towardmany classes of organic compounds in the atmosphere. Here we measure thebimolecular rate constants of the triplet excited state of benzophenone(³BP^∗), a model species, with 17 water-solubleC₃–C₆ alkenes that have either been found in theatmosphere or are reasonable surrogates for identified species. Measured rateconstants ( $k_{\mathrm{ALK}+3{\mathrm{BP}}^{\ast }}$) vary by a factor of 30 and are in therange of (0.24–7.5) ×10⁹ M⁻¹ s⁻¹. Biogenic alkenesfound in the atmosphere – e.g., cis-3-hexen-1-ol, cis-3-hexenyl acetate, andmethyl jasmonate – react rapidly, with rate constants above 1×10⁹ M⁻¹ s⁻¹. Rate constants depend on alkene characteristicssuch as the location of the double bond, stereochemistry, and alkylsubstitution on the double bond. There is a reasonable correlation between $k_{\mathrm{ALK}+3{\mathrm{BP}}^{\ast }}$ and the calculated one-electron oxidation potential(OP) of the alkenes (R²=0.58); in contrast, rate constants are notcorrelated with bond dissociation enthalpies, bond dissociation freeenergies, or computed energy barriers for hydrogen abstraction. Using the OPrelationship, we estimate aqueous rate constants for a number of unsaturatedisoprene and limonene oxidation products with ³BP^∗: values are inthe range of (0.080–1.7) ×10⁹ M⁻¹ s⁻¹, withgenerally faster values for limonene products. Rate constants with lessreactive triplets, which are probably more environmentally relevant, arelikely roughly 25 times slower. Using our predicted rate constants, alongwith values for other reactions from the literature, we conclude thattriplets are probably minor oxidants for isoprene- and limonene-relatedcompounds in cloudy or foggy atmospheres, except in cases in which the tripletsare very reactive. 

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4. Electrochemical Ammonia Synthesis in a Proton-Conducting Ceramic Cell: A Parameter Study of an Iron-Based Electrode

   https://doi.org/10.1149/1945-7111/adfc9e  

   Blanck, Philipp; Martin, Etienne P; Schmider, Daniel; Kee, Robert J; Dailly, Julian; Deutschmann, Olaf (August 2025, Journal of The Electrochemical Society)

   Proton-conducting ceramic cells with a Ni-BaCe_0.8Zr_0.1Y_0.1O_3−δ|| BaCe_0.7Zr_0.2Y_0.1O_3−δ|| Fe/BaCe_0.7Zr_0.2Y_0.1O_3−δ-backbone structure were studied in a dual-chamber setup to evaluate the effects of temperature, gas flow, voltage, and electrolyte thickness on electrochemical ammonia synthesis. Three gas feed configurations were tested to differentiate surface reaction mechanisms. Thermodynamic calculations were conducted to evaluate the experimental results in the context of equilibrium limitations. The results showed that proton transport through the electrolyte plays a minor role in the formation of ammonia, while production rates correlated more strongly with applied voltage than with current density. Ammonia synthesis appeared significantly limited by thermodynamics, making an increased hydrogen partial pressure at the cathode essential. A feed configuration supplying only nitrogen to the cathode was ineffective, whereas introducing hydrogen increased the ammonia formation rate from 1.42 × 10⁻¹⁰mol cm⁻²s⁻¹to 3.23 × 10⁻⁹mol cm⁻²s⁻¹at −1.4 V and 500 °C. When proton conduction was suppressed under the same conditions, the rate further increased to 4.32 × 10⁻⁹mol cm⁻²s⁻¹. Varying the cathodic gas flow rate across the 12.57 cm²active area from 8 NL h⁻¹to 20 NL h⁻¹, the ammonia formation rate improved by a factor of 3.1 at −1 V, at both 500 °C and 600 °C. 

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5. Spectroscopic study of the 4f ⁷ 6s ^{2 8} S 7/2∘ – 4f ⁷ ( ⁸ S ^° ) 6s6p( ¹ P ^° ) ⁸ P _5/2,7/2 transitions in neutral europium-151 and europium-153: absolute frequency and hyperfine structure

   https://doi.org/10.1364/JOSAB.521181  

   Maruko, C; Çölmek, N N; Herd, M T; Ahrendsen, K J; Cabrales, B; Cannon, G; Davis, E; Guo, X Y; Karani, T; Wallace, A; et al (January 2024, Journal of the Optical Society of America B)

   We report on spectroscopic measurements on the 4f⁷6s²⁸S_7/2^∘−4f⁷(⁸S^∘)6s6p(¹P^∘)⁸P_5/2,7/2transitions at 466.32 nm and 462.85 nm, respectively, in neutral europium-151 and europium-153. The center of gravity frequencies for the 151 and 153 isotopes for both transitions are reported for the first time using saturated absorption spectroscopy. For the 6s6p(¹P^∘)⁸P_5/2state, the center of gravity frequencies were found to be 642,894,493.3(4) MHz and 642,891,693.3(9) MHz for the 151 and 153 isotopes, respectively. The hyperfine constants for the upper state were found to beA(151)=−157.01(3)MHz,B(151)=74.5(4)MHz andA(153)=−69.43(14)MHz,B(153)=191.0(26)MHz. These hyperfine values are all consistent with previously published results except forB(151) that has a small discrepancy. The isotope shift was found to be 2799.54(20) MHz, a small discrepancy with previously published results. For the 6s6p(¹P^∘)⁸P_7/2state, the center of gravity frequencies were found to be 647,708,930.6(6) MHz and 647,705,958.4(26) MHz for the 151 and 153 isotopes, respectively. The hyperfine constants for the upper state were found to beA(151)=−218.66(4)MHz,B(151)=−293.4(8)MHz andA(153)=−97.15(13)MHz,B(153)=−750(3)MHz. These values are all consistent with previously published results except forA(151) that has a small discrepancy. The isotope shift was found to be 2972.8(5) MHz, a small discrepancy with previously measured results. 

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